Fix raytracer bugs: BVH traversal, AABB transforms, root selection, and shading

- BVH: transform AABB using all 8 corners, fix leaf node traversal to check all primitives
- Node: reset AABB from primitive before transform, compute distance in world space
- Primitives: correct quadratic root selection (pick smallest positive), fix t-guards for Circle/RectangleXY, fix Torus AABB orientation
- Ray: fix random_unit_vec to cover all octants, compute reflection outside light loop, add indirect diffuse GI

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -1,41 +1,155 @@
-
 # Graphics Project
 
-This is my graphics project that I will be working on for A5
-I will use rlua for interacting with lua files
+# Introduction
 
-## Installation
+![image](img/img2.png)
 
-## Scripting
+This is a project I undertook at the University of Waterloo, where I first started using rust. Because of my inexperience, the code isn't as organised as it would be if I made it today and represents my first steps in computer graphics and the rust language.
 
-V()
-P()
-Scene()
-Scene.addNode()
-Scene.addLight()
-Node()
-Node.translate()
-Node.rotate()
-Node.scale()
-Camera()
-Light()
-Material()
-MaterialRed()
-MaterialBlue()
-MaterialGreen()
-MaterialMagenta()
-MaterialTurquoise()
-Sphere()
-SphereUnit()
-Cube()
-CubeUnit()
-Cone()
-ConeUnit()
-Cyclinder()
-//CylinderUnit()
-Circle()
-CircleUnit()
-Rectangle()
-RectangleUnit()
-Steiner()
-Torus()
+My unique aim was to perform ray intersections on special geometric surfaces, such as the CrossCap surface and the Steiner surface, hence those are among my _primitives_.
+
+# Installation
+
+Clone and run with `cargo run`, however much better performance will be granted with `cargo run --release`.
+
+![example](img/example.png)
+
+# Rhai
+
+Rhai is used as an interactive scripting lang for this project. Examples are found in `rhai/`.
+
+## Full List of rhai commands
+
+```
+/// Basic math types
+
+V(x : float, y : float, z : float) -> Vector3
+    // 3‑dimensional vector, used for directions, colors, etc.
+
+P(x : float, y : float, z : float) -> Position3
+    // 3‑dimensional position vector, used for points in space.
+
+
+/// Scene and graph
+
+Scene() -> Scene
+    // Create an empty scene with no nodes, lights, or camera.
+
+Scene.addNode(node : Node) -> void
+    // Add a node (with geometry or camera) to the scene.
+
+Scene.addLight(light : Light) -> void
+    // Add a light source to the scene.
+
+Scene.setCamera(camera : Camera) -> void
+    // Set the active camera for this scene.
+
+
+/// Nodes and transforms
+
+Node() -> Node
+    // Create an empty node (no mesh / camera / light by default).
+
+Node.translate(x : float, y : float, z : float) -> Node
+    // Apply translation by vector V(x, y, z) in local space, returns self for chaining.
+
+Node.rotate(x : float, y : float, z : float) -> Node
+    // Rotate node by Euler angles (in radians or degrees, implementation‑defined).
+
+Node.scale(x : float, y : float, z : float) -> Node
+    // Non‑uniform scale in local space.
+
+Node.setMaterial(material : Material) -> Node
+    // Set material for this node's mesh (if any).
+
+
+/// Camera
+
+Camera(position : P, target : P, up : V) -> Camera
+    // Create a camera located at `position`, looking at `target`, with `up` as the up direction.
+
+
+/// Lighting
+
+Ambient(color : V) -> AmbientLight
+    // Ambient light contribution with RGB in [0, 1].
+
+Light(position : P, color : V, falloff : V) -> PointLight
+    // Point light at `position` with RGB `color` and falloff parameters (constant, linear, quadratic).
+
+
+/// Materials
+
+Material(kd : V, ks : V, kr : V, shininess : float) -> Material
+    // Phong‑style material:
+    //   kd: diffuse color
+    //   ks: specular color
+    //   kr: reflection / mirror color
+    //   shininess: specular exponent.
+
+MaterialRed() -> Material
+MaterialBlue() -> Material
+MaterialGreen() -> Material
+MaterialMagenta() -> Material
+MaterialTurquoise() -> Material
+    // Convenience materials with predefined colors.
+
+
+/// Primitives
+
+Sphere(pos : P, radius : float) -> Mesh
+    // Sphere centered at `pos` with given radius.
+
+SphereUnit() -> Mesh
+    // Unit sphere at (0, 0, 0) with radius 1.
+
+Cube(pos : P, radius : float, normal : V) -> Mesh
+    // Cube centered at `pos`, edge length = 2 * radius (or radius, implementation‑defined),
+    // `normal` can define an orientation axis.
+
+CubeUnit() -> Mesh
+    // Unit cube at (0, 0, 0).
+
+Cone(radius : float, height : float) -> Mesh
+    // Cone aligned with +Z (for example), base radius and height.
+
+ConeUnit() -> Mesh
+    // Cone with radius 1 and height 1 at the origin.
+
+Cylinder(radius : float, height : float) -> Mesh
+    // Cylinder aligned with +Z, given radius and height.
+
+CylinderUnit() -> Mesh
+    // Cylinder with radius 1 and height 1 at the origin.
+
+Circle(position : P, radius : float, normal : V) -> Mesh
+    // Flat disk at `position` with `normal` orientation and given radius.
+
+CircleUnit() -> Mesh
+    // Unit circle in the XY plane at the origin.
+
+Rectangle(position : P, size : V, normal : V) -> Mesh
+    // Axis‑aligned rectangle centered at `position`, width/height from size.x / size.y, oriented by `normal`.
+
+RectangleUnit() -> Mesh
+    // 1x1 rectangle in the XY plane centered at origin.
+
+
+/// Special / parametric surfaces
+
+Steiner() -> Mesh
+    // A Steiner surface with default parameters and resolution.
+
+Torus(radiusMajor : float, radiusMinor : float) -> Mesh
+    // Torus with major and minor radius, centered at origin.
+
+Roman() -> Mesh
+    // Roman surface with default scale and resolution.
+
+CrossCap() -> Mesh
+    // Cross‑cap surface (Boy's surface variant / projective plane immersion).
+
+Gnonom() -> Mesh
+    // Gnomon‑like parametric surface (implementation‑defined shape).
+
+```

