add particle sim (#13)

* Add the ability to add a compute pass

* Add particles gameobject (does nothing yet)

* feat: Add particle system with WebGPU rendering and basic movement

* refactor: Update particle rendering and shader structure

* Rendering one particle!!

* feat: Add DrawInstanced method to RenderPass for instanced rendering support

* refactor: Implement Draw using DrawInstanced with single instance

* feat: Add parent pointer to GameObject and set parent references in get_gameobjects

* refactor: Implement recursive game object traversal with proper parent handling

* Reorder

* refactor: Split CalculateMVP into separate model, view, and projection functions

* feat: Add MVP() method to GameObject for easy matrix calculation

* feat: Add parent transform inheritance to GameObject MVP calculation

* use MVP

* feat: Add VertexBufferLayouts template for composing multiple vertex buffer layouts

* refactor: Update RenderPipeline to support multiple vertex buffer layouts

* tweak

* refactor: Fix VertexBufferLayouts to handle move-only VertexBufferInfo

* hmm

* Instancing works!

* confetti!!

* Initial compute shader

* refactor: Update BindGroupLayout to include buffer count in getId and setEntry methods

* fix: Resolve type conversion and narrowing issues in BindGroupLayout

* feat: Add WorldInfo struct to pass deltaTime and mouse position to compute shader

* feat: Add worldInfo uniform buffer to Particles constructor

* feat: Add gravitational mouse attraction to particle simulation

* play with gravity

* increase workgroup size

* feat: Add SceneGeometry class for managing 3D scene geometry

* refactor: Extract scene geometry computation to SceneGeometry class

* refactor: Split computeSceneGeometry into separate wall and invisibility path functions

* refactor: Inline getFlattenedBounds and computeInvisibilityPaths methods

* simplify

* refactor: Simplify visibility computation method signature

* feat: Add BVH acceleration structure for line intersection tests in wall paths

* fix: Remove duplicate AABB constructor and improve comments

* feat: Add line intersection method to BVHNode for efficient line segment intersection checks

* refactor: Move BVH implementation to separate source file

* feat: Add ray intersection method to BVH for efficient ray-segment intersection

* refactor: Remove unused `cull_frontfaces` flag in visibility polygon computation

* refactor: Modify visibility polygon computation to use BVH acceleration structure

* Use BVH acceleration structure when computing FoW

* feat: Add BVH debug visualization with recursive AABB drawing

* Flattenable-BVH

* feat: Add shader include processing functionality

* Rearrange

* More compact BVHNode

* weird

* Can't believe that was it

* bring force back

* refactor: Add normal to SegmentIntersection struct for improved ray tracing

* feat: Implement realistic particle wall bouncing with reflection physics

* update buffer

* only spawn particles when p is pressed

* buffer upload resize should be based on capacity

* push rather than emplace

* hmm

Author: anchpop

.gitignore

@@ -405,3 +405,7 @@ res_path.hpp
 
 build_emscripten
 build_analysis
+.aider*
+.env
+
+build_xcode

.vscode/settings.json

@@ -89,7 +89,10 @@
         "print": "cpp",
         "filesystem": "cpp",
         "forward_list": "cpp",
-        "ranges": "cpp"
+        "ranges": "cpp",
+        "cfenv": "cpp",
+        "regex": "cpp",
+        "valarray": "cpp"
     },
     "files.exclude": {
         "build": true,

