render: implement packed texture atlas for shadow maps

Cargo.lock

@@ -1881,6 +1881,7 @@ dependencies = [
  "lyra-scene",
  "petgraph",
  "quote",
+ "rectangle-pack",
  "rustc-hash",
  "syn 2.0.51",
  "thiserror",
@@ -2767,6 +2768,12 @@ dependencies = [
  "rand_core 0.3.1",
 ]
 
+[[package]]
+name = "rectangle-pack"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0d463f2884048e7153449a55166f91028d5b0ea53c79377099ce4e8cf0cf9bb"
+
 [[package]]
 name = "redox_syscall"
 version = "0.3.5"

lyra-game/Cargo.toml

@@ -38,6 +38,7 @@ unique = "0.9.1"
 rustc-hash = "1.1.0"
 petgraph = { version = "0.6.5", features = ["matrix_graph"] }
 bind_match = "0.1.2"
+rectangle-pack = "0.4.2"
 
 [features]
 tracy = ["dep:tracing-tracy"]

lyra-game/src/render/graph/passes/meshes.rs

@@ -116,9 +116,14 @@ impl Node for MeshPass {
                 .expect("missing ShadowMapsPassSlots::ShadowAtlasSampler")
                 .as_sampler()
                 .unwrap();
-            let dir_light_projection_buf = graph
+            let atlas_size_buf = graph
-                .slot_value(ShadowMapsPassSlots::DirLightProjectionBuffer)
+                .slot_value(ShadowMapsPassSlots::ShadowAtlasSizeBuffer)
-                .expect("missing ShadowMapsPassSlots::DirLightProjectionBuffer")
+                .expect("missing ShadowMapsPassSlots::ShadowAtlasSizeBuffer")
+                .as_buffer()
+                .unwrap();
+            let light_uniform_buf = graph
+                .slot_value(ShadowMapsPassSlots::ShadowLightUniformsBuffer)
+                .expect("missing ShadowMapsPassSlots::ShadowLightUniformsBuffer")
                 .as_buffer()
                 .unwrap();
 
@@ -151,6 +156,16 @@ impl Node for MeshPass {
                         },
                         count: None,
                     },
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 3,
+                        visibility: wgpu::ShaderStages::VERTEX_FRAGMENT,
+                        ty: wgpu::BindingType::Buffer {
+                            ty: wgpu::BufferBindingType::Uniform,
+                            has_dynamic_offset: false,
+                            min_binding_size: None,
+                        },
+                        count: None,
+                    },
                 ],
             });
 
@@ -169,7 +184,15 @@ impl Node for MeshPass {
                     wgpu::BindGroupEntry {
                         binding: 2,
                         resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
-                            buffer: dir_light_projection_buf,
+                            buffer: atlas_size_buf,
+                            offset: 0,
+                            size: None,
+                        }),
+                    },
+                    wgpu::BindGroupEntry {
+                        binding: 3,
+                        resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
+                            buffer: light_uniform_buf,
                             offset: 0,
                             size: None,
                         }),

lyra-game/src/render/graph/passes/shadows.rs

@@ -1,9 +1,7 @@
-use std::{mem, num::NonZeroU64, rc::Rc, sync::Arc};
+use std::{collections::VecDeque, mem, num::NonZeroU64, ops::Deref, rc::Rc, sync::{Arc, RwLock, RwLockReadGuard, RwLockWriteGuard}};
 