rhai/bvh_test.rhai

@@ -0,0 +1,81 @@
+// BVH Stress Test Scene - Grid of spheres
+let scene = Scene();
+
+// Camera
+let camera = Camera(P(0.0, 2.0, 5.0), P(0.0, 0.0, 0.0), V(0.0, 1.0, 0.0));
+scene.addCamera("main", camera);
+
+// Lights
+let light = Light(P(3.0, 5.0, 3.0), V(0.8, 0.8, 0.8), V(0.05, 0.05, 0.05));
+light.active(true);
+scene.addLight("key", light);
+
+let light2 = Light(P(-3.0, 4.0, -2.0), V(0.4, 0.4, 0.6), V(0.05, 0.05, 0.05));
+light2.active(true);
+scene.addLight("fill", light2);
+
+let ambient = Ambient(V(0.1, 0.1, 0.1));
+ambient.active(true);
+scene.addLight("ambient", ambient);
+
+// Materials
+let kd = V(0.8, 0.2, 0.2);
+let ks = V(0.3, 0.3, 0.3);
+let kr = V(0.0, 0.0, 0.0);
+let red = Material(kd, ks, kr, 10.0);
+scene.addMaterial("red", red);
+
+let kd = V(0.2, 0.2, 0.8);
+let ks = V(0.3, 0.3, 0.3);
+let kr = V(0.0, 0.0, 0.0);
+let blue = Material(kd, ks, kr, 10.0);
+scene.addMaterial("blue", blue);
+
+let kd = V(0.2, 0.8, 0.2);
+let ks = V(0.3, 0.3, 0.3);
+let kr = V(0.0, 0.0, 0.0);
+let green = Material(kd, ks, kr, 10.0);
+scene.addMaterial("green", green);
+
+let kd = V(0.8, 0.8, 0.2);
+let ks = V(0.3, 0.3, 0.3);
+let kr = V(0.0, 0.0, 0.0);
+let yellow = Material(kd, ks, kr, 10.0);
+scene.addMaterial("yellow", yellow);
+
+let kd = V(0.8, 0.4, 0.8);
+let ks = V(0.3, 0.3, 0.3);
+let kr = V(0.1, 0.1, 0.1);
+let purple = Material(kd, ks, kr, 15.0);
+scene.addMaterial("purple", purple);
+
+// Floor
+let floor = RectangleUnit();
+let floor_node = Node(floor, green);
+floor_node.rotate(-90.0, 0.0, 0.0);
+floor_node.translate(0.0, -1.5, 0.0);
+floor_node.scale(5.0, 5.0, 1.0);
+scene.addNode("floor", floor_node);
+
+// Grid of spheres: 5 x 4 x 5 = 100 spheres
+let materials = [red, blue, green, yellow, purple];
+let count = 0;
+
+for x in range(-2, 3) {
+    for y in range(0, 4) {
+        for z in range(-2, 3) {
+            let mat_idx = count % 5;
+            let mat = materials[mat_idx];
+            let sphere = Sphere(P(0.0, 0.0, 0.0), 0.15);
+            let node = Node(sphere, mat);
+            let px = x.to_float() * 0.7;
+            let py = y.to_float() * 0.7 - 1.0;
+            let pz = z.to_float() * 0.7 - 1.0;
+            node.translate(px, py, pz);
+            scene.addNode("s" + count, node);
+            count += 1;
+        }
+    }
+}
+
+scene

src/bvh.rs

@@ -21,8 +21,8 @@ pub struct AABB {
 impl AABB {
     // New box with respective coordinates
     pub fn new(bln: Point3<f64>, trf: Point3<f64>) -> AABB {
-        let bln = bln + Vector3::new(EPSILON, EPSILON, EPSILON);
-        let trf = trf - Vector3::new(EPSILON, EPSILON, EPSILON);
+        let bln = bln - Vector3::new(EPSILON, EPSILON, EPSILON);
+        let trf = trf + Vector3::new(EPSILON, EPSILON, EPSILON);
         let centroid = bln + (trf - bln) / 2.0;
         AABB { bln, trf, centroid }
     }
@@ -36,64 +36,46 @@ impl AABB {
     }
     //Apply a matrix transformation to a box
     pub fn transform_mut(&mut self, mat: &Matrix4<f64>) {
-        let bln = &mut self.bln;
-        let trf = &mut self.trf;
-        let centroid = &mut self.centroid;
-        self.bln = mat.transform_point(bln);
-        self.trf = mat.transform_point(trf);
-        self.centroid = mat.transform_point(centroid);
+        let corners = [
+            Point3::new(self.bln.x, self.bln.y, self.bln.z),
+            Point3::new(self.trf.x, self.bln.y, self.bln.z),
+            Point3::new(self.bln.x, self.trf.y, self.bln.z),
+            Point3::new(self.trf.x, self.trf.y, self.bln.z),
+            Point3::new(self.bln.x, self.bln.y, self.trf.z),
+            Point3::new(self.trf.x, self.bln.y, self.trf.z),
+            Point3::new(self.bln.x, self.trf.y, self.trf.z),
+            Point3::new(self.trf.x, self.trf.y, self.trf.z),
+        ];
+        let mut new_bln = Point3::new(f64::MAX, f64::MAX, f64::MAX);
+        let mut new_trf = Point3::new(f64::MIN, f64::MIN, f64::MIN);
+        for corner in &corners {
+            let t = mat.transform_point(corner);
+            new_bln = new_bln.inf(&t);
+            new_trf = new_trf.sup(&t);
+        }
+        self.bln = new_bln;
+        self.trf = new_trf;
+        self.centroid = self.bln + (self.trf - self.bln) / 2.0;
     }
     // Intersect bounding box exactly
     pub fn intersect_ray(&self, ray: &Ray) -> bool {
-        let bln = &self.bln;
-        let trf = &self.trf;
-        let t1 = (bln - ray.a).component_div(&ray.b);
-        let t2 = (trf - ray.a).component_div(&ray.b);
+        let t1 = (self.bln - ray.a).component_div(&ray.b);
+        let t2 = (self.trf - ray.a).component_div(&ray.b);
 
-        let tmin = t1.inf(&t2).min();
-        let tmax = t1.sup(&t2).max();
+        let tmin = t1.inf(&t2).max();
+        let tmax = t1.sup(&t2).min();
 
-        if tmax >= tmin {
-            let intersect = ray.at_t(tmin);
-
-            // Check if the intersection is inside the box
-            if intersect.x > bln.x
-                || intersect.x < trf.x
-                || intersect.y > bln.y
-                || intersect.y < trf.y
-                || intersect.z > bln.z
-                || intersect.z < trf.z
-            {
-                return true; // Intersection is outside the box
-            }
-        }
-        false
+        tmax >= tmin && tmax > 0.0
     }
-    // Intersect way with some epsilon term
+    // Intersect with some epsilon tolerance
     pub fn intersect_ray_aprox(&self, ray: &Ray) -> bool {
-        let bln = &self.bln;
-        let trf = &self.trf;
-        let t1 = (bln - ray.a).component_div(&ray.b);
-        let t2 = (trf - ray.a).component_div(&ray.b);
+        let t1 = (self.bln - ray.a).component_div(&ray.b);
+        let t2 = (self.trf - ray.a).component_div(&ray.b);
 
-        let tmin = t1.inf(&t2).min();
-        let tmax = t1.sup(&t2).max();
+        let tmin = t1.inf(&t2).max();
+        let tmax = t1.sup(&t2).min();
 