OpenGL/res/shaders/particles.wgsl

@@ -0,0 +1,46 @@
+struct Particle {
+    @location(1) position: vec2<f32>,  // World space position
+    @location(2) velocity: vec2<f32>,
+    @location(3) color: vec4<f32>,
+};
+
+struct VertexInput {
+    @location(0) position: vec2<f32>,  // Local vertex position (relative to particle center)
+};
+
+// Separate matrices for clearer transform chain
+struct VertexUniforms {
+    world_to_clip: mat4x4<f32>,    // View-Projection matrix only
+};
+
+@group(0) @binding(0)
+var<uniform> vertexUniforms: VertexUniforms;
+
+struct VertexOutput {
+    @builtin(position) Position: vec4<f32>,
+    @location(0) color: vec4<f32>,
+};
+
+struct FragmentOutput {
+    @location(0) color: vec4<f32>,
+};
+
+@vertex
+fn vertex_main(vertex: VertexInput, particle: Particle) -> VertexOutput {
+    var output: VertexOutput;
+    
+    // Transform the local vertex position to world space relative to particle position
+    let world_pos = vertex.position + particle.position;
+    
+    // Transform from world space to clip space using world_to_clip matrix
+    output.Position = vertexUniforms.world_to_clip * vec4<f32>(world_pos, 0.0, 1.0);
+    output.color = particle.color;
+    return output;
+}
+
+@fragment
+fn fragment_main(input: VertexOutput) -> FragmentOutput {
+    var output: FragmentOutput;
+    output.color = input.color;
+    return output;
+}