-use glam::UVec2;
 use lyra_ecs::{
-    query::{filter::Has, Entities},
+    query::{filter::Has, Entities}, AtomicRef, Component, Entity, ResourceData
-    AtomicRef, Entity, ResourceData,
 };
 use lyra_game_derive::RenderGraphLabel;
 use lyra_math::Transform;
@@ -12,24 +10,20 @@ use tracing::{debug, warn};
 use wgpu::util::DeviceExt;
 
 use crate::render::{
-    graph::{Node, NodeDesc, NodeType, SlotAttribute, SlotValue},
+    graph::{Node, NodeDesc, NodeType, SlotAttribute, SlotValue}, light::directional::DirectionalLight, resource::{RenderPipeline, RenderPipelineDescriptor, Shader, VertexState}, transform_buffer_storage::TransformBuffers, vertex::Vertex, AtlasViewport, TextureAtlas
-    light::directional::DirectionalLight,
-    resource::{RenderPipeline, RenderPipelineDescriptor, Shader, VertexState},
-    transform_buffer_storage::TransformBuffers,
-    vertex::Vertex,
-    TextureAtlas,
 };
 
 use super::{MeshBufferStorage, RenderAssets, RenderMeshes};
 
-const SHADOW_SIZE: glam::UVec2 = glam::UVec2::new(1024, 1024);
+const SHADOW_SIZE: glam::UVec2 = glam::uvec2(1024, 1024);
 
 #[derive(Debug, Clone, Hash, PartialEq, RenderGraphLabel)]
 pub enum ShadowMapsPassSlots {
     ShadowAtlasTexture,
     ShadowAtlasTextureView,
     ShadowAtlasSampler,
-    DirLightProjectionBuffer,
+    ShadowAtlasSizeBuffer,
+    ShadowLightUniformsBuffer,
 }
 
 #[derive(Debug, Clone, Hash, PartialEq, RenderGraphLabel)]
@@ -38,10 +32,12 @@ pub struct ShadowMapsPassLabel;
 struct LightDepthMap {
     light_projection_buffer: Arc<wgpu::Buffer>,
     bindgroup: wgpu::BindGroup,
+    atlas_index: u64,
 }
 
 pub struct ShadowMapsPass {
     bgl: Arc<wgpu::BindGroupLayout>,
+    atlas_size_buffer: Arc<wgpu::Buffer>,
     /// depth maps for a light owned by an entity.
     depth_maps: FxHashMap<Entity, LightDepthMap>,
 
@@ -52,7 +48,7 @@ pub struct ShadowMapsPass {
     mesh_buffers: Option<ResourceData>,
     pipeline: Option<RenderPipeline>,
 
-    atlas: Arc<TextureAtlas>,
+    atlas: LightShadowMapAtlas,
     /// The depth map atlas sampler
     atlas_sampler: Rc<wgpu::Sampler>,
 }
@@ -61,50 +57,38 @@ impl ShadowMapsPass {
     pub fn new(device: &wgpu::Device) -> Self {
         let bgl = Arc::new(
             device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
-                label: Some("bgl_shadows_light_projection"),
+                label: Some("bgl_shadow_maps_lights"),
-                entries: &[wgpu::BindGroupLayoutEntry {
+                entries: &[
-                    binding: 0,
+                    wgpu::BindGroupLayoutEntry {
-                    visibility: wgpu::ShaderStages::VERTEX,
+                        binding: 0,
-                    ty: wgpu::BindingType::Buffer {
+                        visibility: wgpu::ShaderStages::VERTEX_FRAGMENT,
-                        ty: wgpu::BufferBindingType::Uniform,
+                        ty: wgpu::BindingType::Buffer {
-                        has_dynamic_offset: false,
+                            ty: wgpu::BufferBindingType::Uniform,
-                        min_binding_size: Some(
+                            has_dynamic_offset: false,
-                            NonZeroU64::new(mem::size_of::<glam::Mat4>() as _).unwrap(),
+                            min_binding_size: Some(
-                        ),
+                                NonZeroU64::new(mem::size_of::<LightShadowUniform>() as _).unwrap(),
-                    },
+                            ),
-                    count: None,
+                        },
-                }],
+                        count: None,
+                    }
+                ],
             }),
         );
 