-        if tmax >= tmin {
-            let intersect = ray.at_t(tmin);
-
-            // Check if the intersection is inside the box
-            if intersect.x > bln.x - EPSILON
-                || intersect.x < trf.x + EPSILON
-                || intersect.y > bln.y - EPSILON
-                || intersect.y < trf.y + EPSILON
-                || intersect.z > bln.z - EPSILON
-                || intersect.z < trf.z + EPSILON
-            {
-                return true; // Intersection is outside the box
-            }
-        }
-        false
+        tmax >= tmin - EPSILON && tmax > 0.0
     }
     // Get the center of this bounding box
     fn get_centroid(&self) -> Point3<f64> {
@@ -126,6 +108,7 @@ impl AABB {
             self.trf.y.max(other.trf.y),
             self.trf.z.max(other.trf.z),
         );
+        self.centroid = self.bln + (self.trf - self.bln) / 2.0;
     }
     //Grow the AABB to contain the cover the point
     pub fn grow(&self, other: &Point3<f64>) -> AABB {
@@ -154,6 +137,7 @@ impl AABB {
             self.trf.y.max(other.y),
             self.trf.z.max(other.z),
         );
+        self.centroid = self.bln + (self.trf - self.bln) / 2.0;
     }
     // Size of AABB
     pub fn size(&self) -> Vector3<f64> {
@@ -304,7 +288,7 @@ impl BVH {
         // let mut best_pos = 0.0;
         // let mut best_cost = 1e30;
         // let first_prim_idx = self.bvh_nodes[index].first_prim;
-        // for axis in 0..2 {
+        // for axis in 0..3 {
         //     for i in 0..self.bvh_nodes[index].prim_count {
         //         let node = &self.nodes[first_prim_idx + i];
         //         //Get the centroid of the bounding box
@@ -391,20 +375,22 @@ impl BVH {
             return None;
         }
         if bvh_node.prim_count != 0 {
-            // Leaf node intersection
-            let node_idx = bvh_node.first_prim;
-            let node = &self.nodes[node_idx];
-            if !node.active {
-                return None;
-            }
-            if let Some(intersect) = node.intersect_ray(&ray) {
-                if intersect.distance < EPSILON {
-                    return None;
-                } else {
-                    return Some((node, intersect));
+            // Leaf node - check all primitives it contains
+            let mut closest: Option<(&Node, Intersection)> = None;
+            let mut closest_dist = f64::MAX;
+            for i in 0..bvh_node.prim_count {
+                let node = &self.nodes[bvh_node.first_prim + i];
+                if !node.active {
+                    continue;
+                }
+                if let Some(intersect) = node.intersect_ray(&ray) {
+                    if intersect.distance >= EPSILON && intersect.distance < closest_dist {
+                        closest_dist = intersect.distance;
+                        closest = Some((node, intersect));
+                    }
                 }
             }
-            return None;
+            return closest;
         } else {
             //Recurse down the BVH
             //Recurse down the BVH right node
@@ -438,17 +424,14 @@ impl BVH {
             let aabb = self.nodes[node.first_prim + i].get_world_aabb();
             if aabb.trf[axis] < pos {
                 l_count += 1;
-                l_aabb.grow_mut(&aabb.trf);
+                l_aabb.join_mut(&aabb);
             } else {
                 r_count += 1;
-                r_aabb.grow_mut(&aabb.bln);
+                r_aabb.join_mut(&aabb);
             }
         }
         let cost = l_count as f64 * l_aabb.area() + r_count as f64 * r_aabb.area();
-        match cost > 0.0 {
-            true => 0.0,
-            false => 1e30,
-        }
+        if cost > 0.0 { cost } else { 1e30 }
     }
 }
 

src/camera.rs

@@ -51,6 +51,66 @@ impl Camera {
         self.recalculate_matrix();
     }
 
+    /// Get the forward direction vector (from eye toward target)
+    pub fn forward(&self) -> Vector3<f64> {
+        (self.target - self.eye).normalize()
+    }
+
+    /// Get the right direction vector
+    pub fn right(&self) -> Vector3<f64> {
+        self.forward().cross(&self.up).normalize()
+    }
+
+    /// Move the camera forward/backward along its view direction (moves both eye and target)
+    pub fn move_forward(&mut self, amount: f64) {
+        let dir = self.forward() * amount;
+        self.eye += dir;
+        self.target += dir;
+        self.recalculate_matrix();
+    }
+
+    /// Strafe the camera left/right (moves both eye and target)
+    pub fn move_right(&mut self, amount: f64) {
+        let dir = self.right() * amount;
+        self.eye += dir;
+        self.target += dir;
+        self.recalculate_matrix();
+    }
+
+    /// Move the camera up/down along the up vector (moves both eye and target)
+    pub fn move_up(&mut self, amount: f64) {
+        let dir = self.up.normalize() * amount;
+        self.eye += dir;
+        self.target += dir;
+        self.recalculate_matrix();
+    }
+
+    /// Orbit the camera around the target point by yaw (horizontal) and pitch (vertical) angles in radians
+    pub fn orbit(&mut self, yaw: f64, pitch: f64) {
+        let offset = self.eye - self.target;
+        let radius = offset.norm();
+
+        // Current spherical angles
+        let current_pitch = (offset.y / radius).asin();
+        let current_yaw = offset.z.atan2(offset.x);
+
+        let new_yaw = current_yaw + yaw;
+        let new_pitch = (current_pitch + pitch).clamp(
+            -std::f64::consts::FRAC_PI_2 + 0.01,
+            std::f64::consts::FRAC_PI_2 - 0.01,
+        );
+
+        // Convert back to cartesian
+        let new_offset = Vector3::new(
+            radius * new_pitch.cos() * new_yaw.cos(),
+            radius * new_pitch.sin(),
+            radius * new_pitch.cos() * new_yaw.sin(),
+        );
+
+        self.eye = self.target + new_offset;
+        self.recalculate_matrix();
+    }
+
     /// Recalculate the view and inverse view matrices based on the current eye, target, and up vectors
     fn recalculate_matrix(&mut self) {
         self._view = Matrix4::look_at_lh(&self.eye, &self.target, &self.up);

src/gui.rs

@@ -11,7 +11,7 @@ use imgui::*;
 use nalgebra::{Point3, Vector3};
 use pixels::{wgpu, PixelsContext};
 use rhai::Engine;
-use std::time::Instant;
+use std::time::{Duration, Instant};
 
 //BUFFER CONSTANTS
 const BUFFER_PROPORTION_MIN: f32 = 0.1;
@@ -38,22 +38,16 @@ const MIN_DIFFUSE_COEFFICIENT: f32 = 0.0;
 const MAX_DIFFUSE_COEFFICIENT: f32 = 1.0;
 
 //MATERIAL CONSTANTS
-const MIN_D: f32 = 0.0;
-const MIN_S: f32 = 0.0;
 const MIN_SHINE: f32 = 0.0;
-const MAX_D: f32 = 1.0;
-const MAX_S: f32 = 1.0;
 const MAX_SHINE: f32 = 50.0;
 
 //TRANSFORMATION CONSTANTS
-const MIN_COLOUR: f32 = 0.0;
 const MIN_FALLOFF: f32 = 0.0;
 const MIN_SCALE: f64 = 0.0;
 //const MIN_POSITION: f64 = -10.0;
 const MIN_ROTATION: f64 = -180.0;
 const MIN_TRANSLATE: f64 = -10.0;
 //--
-const MAX_COLOUR: f32 = 1.0;
 const MAX_FALLOFF: f32 = 1.0;
 const MAX_SCALE: f64 = 3.0;
 //const MAX_POSITION: f64 = 10.0;
@@ -81,6 +75,9 @@ pub struct Gui {
 
     pub event: Option<GuiEvent>,
 
+    render_start: Option<Instant>,
+    render_elapsed: Option<Duration>,
+
     script_filename: String,
     script: String,
     engine: Engine,
@@ -141,6 +138,9 @@ impl Gui {
             last_cursor: None,
             event: None,
 
+            render_start: None,
+            render_elapsed: None,
+
             script_filename: String::from(INIT_FILE),
             script: String::new(),
             engine: init_engine(),
@@ -171,6 +171,17 @@ impl Gui {
         gui
     }
 