OpenGL/res/shaders/particlesCompute.wgsl

@@ -0,0 +1,209 @@
+struct WorldInfo {
+    deltaTime : f32,
+    mousePos  : vec2<f32>,
+};
+
+struct Particle {
+    position : vec2<f32>,  // World space position
+    velocity : vec2<f32>,
+    color    : vec4<f32>,
+};
+
+struct Segment {
+    start : vec2<f32>,
+    end   : vec2<f32>,
+};
+
+struct BvhNode {
+    leftTypeCount : u32,    // leftType :1, leftCount :31
+    leftOffset    : u32,
+
+    rightTypeCount : u32,   // rightType :1, rightCount :31
+    rightOffset    : u32,
+
+    leftBBoxMin  : vec2<f32>,
+    leftBBoxMax  : vec2<f32>,
+
+    rightBBoxMin : vec2<f32>,
+    rightBBoxMax : vec2<f32>,
+};
+
+struct AABB {
+    min : vec2<f32>,
+    max : vec2<f32>,
+};
+
+// Helper functions to unpack BVH Node data
+fn getLeftType(node : BvhNode) -> u32 {
+    return node.leftTypeCount >> 31u;
+}
+
+fn getLeftCount(node : BvhNode) -> u32 {
+    return node.leftTypeCount & 0x7FFFFFFFu;
+}
+
+fn getRightType(node : BvhNode) -> u32 {
+    return node.rightTypeCount >> 31u;
+}
+
+fn getRightCount(node : BvhNode) -> u32 {
+    return node.rightTypeCount & 0x7FFFFFFFu;
+}
+
+fn isLeafNode(node : BvhNode, isLeft : bool) -> bool {
+    if isLeft {
+        return getLeftType(node) == 1u;
+    } else {
+        return getRightType(node) == 1u;
+    }
+}
+
+fn getChildOffset(node : BvhNode, isLeft : bool) -> u32 {
+    if isLeft {
+        return node.leftOffset;
+    } else {
+        return node.rightOffset;
+    }
+}
+
+fn getChildCount(node : BvhNode, isLeft : bool) -> u32 {
+    if isLeft {
+        return getLeftCount(node);
+    } else {
+        return getRightCount(node);
+    }
+}
+
+fn getChildBBox(node : BvhNode, isLeft : bool) -> AABB {
+    if isLeft {
+        return AABB(node.leftBBoxMin, node.leftBBoxMax);
+    } else {
+        return AABB(node.rightBBoxMin, node.rightBBoxMax);
+    }
+}
+
+// Utility functions
+fn cross2D(a : vec2<f32>, b : vec2<f32>) -> f32 {
+    return a.x * b.y - a.y * b.x;
+}
+
+fn dot2D(a : vec2<f32>, b : vec2<f32>) -> f32 {
+    return a.x * b.x + a.y * b.y;
+}
+
+struct Ray {
+    origin    : vec2<f32>,
+    direction : vec2<f32>,
+};
+
+struct SegmentIntersection {
+    hit      : bool,
+    position : vec2<f32>,
+    normal   : vec2<f32>,
+    t        : f32,
+};
+
+// Buffer bindings
+@group(0) @binding(0) var<storage, read_write> particleBuffer : array<Particle>;
+@group(0) @binding(1) var<uniform> world : WorldInfo;
+@group(0) @binding(2) var<storage, read> segments : array<Segment>;
+@group(0) @binding(3) var<storage, read> bvhNodes : array<BvhNode>;
+
+// Constants
+const G : f32 = 30.0; 
+const MIN_DISTANCE_SQUARED : f32 = 1.0; // Prevent division by zero
+
+// Compute shader entry point
+@compute @workgroup_size(256)
+fn compute_main(@builtin(global_invocation_id) id : vec3<u32>) {
+    let index = id.x;
+
+    let particle = &particleBuffer[index];
+
+    // Calculate direction to mouse
+    let toMouse = world.mousePos - particle.position;
+    let distanceSquared = max(dot2D(toMouse, toMouse), MIN_DISTANCE_SQUARED);
+
+    // Calculate gravitational force (F = G * m1 * m2 / r^2)
+    // Since mass is uniform we can simplify
+    let force = normalize(toMouse) * G / distanceSquared;
+
+    // Update velocity (a = F/m, simplified since mass = 1)
+    particleBuffer[index].velocity += force * world.deltaTime;
+
+    // New position based on velocity
+    let newPosition = particle.position + particleBuffer[index].velocity * world.deltaTime;
+
+    // Check for collision with walls
+    let intersection = findWallCollision(particle.position, newPosition);
+    
+    if (intersection.hit) {
+        // Bounce coefficient (1.0 = perfect bounce, 0.0 = full stop)
+        let bounce = 0.8;
+        
+        // Calculate reflection vector
+        let v = particleBuffer[index].velocity;
+        let n = intersection.normal;
+        let reflected = v - 2.0 * dot2D(v, n) * n;
+        
+        // Update velocity with bounce effect
+        let newVelocity = reflected * bounce;
+        particleBuffer[index].velocity = newVelocity;
+        
+        // Place particle at intersection point
+        particleBuffer[index].position = intersection.position + newVelocity * world.deltaTime;
+    } else {
+        // No collision, update particle position normally
+        particleBuffer[index].position = newPosition;
+    }
+}
+
+fn findWallCollision(particlePosition : vec2<f32>, newPosition : vec2<f32>) -> SegmentIntersection {
+    var closest : SegmentIntersection;
+    closest.hit = false;
+    closest.t = 999999.0;
+
+    let particlePath = Segment(particlePosition, newPosition);
+    
+    for (var i: u32 = 0; i < arrayLength(&segments); i++) {
+        let wall = segments[i];
+        let intersection = segmentIntersection(wall, particlePath);
+        
+        if (intersection.hit && intersection.t < closest.t) {
+            closest = intersection;
+        }
+    }
+    
+    return closest;
+}
+
+fn segmentIntersection(s1 : Segment, s2 : Segment) -> SegmentIntersection {
+    var result : SegmentIntersection;
+    result.hit = false;
+    
+    let p = s1.start;
+    let r = s1.end - s1.start;
+    let q = s2.start;
+    let s = s2.end - s2.start;
+
+    let r_cross_s = cross2D(r, s);
+    let q_p = q - p;
+
+    if (abs(r_cross_s) < 1e-8) {
+        return result; // Lines are parallel
+    }
+
+    let t = cross2D(q_p, s) / r_cross_s;
+    let u = cross2D(q_p, r) / r_cross_s;
+
+    if (t >= 0.0 && t <= 1.0 && u >= 0.0 && u <= 1.0) {
+        result.hit = true;
+        result.t = t;
+        result.position = p + t * r;
+        result.normal = normalize(vec2<f32>(-r.y, r.x)); // Perpendicular to wall
+        return result;
+    }
+
+    return result;
+}
+

OpenGL/res/shaders/stars.wgsl

@@ -116,7 +116,7 @@ fn starColor(seed: f32) -> vec3<f32> {
 fn main_1() {
     var uv_2: vec2<f32>;
     var aspectRatio: f32;
-    var numStars: i32 = 502i;
+    var numStars: i32 = 2i;
     var finalColor: vec3<f32> = vec3(0f);
     var i: i32 = 0i;
     var seed_2: f32;