-        /* let tex = device.create_texture(&wgpu::TextureDescriptor {
-            label: Some("texture_shadow_map_atlas"),
-            size: wgpu::Extent3d {
-                width: SHADOW_SIZE.x,
-                height: SHADOW_SIZE.y,
-                depth_or_array_layers: 1,
-            },
-            mip_level_count: 1,
-            sample_count: 1,
-            dimension: wgpu::TextureDimension::D2,
-            format: wgpu::TextureFormat::Depth32Float,
-            usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::TEXTURE_BINDING,
-            view_formats: &[],
-        });
-
-        let view = tex.create_view(&wgpu::TextureViewDescriptor {
-            label: Some("shadows_map_view"),
-            ..Default::default()
-        }); */
-
         let atlas = TextureAtlas::new(
             device,
             wgpu::TextureFormat::Depth32Float,
             wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::TEXTURE_BINDING,
-            SHADOW_SIZE,
+            SHADOW_SIZE * 4,
-            UVec2::new(4, 4),
         );
 
+        let atlas_size_buffer =
+            device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+                label: Some("buffer_shadow_maps_atlas_size"),
+                usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+                contents: bytemuck::bytes_of(&atlas.atlas_size()),
+            });
+
         let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
             label: Some("sampler_shadow_map_atlas"),
             address_mode_u: wgpu::AddressMode::ClampToBorder,
@@ -119,6 +103,7 @@ impl ShadowMapsPass {
 
         Self {
             bgl,
+            atlas_size_buffer: Arc::new(atlas_size_buffer),
             depth_maps: Default::default(),
             transform_buffers: None,
             render_meshes: None,
@@ -126,14 +111,20 @@ impl ShadowMapsPass {
             pipeline: None,
 
             atlas_sampler: Rc::new(sampler),
-            atlas: Arc::new(atlas),
+            atlas: LightShadowMapAtlas(Arc::new(RwLock::new(atlas))),
         }
     }
 
-    fn create_depth_map(&mut self, device: &wgpu::Device, entity: Entity, light_pos: Transform) {
+    /// Create a depth map and return the id of the depth map in the texture atlas.
+    fn create_depth_map(&mut self, device: &wgpu::Device, entity: Entity, light_pos: Transform) -> u64 {
         const NEAR_PLANE: f32 = 0.1;
         const FAR_PLANE: f32 = 45.0;
 
+        let mut atlas = self.atlas.get_mut();
+        let atlas_index = atlas.pack_new_texture(SHADOW_SIZE.x as _, SHADOW_SIZE.y as _)
+            .expect("failed to pack new shadow map into texture atlas");
+        let atlas_frame = atlas.texture_viewport(atlas_index);
+
         let ortho_proj =
             glam::Mat4::orthographic_rh(-10.0, 10.0, -10.0, 10.0, NEAR_PLANE, FAR_PLANE);
 
@@ -141,25 +132,31 @@ impl ShadowMapsPass {
             glam::Mat4::look_to_rh(light_pos.translation, light_pos.forward(), light_pos.up());
 
         let light_proj = ortho_proj * look_view;
+        let uniform = LightShadowUniform {
+            space_mat: light_proj,
+            atlas_frame,
+        };
 
         let light_projection_buffer =
             device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
-                label: Some("shadows_light_view_mat_buffer"),
+                label: Some("buffer_shadow_maps_light"),
                 usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
-                contents: bytemuck::bytes_of(&light_proj),
+                contents: bytemuck::bytes_of(&uniform),
             });
 
         let bg = device.create_bind_group(&wgpu::BindGroupDescriptor {
-            label: Some("shadows_bind_group"),
+            label: Some("shadow_maps_bind_group"),
             layout: &self.bgl,
-            entries: &[wgpu::BindGroupEntry {
+            entries: &[
-                binding: 0,
+                wgpu::BindGroupEntry {
-                resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
+                    binding: 0,
-                    buffer: &light_projection_buffer,
+                    resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
-                    offset: 0,
+                        buffer: &light_projection_buffer,
-                    size: None,
+                        offset: 0,
-                }),
+                        size: None,
-            }],
+                    }),
+                }
+            ],
         });
 