+    pub fn start_render_timer(&mut self) {
+        self.render_start = Some(Instant::now());
+        self.render_elapsed = None;
+    }
+
+    pub fn stop_render_timer(&mut self) {
+        if let Some(start) = self.render_start.take() {
+            self.render_elapsed = Some(start.elapsed());
+        }
+    }
+
     /// Prepare Dear ImGui.
     pub fn prepare(
         &mut self,
@@ -216,25 +227,42 @@ impl Gui {
                 &mut self.raytracing_option.threads,
             );
             // Numbers of rays to render per pass
-            ui.slider(
-                "Rays Per Pass",
-                RAYS_MIN,
-                RAYS_MAX,
-                &mut self.raytracing_option.pixels_per_thread,
-            );
+            Drag::new("Rays Per Pass")
+                .range(RAYS_MIN, RAYS_MAX)
+                .speed(50.0)
+                .build(ui, &mut self.raytracing_option.pixels_per_thread);
             // Proportion of the window the buffer occupies
-            ui.slider(
-                "% Buffer: ",
-                BUFFER_PROPORTION_MIN,
-                BUFFER_PROPORTION_MAX,
-                &mut self.raytracing_option.buffer_proportion,
-            );
+            Drag::new("% Buffer: ")
+                .range(BUFFER_PROPORTION_MIN, BUFFER_PROPORTION_MAX)
+                .speed(0.005)
+                .display_format("%.2f")
+                .build(ui, &mut self.raytracing_option.buffer_proportion);
             //Clear colour for scene
-            ui.slider_config("Clear Colour", 0, 255)
-                .build_array(&mut self.raytracing_option.clear_color);
+            let mut clear_f32 = [
+                self.raytracing_option.clear_color[0] as f32 / 255.0,
+                self.raytracing_option.clear_color[1] as f32 / 255.0,
+                self.raytracing_option.clear_color[2] as f32 / 255.0,
+                self.raytracing_option.clear_color[3] as f32 / 255.0,
+            ];
+            if ui.color_edit4_config("Clear Colour", &mut clear_f32).alpha_bar(true).build() {
+                self.raytracing_option.clear_color = [
+                    (clear_f32[0] * 255.0) as u8, (clear_f32[1] * 255.0) as u8,
+                    (clear_f32[2] * 255.0) as u8, (clear_f32[3] * 255.0) as u8,
+                ];
+            }
             //Clear colour if no intersect
-            ui.slider_config("Pixel Clear Colour", 0, 255)
-                .build_array(&mut self.raytracing_option.pixel_clear);
+            let mut pixel_clear_f32 = [
+                self.raytracing_option.pixel_clear[0] as f32 / 255.0,
+                self.raytracing_option.pixel_clear[1] as f32 / 255.0,
+                self.raytracing_option.pixel_clear[2] as f32 / 255.0,
+                self.raytracing_option.pixel_clear[3] as f32 / 255.0,
+            ];
+            if ui.color_edit4_config("Pixel Clear Colour", &mut pixel_clear_f32).alpha_bar(true).build() {
+                self.raytracing_option.pixel_clear = [
+                    (pixel_clear_f32[0] * 255.0) as u8, (pixel_clear_f32[1] * 255.0) as u8,
+                    (pixel_clear_f32[2] * 255.0) as u8, (pixel_clear_f32[3] * 255.0) as u8,
+                ];
+            }
             //Ray depth slider
             ui.slider(
                 "Ray Depth",
@@ -250,12 +278,11 @@ impl Gui {
                 &mut self.raytracing_option.ray_samples,
             );
             //Ray randomness
-            ui.slider(
-                "Ray Randomness",
-                MIN_RANDOM,
-                MAX_RANDOM,
-                &mut self.raytracing_option.ray_randomness,
-            );
+            Drag::new("Ray Randomness")
+                .range(MIN_RANDOM, MAX_RANDOM)
+                .speed(5.0)
+                .display_format("%.1f")
+                .build(ui, &mut self.raytracing_option.ray_randomness);
             //Number of diffuse rays
             ui.slider(
                 "Diffuse Rays",
@@ -264,12 +291,11 @@ impl Gui {
                 &mut self.raytracing_option.diffuse_rays,
             );
             //Diffuse Coefficient
-            ui.slider(
-                "Diffuse Coefficient",
-                MIN_DIFFUSE_COEFFICIENT,
-                MAX_DIFFUSE_COEFFICIENT,
-                &mut self.raytracing_option.diffuse_coefficient,
-            );
+            Drag::new("Diffuse Coefficient")
+                .range(MIN_DIFFUSE_COEFFICIENT, MAX_DIFFUSE_COEFFICIENT)
+                .speed(0.005)
+                .display_format("%.3f")
+                .build(ui, &mut self.raytracing_option.diffuse_coefficient);
             // Fov of the buffer
             ui.slider(
                 "fov",
@@ -283,6 +309,15 @@ impl Gui {
             ui.checkbox("Enable Reflections", &mut self.raytracing_option.reflect);
             ui.checkbox("Enable Specular", &mut self.raytracing_option.specular);
             ui.checkbox("Enable Diffuse", &mut self.raytracing_option.diffuse);
+            // Render timer display
+            ui.separator();
+            if let Some(start) = &self.render_start {
+                let elapsed = start.elapsed().as_secs_f64();
+                ui.text(format!("Rendering: {:.2}s", elapsed));
+            } else if let Some(elapsed) = &self.render_elapsed {
+                ui.text(format!("Render time: {:.2}s", elapsed.as_secs_f64()));
+            }
+            ui.separator();
             // Apply stored changes
             if ui.button("Apply") {
                 self.event = Some(GuiEvent::RaytracerOption(self.raytracing_option.clone()));
@@ -292,12 +327,21 @@ impl Gui {
         if CollapsingHeader::new("Camera").build(ui) {
             // Eye, target and up vector inputs
             ui.text("Camera options:");
-            ui.slider_config("Eye", MIN_TRANSLATE, MAX_TRANSLATE)
-                .build_array(self.camera.eye.coords.as_mut_slice());
-            ui.slider_config("Target", MIN_TRANSLATE, MAX_TRANSLATE)
-                .build_array(self.camera.target.coords.as_mut_slice());
-            ui.slider_config("Up", 0.0, 1.0)
-                .build_array(self.camera.up.as_mut_slice());
+            Drag::new("Eye")
+                .range(MIN_TRANSLATE, MAX_TRANSLATE)
+                .speed(0.05)
+                .display_format("%.2f")
+                .build_array(ui, self.camera.eye.coords.as_mut_slice());
+            Drag::new("Target")
+                .range(MIN_TRANSLATE, MAX_TRANSLATE)
+                .speed(0.05)
+                .display_format("%.2f")
+                .build_array(ui, self.camera.target.coords.as_mut_slice());
+            Drag::new("Up")
+                .range(0.0, 1.0)
+                .speed(0.005)
+                .display_format("%.3f")
+                .build_array(ui, self.camera.up.as_mut_slice());
             if ui.button("Apply Camera") {
                 println!("Camera changed");
                 self.event = Some(GuiEvent::CameraUpdate(self.camera.clone()));
@@ -361,12 +405,21 @@ impl Gui {
                     ui.checkbox(format!("##active{label}"), &mut node.active);
                     ui.same_line();
                     if let Some(_t) = ui.tree_node(label) {
-                        ui.slider_config("Translation", MIN_TRANSLATE, MAX_TRANSLATE)
-                            .build_array(&mut node.translation);
-                        ui.slider_config("Rotation", MIN_ROTATION, MAX_ROTATION)
-                            .build_array(&mut node.rotation);
-                        ui.slider_config("Scale", MIN_SCALE, MAX_SCALE)
-                            .build_array(&mut node.scale);
+                        Drag::new("Translation")
+                            .range(MIN_TRANSLATE, MAX_TRANSLATE)
+                            .speed(0.05)
+                            .display_format("%.2f")
+                            .build_array(ui, &mut node.translation);
+                        Drag::new("Rotation")
+                            .range(MIN_ROTATION, MAX_ROTATION)
+                            .speed(1.0)
+                            .display_format("%.1f")
+                            .build_array(ui, &mut node.rotation);
+                        Drag::new("Scale")
+                            .range(MIN_SCALE, MAX_SCALE)
+                            .speed(0.01)
+                            .display_format("%.3f")
+                            .build_array(ui, &mut node.scale);
                     }
                 }
             }
@@ -374,11 +427,19 @@ impl Gui {
             if let Some(_t) = ui.tree_node("Materials") {
                 for (label, material) in &mut self.scene.materials {
                     if let Some(_t) = ui.tree_node(label) {
-                        ui.slider_config("ks", MIN_D, MAX_D)
-                            .build_array(material.ks.as_mut_slice());
-                        ui.slider_config("kd", MIN_S, MAX_S)
-                            .build_array(material.kd.as_mut_slice());
-                        ui.slider("shine", MIN_SHINE, MAX_SHINE, &mut material.shininess);
+                        let mut ks_arr: [f32; 3] = material.ks.into();
+                        if ui.color_edit3("ks", &mut ks_arr) {
+                            material.ks = Vector3::from(ks_arr);
+                        }
+                        let mut kd_arr: [f32; 3] = material.kd.into();
+                        if ui.color_edit3("kd", &mut kd_arr) {
+                            material.kd = Vector3::from(kd_arr);
+                        }
+                        Drag::new("shine")
+                            .range(MIN_SHINE, MAX_SHINE)
+                            .speed(0.5)
+                            .display_format("%.1f")
+                            .build(ui, &mut material.shininess);
                     }
                 }
             }
@@ -388,12 +449,20 @@ impl Gui {
                     ui.checkbox(format!("##activelight{label}"), &mut light.active);
                     ui.same_line();
                     if let Some(_t) = ui.tree_node(label) {
-                        ui.slider_config("Colour", MIN_COLOUR, MAX_COLOUR)
-                            .build_array(light.colour.as_mut_slice());
-                        ui.slider_config("Position", MIN_TRANSLATE, MAX_TRANSLATE)
-                            .build_array(light.position.coords.as_mut_slice());
-                        ui.slider_config("Falloff", MIN_FALLOFF, MAX_FALLOFF)
-                            .build_array(light.falloff.as_mut_slice());
+                        let mut colour_arr: [f32; 3] = light.colour.into();
+                        if ui.color_edit3("Colour", &mut colour_arr) {
+                            light.colour = Vector3::from(colour_arr);
+                        }
+                        Drag::new("Position")
+                            .range(MIN_TRANSLATE, MAX_TRANSLATE)
+                            .speed(0.05)
+                            .display_format("%.2f")
+                            .build_array(ui, light.position.coords.as_mut_slice());
+                        Drag::new("Falloff")
+                            .range(MIN_FALLOFF, MAX_FALLOFF)
+                            .speed(0.005)
+                            .display_format("%.3f")
+                            .build_array(ui, light.falloff.as_mut_slice());
                     }
                 }
             }
@@ -430,6 +499,11 @@ impl Gui {
         )
     }
 
+    /// Update the GUI's camera to reflect external changes (e.g. from keyboard/mouse movement)
+    pub fn update_camera(&mut self, camera: &Camera) {
+        self.camera = camera.clone();
+    }
+
     /// Handle any outstanding events.
     pub fn handle_event(
         &mut self,

src/node.rs

@@ -99,17 +99,19 @@ impl Node {
         // Compute the inverse model matrix by inverting the model matrix
         self.inv_model = self.model.try_inverse().unwrap();
         self.inv_transpose_model = self.inv_model.transpose().remove_row(3).remove_column(3);
+        // Reset AABB from primitive local space before transforming to world space
+        self.aabb = self.primitive.get_aabb();
         self.aabb.transform_mut(&self.model);
     }
     // Intersection of a ray, will convert to model coords and check
     pub fn intersect_ray(&self, ray: &Ray) -> Option<Intersection> {
-        let ray = ray.transform(&self.inv_model); //Transform from world coordinates
-        if let Some(mut intersect) = self.primitive.intersect_ray(&ray) {
+        let local_ray = ray.transform(&self.inv_model); //Transform from world coordinates
+        if let Some(mut intersect) = self.primitive.intersect_ray(&local_ray) {
             if intersect.distance < EPSILON {
                 return None;
             }
             intersect.transform_mut(&self.model, &self.inv_transpose_model); //Transform to world coords
-            intersect.distance = distance(&intersect.point, &ray.a);
+            intersect.distance = distance(&intersect.point, &ray.a); // use world-space ray origin
             return Some(intersect);
         }
         return None;

src/primitive.rs

@@ -47,14 +47,13 @@ impl Primitive for Sphere {
             Roots::No(_) => return None,
             Roots::One([x1]) => x1,
             Roots::Two([x1, x2]) => {
+                // roots are returned in ascending order: x1 <= x2
                 if x1 <= 0.0 && x2 <= 0.0 {
                     return None;
+                } else if x1 <= 0.0 {
+                    x2
                 } else {
-                    if x1.abs() < x2.abs() {
-                        x1
-                    } else {
-                        x2
-                    }
+                    x1
                 }
             }
             _ => return None,
@@ -124,9 +123,9 @@ impl Primitive for Circle {
         let n_dot_b = ray.b.dot(&self.normal);
         let t = (self.constant - n_dot_a) / n_dot_b;
 
-        if t > INFINITY {
+        if t <= 0.0 || t > INFINITY {
             return None;
-        };
+        }
 
         let intersect = ray.at_t(t);
         //Distance to center of circle
@@ -197,14 +196,13 @@ impl Primitive for Cylinder {
             Roots::No(_) => return None,
             Roots::One([x1]) => Some(x1),
             Roots::Two([x1, x2]) => {
+                // roots are returned in ascending order: x1 <= x2
                 if x1 <= 0.0 && x2 <= 0.0 {
                     return None;
+                } else if x1 <= 0.0 {
+                    Some(x2)
                 } else {
-                    if x1.abs() < x2.abs() {
-                        Some(x1)
-                    } else {
-                        Some(x2)
-                    }
+                    Some(x1)
                 }
             }
             _ => return None,
@@ -325,14 +323,13 @@ impl Primitive for Cone {
             Roots::No(_) => None,
             Roots::One([x1]) => Some(x1),
             Roots::Two([x1, x2]) => {
+                // roots are returned in ascending order: x1 <= x2
                 if x1 <= 0.0 && x2 <= 0.0 {
                     None
+                } else if x1 <= 0.0 {
+                    Some(x2)
                 } else {
-                    if x1.abs() < x2.abs() {
-                        Some(x1)
-                    } else {
-                        Some(x2)
-                    }
+                    Some(x1)
                 }
             }
             _ => None,
@@ -359,7 +356,15 @@ impl Primitive for Cone {
             (None, None) => None,
             (Some(cone_intersect), None) => Some(cone_intersect),
             (None, Some(circle_intersect)) => Some(circle_intersect),
-            (Some(cone_intersect), Some(_)) => Some(cone_intersect),
+            (Some(cone_intersect), Some(circle_intersect)) => {
+                let cone_dist = distance(&ray.a, &cone_intersect.point);
+                let circle_dist = distance(&ray.a, &circle_intersect.point);
+                if cone_dist < circle_dist {
+                    Some(cone_intersect)
+                } else {
+                    Some(circle_intersect)
+                }
+            }
         }
     }
 