         self.depth_maps.insert(
@@ -167,8 +164,11 @@ impl ShadowMapsPass {
             LightDepthMap {
                 light_projection_buffer: Arc::new(light_projection_buffer),
                 bindgroup: bg,
+                atlas_index
             },
         );
+
+        atlas_index
     }
 
     fn transform_buffers(&self) -> AtomicRef<TransformBuffers> {
@@ -191,16 +191,18 @@ impl Node for ShadowMapsPass {
     ) -> crate::render::graph::NodeDesc {
         let mut node = NodeDesc::new(NodeType::Render, None, vec![]);
 
+        let atlas = self.atlas.get();
+
         node.add_texture_slot(
             ShadowMapsPassSlots::ShadowAtlasTexture,
             SlotAttribute::Output,
-            Some(SlotValue::Texture(self.atlas.texture().clone())),
+            Some(SlotValue::Texture(atlas.texture().clone())),
         );
 
         node.add_texture_view_slot(
             ShadowMapsPassSlots::ShadowAtlasTextureView,
             SlotAttribute::Output,
-            Some(SlotValue::TextureView(self.atlas.view().clone())),
+            Some(SlotValue::TextureView(atlas.view().clone())),
         );
 
         node.add_sampler_slot(
@@ -210,11 +212,17 @@ impl Node for ShadowMapsPass {
         );
 
         node.add_sampler_slot(
-            ShadowMapsPassSlots::DirLightProjectionBuffer,
+            ShadowMapsPassSlots::ShadowLightUniformsBuffer,
             SlotAttribute::Output,
             Some(SlotValue::Lazy),
         );
 
+        node.add_buffer_slot(
+            ShadowMapsPassSlots::ShadowAtlasSizeBuffer,
+            SlotAttribute::Output,
+            Some(SlotValue::Buffer(self.atlas_size_buffer.clone())),
+        );
+
         node
     }
 
@@ -230,17 +238,29 @@ impl Node for ShadowMapsPass {
 
         world.add_resource(self.atlas.clone());
 
+        // use a queue for storing atlas ids to add to entities after the entities are iterated
+        let mut index_components_queue = VecDeque::new();
+
         for (entity, pos, _) in world.view_iter::<(Entities, &Transform, Has<DirectionalLight>)>() {
             if !self.depth_maps.contains_key(&entity) {
-                self.create_depth_map(graph.device(), entity, *pos);
+               
+                // TODO: dont pack the textures as they're added
+                let atlas_index = self.create_depth_map(graph.device(), entity, *pos);
+                index_components_queue.push_back((entity, atlas_index));
+
                 debug!("Created depth map for {:?} light entity", entity);
             }
         }
+        
+        // now consume from the queue adding the components to the entities
+        while let Some((entity, atlas_id)) = index_components_queue.pop_front() {
+            world.insert(entity, LightShadowMapId(atlas_id));
+        }
 
         // update the light projection buffer slot
         let (_, dir_depth_map) = self.depth_maps.iter().next().unwrap();
         let val = graph
-            .slot_value_mut(ShadowMapsPassSlots::DirLightProjectionBuffer)
+            .slot_value_mut(ShadowMapsPassSlots::ShadowLightUniformsBuffer)
             .unwrap();
         *val = SlotValue::Buffer(dir_depth_map.light_projection_buffer.clone());
 
@@ -313,11 +333,12 @@ impl Node for ShadowMapsPass {
             .expect("missing directional light in scene");
 