@@ -395,7 +400,7 @@ impl Primitive for RectangleXY {
         let az = ray.a.z;
         let bz = ray.b.z;
         let t = (z - az) / bz;
-        if t > INFINITY {
+        if t <= 0.0 || t > INFINITY {
             return None;
         }
         let intersect = ray.at_t(t);
@@ -470,21 +475,28 @@ impl Primitive for Cube {
                 return None; // Intersection is outside the box
             }
 
-            //Get normal of intersection point
-            //t1 is bln t2 is trf
-            let normal = if tmin == t1.x {
-                Vector3::new(-1.0, 0.0, 0.0)
-            } else if tmin == t1.y {
-                Vector3::new(0.0, -1.0, 0.0)
-            } else if tmin == t1.z {
-                Vector3::new(0.0, 0.0, -1.0)
-            } else if tmin == t2.x {
-                Vector3::new(1.0, 0.0, 0.0)
-            } else if tmin == t2.y {
-                Vector3::new(0.0, 1.0, 0.0)
-            } else {
-                Vector3::new(0.0, 0.0, 1.0)
-            };
+            // Determine which face was hit by finding the t-value closest to tmin
+            let diffs = [
+                (t1.x - tmin).abs(),
+                (t1.y - tmin).abs(),
+                (t1.z - tmin).abs(),
+                (t2.x - tmin).abs(),
+                (t2.y - tmin).abs(),
+                (t2.z - tmin).abs(),
+            ];
+            let normals = [
+                Vector3::new(-1.0, 0.0, 0.0),
+                Vector3::new(0.0, -1.0, 0.0),
+                Vector3::new(0.0, 0.0, -1.0),
+                Vector3::new(1.0, 0.0, 0.0),
+                Vector3::new(0.0, 1.0, 0.0),
+                Vector3::new(0.0, 0.0, 1.0),
+            ];
+            let min_idx = diffs.iter()
+                .enumerate()
+                .min_by(|(_, a), (_, b)| a.partial_cmp(b).unwrap())
+                .unwrap().0;
+            let normal = normals[min_idx];
 
             Some(Intersection {
                 point: intersect,
@@ -645,9 +657,9 @@ impl Mesh {
                                 let u = vertices[v1 - 1];
                                 let v = vertices[v2 - 1];
                                 let w = vertices[v3 - 1];
-                                let uv = u - v;
-                                let uw = w - v;
-                                let normal = uv.cross(&uw).normalize();
+                                let uv = v - u;
+                                let uw = w - u;
+                                let normal = uw.cross(&uv).normalize();
                                 triangles.push(Triangle { u, v, w, normal });
                             }
                         }
@@ -805,9 +817,9 @@ impl Primitive for Torus {
     }
 
     fn get_aabb(&self) -> AABB {
-        //TODO!
-        let trf = Point3::new(1.0, 1.0, 1.0);
-        let bln = Point3::new(-1.0, -1.0, -1.0);
+        let extent = self.inner_rad + self.outer_rad;
+        let bln = Point3::new(-extent, -extent, -self.outer_rad);
+        let trf = Point3::new(extent, extent, self.outer_rad);
         AABB::new(bln, trf)
     }
 }
@@ -846,19 +858,19 @@ impl Gnonom {
 
 impl Primitive for Gnonom {
     fn intersect_ray(&self, ray: &Ray) -> Option<Intersection> {
-        match self.x_cube.intersect_ray(ray) {
-            Some(intersect) => return Some(intersect),
-            None => (),
-        };
-        match self.y_cube.intersect_ray(ray) {
-            Some(intersect) => return Some(intersect),
-            None => (),
-        };
-        match self.z_cube.intersect_ray(ray) {
-            Some(intersect) => return Some(intersect),
-            None => (),
-        };
-        None
+        let mut closest: Option<Intersection> = None;
+        let mut closest_dist = f64::MAX;
+
+        for cube in [&self.x_cube, &self.y_cube, &self.z_cube] {
+            if let Some(intersect) = cube.intersect_ray(ray) {
+                let dist = distance(&ray.a, &intersect.point);
+                if dist < closest_dist {
+                    closest_dist = dist;
+                    closest = Some(intersect);
+                }
+            }
+        }
+        closest
     }
 
     fn get_aabb(&self) -> AABB {

src/ray.rs

@@ -3,7 +3,11 @@ use nalgebra::{distance, Matrix3, Matrix4, Point3, Vector3};
 use rand;
 
 fn random_vec() -> Vector3<f64> {
-    Vector3::new(rand::random(), rand::random(), rand::random())
+    Vector3::new(
+        rand::random::<f64>() * 2.0 - 1.0,
+        rand::random::<f64>() * 2.0 - 1.0,
+        rand::random::<f64>() * 2.0 - 1.0,
+    )
 }
 fn random_unit_vec() -> Vector3<f64> {
     random_vec().normalize()
@@ -165,9 +169,30 @@ impl Ray {
         let incidence = &ray.b;
         let material = &node.material;
 
-        // Compute the ambient light component and set it as base colour
         let mut colour = Vector3::zeros();
 
+        // Reflection is view-dependent, not light-dependent — compute once
+        let mut reflect = Vector3::zeros();
+        if options.reflect {
+            let reflect_dir = incidence - 2.0 * incidence.dot(&normal) * normal;
+            let reflect_ray = Ray::new(*point, reflect_dir);
+            if let Some(col) = reflect_ray.shade_ray(scene, depth + 1, options, bvh) {
+                reflect += col.component_mul(&material.kr)
+            }
+        }
+
+        // Indirect diffuse (global illumination samples) — compute once
+        let mut indirect = Vector3::zeros();
+        if options.diffuse {
+            for _ in 0..options.diffuse_rays {
+                let diffuse_dir = random_unit_vec();
+                let diffuse_ray = Ray::new(point.clone(), diffuse_dir + normal);
+                if let Some(col) = diffuse_ray.shade_ray(scene, depth + 1, options, bvh) {
+                    indirect += col * options.diffuse_coefficient;
+                }
+            }
+        }
+
         for (_, light) in &scene.lights {
             if !light.active {
                 continue;
@@ -192,27 +217,10 @@ impl Ray {
 
             let n_dot_l = normal.dot(&to_light).max(0.0) as f32;
 
-            //Reflected component
-            let mut reflect = Vector3::zeros();
-            if options.reflect {
-                let reflect_dir = incidence - 2.0 * incidence.dot(&normal) * normal;
-                let reflect_ray = Ray::new(*point, reflect_dir);
-                if let Some(col) = reflect_ray.shade_ray(scene, depth + 1, options, bvh) {
-                    reflect += col.component_mul(&material.kr)
-                }
-            }
-
-            //Diffuse component (Lambertian)
+            //Direct diffuse component (Lambertian)
             let mut diffuse = Vector3::zeros();
             if options.diffuse {
                 diffuse += material.kd * n_dot_l;
-                for _ in 0..options.diffuse_rays {
-                    let diffuse_dir = random_unit_vec();
-                    let diffuse_ray = Ray::new(point.clone(), diffuse_dir + normal);
-                    if let Some(col) = diffuse_ray.shade_ray(scene, depth + 1, options, bvh) {
-                        diffuse += col * options.diffuse_coefficient;
-                    }
-                }
             }
 
             //Specular component
@@ -234,10 +242,13 @@ impl Ray {
                         + light.falloff[2] * light_distance * light_distance);
             }
 
-            let intensity = light.colour.component_mul(&(diffuse + reflect + specular)) * falloff;
+            let intensity = light.colour.component_mul(&(diffuse + specular)) * falloff;
             colour += &intensity;
         }
 
+        // Add light-independent terms
+        colour += reflect + indirect;
+
         colour
     }
 
@@ -246,20 +257,9 @@ impl Ray {
         match bvh {
             Some(bvh) => {
                 //We have a bvh so use bvh traversal
-                for (_, node) in &scene.nodes {
-                    if !node.active {
-                        continue;
-                    }
-                    match bvh.traverse(self, 0) {
-                        Some((_, intersect)) => {
-                            if intersect.distance < light_distance {
-                                return true;
-                            }
-                        }
-                        None => continue,
-                    }
+                if let Some((_, intersect)) = bvh.traverse(self, 0) {
+                    return intersect.distance < light_distance;
                 }
-                return false;
             }
             None => {
                 for (_, node) in &scene.nodes {

src/state.rs

@@ -5,6 +5,7 @@ use crate::camera::Camera;
 use crate::ray::Ray;
 use crate::{gui::Gui, scene::Scene};
 use crate::{gui::GuiEvent, log_error};
+use std::collections::HashSet;
 use std::path::Path;
 use std::thread;
 
@@ -13,12 +14,15 @@ use rand::seq::SliceRandom;
 use rand::{random, thread_rng};
 
 use std::error::Error;
-use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{mpsc, Arc, Mutex};
 
 use anyhow::Result;
 use pixels::{Pixels, SurfaceTexture};
 use winit::dpi::{LogicalSize, PhysicalSize};
-use winit::event::{Event, KeyboardInput, MouseButton, VirtualKeyCode, WindowEvent};
+use winit::event::{
+    ElementState, Event, KeyboardInput, MouseButton, VirtualKeyCode, WindowEvent,
+};
 use winit::event_loop::{ControlFlow, EventLoop};
 use winit::window::{Window, WindowBuilder};
 
@@ -72,6 +76,9 @@ impl RaytracingOption {
     }
 }
 
+const CAMERA_MOVE_SPEED: f64 = 0.15;
+const CAMERA_ORBIT_SPEED: f64 = 0.005;
+
 pub struct State {
     scene: Arc<Scene>,
     bvh: Arc<Option<BVH>>,
@@ -85,8 +92,17 @@ pub struct State {
     gui: Gui,
 
     rays: Arc<Vec<Ray>>,
-    ray_queue: Vec<usize>,
+    ray_queue: Arc<Mutex<Vec<usize>>>,
     raytracing_options: Arc<RaytracingOption>,
+
+    result_rx: mpsc::Receiver<Vec<(usize, [u8; 4])>>,
+    render_active: Arc<AtomicBool>,
+    rendering: bool,
+
+    keys_pressed: HashSet<VirtualKeyCode>,
+    right_mouse_down: bool,
+    last_mouse_pos: Option<(f64, f64)>,
+    camera_dirty: bool,
 }
 
 impl State {
@@ -96,6 +112,7 @@ impl State {
         let pixels = pixels;
         let camera = Camera::unit();
         let rays = Arc::new(Vec::new());
+        let (_tx, rx) = mpsc::channel();
 
         Self {
             scene,
@@ -107,8 +124,15 @@ impl State {
             pixels,
             gui,
             rays,
-            ray_queue: Vec::new(),
+            ray_queue: Arc::new(Mutex::new(Vec::new())),
             raytracing_options: Arc::new(RaytracingOption::default()),
+            result_rx: rx,
+            render_active: Arc::new(AtomicBool::new(false)),
+            rendering: false,
+            keys_pressed: HashSet::new(),
+            right_mouse_down: false,
+            last_mouse_pos: None,
+            camera_dirty: false,
         }
     }
 
@@ -192,98 +216,109 @@ impl State {
     }
 
     fn keyboard_input(&mut self, key: &KeyboardInput) {
-        if let Some(VirtualKeyCode::A) = key.virtual_keycode {
-            // Handle 'A' key event here
-        }
-    }
-
-    fn mouse_input(&mut self, _button: &MouseButton) {
-        // Handle mouse input here
-    }
-
-    fn draw(&mut self) -> Result<(), Box<dyn Error>> {
-        //Draw ray_num in a block
-        let randomness = self.raytracing_options.ray_randomness;
-        let samples = self.raytracing_options.ray_samples;
-        let samples_f32 = samples as f32;
-
-        let num_threads = self.raytracing_options.threads;
-        let pixels_per_thread = self.raytracing_options.pixels_per_thread;
-
-        let mut handles = vec![];
-
-        for _ in 0..num_threads {
-            //Get necessary variables to render
-            let rays = self.rays.clone();
-            let scene = self.scene.clone();
-            let options = self.raytracing_options.clone();
-            let bvh = self.bvh.clone();
-
-            //Get the workload for a thread
-            let mut load = vec![];
-            for _ in 0..pixels_per_thread {
-                match self.ray_queue.pop() {
-                    Some(index) => load.push(index),
-                    None => break,
+        if let Some(keycode) = key.virtual_keycode {
+            match key.state {
+                ElementState::Pressed => {
+                    self.keys_pressed.insert(keycode);
+                }
+                ElementState::Released => {
+                    self.keys_pressed.remove(&keycode);
                 }
             }
-            //The finished queue of the thread
-            let mut finished = vec![];
+        }
+    }
 
-            //Create a new thread for these pixels
-            let handle = thread::spawn({
-                move || {
-                    for index in &load {
-                        //Shade colour for selected index
-                        let mut colour: Vector3<f32> = Vector3::zeros();
-                        let ray = &rays[*index];
-                        for _ in 0..samples {
-                            //Generate a ray in a random direction
-                            let point = ray.a;
-                            let dir = ray.b;
-                            let rx = (random::<f64>() - 0.5) / randomness;
-                            let ry = (random::<f64>() - 0.5) / randomness;
-                            let rz = (random::<f64>() - 0.5) / randomness;
-                            let nx = dir.x + rx;
-                            let ny = dir.y + ry;
-                            let nz = dir.z + rz;
+    fn mouse_input(&mut self, button: &MouseButton, state: &ElementState) {
+        if *button == MouseButton::Right {
+            self.right_mouse_down = *state == ElementState::Pressed;
+            if !self.right_mouse_down {
+                self.last_mouse_pos = None;
+            }
+        }
+    }
 
-                            let rand_ray = Ray::new(point, Vector3::new(nx, ny, nz));
+    fn cursor_moved(&mut self, x: f64, y: f64) {
+        if self.right_mouse_down {
+            if let Some((last_x, last_y)) = self.last_mouse_pos {
+                let dx = x - last_x;
+                let dy = y - last_y;
+                self.camera.orbit(
+                    -dx * CAMERA_ORBIT_SPEED,
+                    -dy * CAMERA_ORBIT_SPEED,
+                );
+                self.camera_dirty = true;
+            }
+            self.last_mouse_pos = Some((x, y));
+        }
+    }
 