         {
+            let atlas = self.atlas.get();
             let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                 label: Some("pass_shadow_map"),
                 color_attachments: &[],
                 depth_stencil_attachment: Some(wgpu::RenderPassDepthStencilAttachment {
-                    view: self.atlas.view(),
+                    view: atlas.view(),
                     depth_ops: Some(wgpu::Operations {
                         load: wgpu::LoadOp::Clear(1.0),
                         store: true,
@@ -326,7 +347,7 @@ impl Node for ShadowMapsPass {
                 }),
             });
             pass.set_pipeline(&pipeline);
-            let viewport = self.atlas.texture_viewport(0);
+            let viewport = atlas.texture_viewport(dir_depth_map.atlas_index);
             // only render to the light's map in the atlas
             pass.set_viewport(viewport.offset.x as _, viewport.offset.y as _, viewport.size.x as _, viewport.size.y as _, 0.0, 1.0);
             // only clear the light map in the atlas
@@ -371,3 +392,39 @@ impl Node for ShadowMapsPass {
         }
     }
 }
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+struct LightShadowUniform {
+    space_mat: glam::Mat4,
+    atlas_frame: AtlasViewport, // 2xUVec2 (4xf32), so no padding needed
+}
+
+/// A component that stores the ID of a shadow map in the shadow map atlas for the entities.
+/// 
+/// An entity owns a light. If that light casts shadows, this will contain the ID of the shadow
+/// map inside of the [`TextureAtlas`].
+#[derive(Debug, Default, Copy, Clone, Component)]
+pub struct LightShadowMapId(u64);
+
+impl Deref for LightShadowMapId {
+    type Target = u64;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+/// An ecs resource storing the [`TextureAtlas`] of shadow maps.
+#[derive(Clone)]
+pub struct LightShadowMapAtlas(Arc<RwLock<TextureAtlas>>);
+
+impl LightShadowMapAtlas {
+    pub fn get(&self) -> RwLockReadGuard<TextureAtlas> {
+        self.0.read().unwrap()
+    }
+
+    pub fn get_mut(&self) -> RwLockWriteGuard<TextureAtlas> {
+        self.0.write().unwrap()
+    }
+}

lyra-game/src/render/shaders/base.wgsl

@@ -22,6 +22,11 @@ struct VertexOutput {
     @location(3) frag_pos_light_space: vec4<f32>,
 }
 
+struct TextureAtlasFrame {
+    offset: vec2<u32>,
+    size: vec2<u32>,
+}
+
 struct TransformData {
     transform: mat4x4<f32>,
     normal_matrix: mat4x4<f32>,
@@ -82,7 +87,7 @@ fn vs_main(
     let normal_mat = mat3x3(normal_mat4[0].xyz, normal_mat4[1].xyz, normal_mat4[2].xyz);
     out.world_normal = normalize(normal_mat * model.normal, );
     
-    out.frag_pos_light_space = u_light_space_matrix * world_position;
+    out.frag_pos_light_space = u_light_shadow.light_space_matrix * world_position;
 
     return out;
 }
@@ -104,13 +109,10 @@ var t_diffuse: texture_2d<f32>;
 @group(0) @binding(2)
 var s_diffuse: sampler;
 
-/*@group(4) @binding(0)
+struct LightShadowMapUniform {
-var<uniform> u_material: Material;
+    light_space_matrix: mat4x4<f32>,
-
+    atlas_frame: TextureAtlasFrame,
-@group(5) @binding(0)
+}
-var t_specular: texture_2d<f32>;
-@group(5) @binding(1)
-var s_specular: sampler;*/
 
 @group(4) @binding(0)
 var<storage, read_write> u_light_indices: array<u32>;
@@ -122,7 +124,9 @@ var t_shadow_maps_atlas: texture_depth_2d;
 @group(5) @binding(1)
 var s_shadow_maps_atlas: sampler;
 @group(5) @binding(2)
-var<uniform> u_light_space_matrix: mat4x4<f32>;
+var<uniform> u_shadow_maps_atlas_size: vec2<u32>;
+@group(5) @binding(3)
+var<uniform> u_light_shadow: LightShadowMapUniform;
 