-                            if let Some(ray_colour) = rand_ray.shade_ray(&scene, 0, &options, &bvh)
-                            {
-                                colour += ray_colour;
-                            }
-                        }
-                        colour = (colour / samples_f32) * 255.0;
-                        let rgba = [colour.x as u8, colour.y as u8, colour.z as u8, 0xff];
-                        finished.push(rgba);
+    fn process_camera_movement(&mut self) {
+        let speed = CAMERA_MOVE_SPEED;
+
+        if self.keys_pressed.contains(&VirtualKeyCode::W) {
+            self.camera.move_forward(speed);
+            self.camera_dirty = true;
+        }
+        if self.keys_pressed.contains(&VirtualKeyCode::S) {
+            self.camera.move_forward(-speed);
+            self.camera_dirty = true;
+        }
+        if self.keys_pressed.contains(&VirtualKeyCode::A) {
+            self.camera.move_right(-speed);
+            self.camera_dirty = true;
+        }
+        if self.keys_pressed.contains(&VirtualKeyCode::D) {
+            self.camera.move_right(speed);
+            self.camera_dirty = true;
+        }
+        if self.keys_pressed.contains(&VirtualKeyCode::Q) {
+            self.camera.move_up(-speed);
+            self.camera_dirty = true;
+        }
+        if self.keys_pressed.contains(&VirtualKeyCode::E) {
+            self.camera.move_up(speed);
+            self.camera_dirty = true;
+        }
+
+        if self.camera_dirty {
+            self.camera_dirty = false;
+            self.rays = Arc::new(Ray::cast_rays(
+                &self.camera.eye,
+                &self.camera.target,
+                &self.camera.up,
+                self.raytracing_options.buffer_fov,
+                self.buffer_width,
+                self.buffer_height,
+            ));
+            self.gui.update_camera(&self.camera);
+            let _ = self.clear_buffer();
+            self.reset_queue();
+        }
+    }
+
+    fn draw(&mut self) {
+        if !self.rendering {
+            return;
+        }
+
+        // Drain completed results from background workers
+        loop {
+            match self.result_rx.try_recv() {
+                Ok(results) => {
+                    let frame = self.pixels.frame_mut();
+                    for (index, rgba) in results {
+                        frame[index * 4..(index + 1) * 4].copy_from_slice(&rgba);
                     }
-                    return (load, finished);
                 }
-            });
-            handles.push(handle);
+                Err(mpsc::TryRecvError::Empty) => break,
+                Err(mpsc::TryRecvError::Disconnected) => {
+                    // All worker threads have finished
+                    self.rendering = false;
+                    self.gui.stop_render_timer();
+                    break;
+                }
+            }
         }
-
-        let mut all_results = vec![];
-
-        for handle in handles.drain(..) {
-            let (load, finished) = handle
-                .join()
-                .map_err(|e| format!("Thread panicked: {:?}", e))?;
-            let thread_results: Vec<_> = load.into_iter().zip(finished.into_iter()).collect();
-            all_results.extend(thread_results);
-        }
-
-        //Now we have two vectors will all the indicies and rgba values, we can upload them to the bufer
-
-        let frame = self.pixels.frame_mut();
-        for result in all_results {
-            let index = result.0;
-            let rgba = result.1;
-            frame[index * 4..(index + 1) * 4].copy_from_slice(&rgba);
-        }
-        Ok(())
     }
 
     fn clear_buffer(&mut self) -> Result<(), Box<dyn Error>> {
@@ -295,26 +330,113 @@ impl State {
     }
 
     fn reset_queue(&mut self) {
+        // Signal any existing workers to stop
+        self.render_active.store(false, Ordering::Relaxed);
+
         match self.raytracing_options.bvh_active {
             true => self.bvh = Arc::new(Some(BVH::build(&self.scene.nodes))),
             false => self.bvh = Arc::new(None),
         }
+
+        // Create new shuffled queue
         let size = self.buffer_height as usize * self.buffer_width as usize;
         let mut ray_queue: Vec<usize> = (0..size).collect();
         ray_queue.shuffle(&mut thread_rng());
-        self.ray_queue = ray_queue;
+        self.ray_queue = Arc::new(Mutex::new(ray_queue));
+
+        // Create new channel and active flag
+        let (tx, rx) = mpsc::channel();
+        self.result_rx = rx;
+        let render_active = Arc::new(AtomicBool::new(true));
+        self.render_active = render_active.clone();
+        self.rendering = true;
+
+        // Spawn persistent worker threads
+        let num_threads = self.raytracing_options.threads;
+        let pixels_per_thread = self.raytracing_options.pixels_per_thread;
+
+        for _ in 0..num_threads {
+            let rays = self.rays.clone();
+            let scene = self.scene.clone();
+            let options = self.raytracing_options.clone();
+            let bvh = self.bvh.clone();
+            let queue = self.ray_queue.clone();
+            let tx = tx.clone();
+            let active = render_active.clone();
+
+            thread::spawn(move || {
+                let randomness = options.ray_randomness;
+                let samples = options.ray_samples;
+                let samples_f32 = samples as f32;
+
+                loop {
+                    if !active.load(Ordering::Relaxed) {
+                        break;
+                    }
+
+                    // Pop a batch from the shared queue
+                    let load: Vec<usize> = {
+                        let mut q = queue.lock().unwrap();
+                        let mut batch = Vec::with_capacity(pixels_per_thread as usize);
+                        for _ in 0..pixels_per_thread {
+                            match q.pop() {
+                                Some(index) => batch.push(index),
+                                None => break,
+                            }
+                        }
+                        batch
+                    };
+
+                    if load.is_empty() {
+                        break;
+                    }
+
+                    // Process the batch
+                    let mut results = Vec::with_capacity(load.len());
+                    for index in &load {
+                        let mut colour: Vector3<f32> = Vector3::zeros();
+                        let ray = &rays[*index];
+                        for _ in 0..samples {
+                            let point = ray.a;
+                            let dir = ray.b;
+                            let rx = (random::<f64>() - 0.5) / randomness;
+                            let ry = (random::<f64>() - 0.5) / randomness;
+                            let rz = (random::<f64>() - 0.5) / randomness;
+                            let nx = dir.x + rx;
+                            let ny = dir.y + ry;
+                            let nz = dir.z + rz;
+
+                            let rand_ray = Ray::new(point, Vector3::new(nx, ny, nz));
+
+                            if let Some(ray_colour) =
+                                rand_ray.shade_ray(&scene, 0, &options, &bvh)
+                            {
+                                colour += ray_colour;
+                            }
+                        }
+                        colour = (colour / samples_f32) * 255.0;
+                        let rgba = [colour.x as u8, colour.y as u8, colour.z as u8, 0xff];
+                        results.push((*index, rgba));
+                    }
+
+                    // Send results back to main thread
+                    if tx.send(results).is_err() {
+                        break;
+                    }
+                }
+            });
+        }
+        // Drop our copy of tx so the channel disconnects when all workers finish
+        drop(tx);
+
+        self.gui.start_render_timer();
     }
 
     fn render(&mut self) -> Result<(), Box<dyn Error>> {
         // Update state
         self.update()?;
-        // Draw rays if we have remaining rays in queue
-        match self.draw() {
-            Err(e) => {
-                println!("ERROR: {}", e);
-            }
-            _ => {}
-        }
+        // Collect completed rays from background workers
+        self.draw();
         // Render Gui
         self.gui
             .prepare(&self.window)
@@ -355,11 +477,17 @@ pub fn run() -> Result<(), Box<dyn Error>> {
                 WindowEvent::CloseRequested => *control_flow = ControlFlow::Exit,
                 WindowEvent::Resized(size) => state.resize(&size).expect("Window Resize Error"),
                 WindowEvent::KeyboardInput { input, .. } => state.keyboard_input(&input),
-                WindowEvent::MouseInput { button, .. } => state.mouse_input(&button),
+                WindowEvent::MouseInput { button, state: elem_state, .. } => {
+                    state.mouse_input(&button, &elem_state)
+                }
+                WindowEvent::CursorMoved { position, .. } => {
+                    state.cursor_moved(position.x, position.y)
+                }
                 _ => {}
             },
 
             Event::RedrawRequested(_) => {
+                state.process_camera_movement();
                 if let Err(_e) = state.render() {
                     *control_flow = ControlFlow::Exit;
                 }