 @fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
@@ -149,36 +153,8 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
         let light: Light = u_lights.data[light_index];
 
         if (light.light_ty == LIGHT_TY_DIRECTIONAL) {
-            /*var proj_coords = in.frag_pos_light_space.xyz / in.frag_pos_light_space.w;
-            // for some reason the y component is clipped after transforming
-            proj_coords.y = -proj_coords.y;
-
-            // Remap xy to [0.0, 1.0]
-            let xy_remapped = proj_coords.xy * 0.5 + 0.5;
-            proj_coords.x = mix(0.0, 1024.0 / 4096.0, xy_remapped.x);
-            proj_coords.y = mix(0.0, 1024.0 / 4096.0, xy_remapped.y);
-
-            let closest_depth = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, proj_coords.xy, 0.0, vec2<i32>(0, 0));
-            let current_depth = proj_coords.z;
-
-            // use a bias to avoid shadow acne
             let light_dir = normalize(-light.direction);
-            let bias = max(0.05 * (1.0 - dot(in.world_normal, light_dir)), 0.005);  
+            let shadow = calc_shadow(in.world_normal, light_dir, in.frag_pos_light_space, u_light_shadow.atlas_frame);
-            var shadow = 0.0;
-            if current_depth - bias > closest_depth {
-                shadow = 1.0;
-            }
-
-            // dont cast shadows outside the light's far plane
-            if (proj_coords.z > 1.0) {
-                shadow = 0.0;
-            }
-
-            return vec4<f32>(vec3<f32>(closest_depth), 1.0);*/
-
-
-            let light_dir = normalize(-light.direction);
-            let shadow = calc_shadow(in.world_normal, light_dir, in.frag_pos_light_space);
             light_res += blinn_phong_dir_light(in.world_position, in.world_normal, light, u_material, specular_color, shadow);
         } else if (light.light_ty == LIGHT_TY_POINT) {
             light_res += blinn_phong_point_light(in.world_position, in.world_normal, light, u_material, specular_color);
@@ -191,7 +167,7 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
     return vec4<f32>(light_object_res, object_color.a);
 }
 
-fn calc_shadow(normal: vec3<f32>, light_dir: vec3<f32>, frag_pos_light_space: vec4<f32>) -> f32 {
+fn calc_shadow(normal: vec3<f32>, light_dir: vec3<f32>, frag_pos_light_space: vec4<f32>, atlas_region: TextureAtlasFrame) -> f32 {
     var proj_coords = frag_pos_light_space.xyz / frag_pos_light_space.w;
     // for some reason the y component is clipped after transforming
     proj_coords.y = -proj_coords.y;
@@ -203,20 +179,24 @@ fn calc_shadow(normal: vec3<f32>, light_dir: vec3<f32>, frag_pos_light_space: ve
 
     // Remap xy to [0.0, 1.0]
     let xy_remapped = proj_coords.xy * 0.5 + 0.5;
-     // TODO: when more lights are added, change the index, and the atlas sizes
+
-    let shadow_map_index = 0; 
+    // no need to get the y since the maps are square
-    let shadow_map_region = vec2<f32>( (f32(shadow_map_index) * 1024.0) / 4096.0, (f32(shadow_map_index + 1) * 1024.0) / 4096.0);
+    let atlas_start = f32(atlas_region.offset.x) / f32(u_shadow_maps_atlas_size.x);
+    let atlas_end = f32(atlas_region.offset.x + atlas_region.size.x) / f32(u_shadow_maps_atlas_size.x);
     // lerp the tex coords to the shadow map for this light.
-    proj_coords.x = mix(shadow_map_region.x, shadow_map_region.y, xy_remapped.x);
+    proj_coords.x = mix(atlas_start, atlas_end, xy_remapped.x);
-    proj_coords.y = mix(shadow_map_region.x, shadow_map_region.y, xy_remapped.y);
+    proj_coords.y = mix(atlas_start, atlas_end, xy_remapped.y);
 
     // simulate `ClampToBorder`, not creating shadows past the shadow map regions
-    if (proj_coords.x > shadow_map_region.y && proj_coords.y > shadow_map_region.y)
+    if (proj_coords.x > atlas_end && proj_coords.y > atlas_end)
-            || (proj_coords.x < shadow_map_region.x && proj_coords.y < shadow_map_region.x) {
+            || (proj_coords.x < atlas_start && proj_coords.y < atlas_start) {
         return 0.0;
     }
 
-    let closest_depth = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, proj_coords.xy, 0.0, vec2<i32>(0, 0));
+    // must manually apply offset to the texture coords since `textureSampleLevel` requires a
+    // const value.
+    let offset_coords = proj_coords.xy + (vec2<f32>(atlas_region.offset) / vec2<f32>(u_shadow_maps_atlas_size));
+    let closest_depth = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, offset_coords, 0.0);
     let current_depth = proj_coords.z;
 
     // use a bias to avoid shadow acne

lyra-game/src/render/shaders/shadows.wgsl

@@ -3,8 +3,18 @@ struct TransformData {
     normal_matrix: mat4x4<f32>,
 }
 
+struct TextureAtlasFrame {
+    offset: vec2<u32>,
+    size: vec2<u32>,
+}
+
+struct LightShadowMapUniform {
+    light_space_matrix: mat4x4<f32>,
+    atlas_frame: TextureAtlasFrame,
+}
+
 @group(0) @binding(0)
-var<uniform> u_light_space_matrix: mat4x4<f32>;
+var<uniform> u_light_shadow: LightShadowMapUniform;
 
 @group(1) @binding(0)
 var<uniform> u_model_transform_data: TransformData;
@@ -18,6 +28,6 @@ struct VertexOutput {
 fn vs_main(
     @location(0) position: vec3<f32>
 ) -> VertexOutput {
-    let pos = u_light_space_matrix * u_model_transform_data.transform * vec4<f32>(position, 1.0);
+    let pos = u_light_shadow.light_space_matrix * u_model_transform_data.transform * vec4<f32>(position, 1.0);
     return VertexOutput(pos);
 }

lyra-game/src/render/texture_atlas.rs

@@ -1,31 +1,54 @@
-use std::sync::Arc;
+use std::{
+    collections::BTreeMap,
+    sync::Arc,
+};
 
 use glam::UVec2;
+use rectangle_pack::{pack_rects, GroupedRectsToPlace, RectToInsert, RectanglePackOk, TargetBin};
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, thiserror::Error)]
+pub enum AtlasPackError {
+    /// The rectangles can't be placed into the atlas. The atlas must increase in size
+    #[error("There is not enough space in the atlas for the textures")]
+    NotEnoughSpace,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct AtlasViewport {
     pub offset: UVec2,
     pub size: UVec2,
 }
 
 pub struct TextureAtlas {
-    /// The size of each texture in the atlas.
+    atlas_size: UVec2,
-    texture_size: UVec2,
-    /// The amount of textures in the atlas.
-    texture_count: UVec2,
 
     texture_format: wgpu::TextureFormat,
     texture: Arc<wgpu::Texture>,
     view: Arc<wgpu::TextureView>,
+
+    /// The next id of the next texture that will be added to the atlas.
+    next_texture_id: u64,
+
+    rects: GroupedRectsToPlace<u64>,
+    bins: BTreeMap<u64, TargetBin>,
+    placement: Option<RectanglePackOk<u64, u64>>,
 }
 
 impl TextureAtlas {
-    pub fn new(device: &wgpu::Device, format: wgpu::TextureFormat, usages: wgpu::TextureUsages, texture_size: UVec2, texture_count: UVec2) -> Self {
+    pub fn new(
-        let total_size = texture_size * texture_count;
+        device: &wgpu::Device,
-        
+        format: wgpu::TextureFormat,
+        usages: wgpu::TextureUsages,
+        atlas_size: UVec2,
+    ) -> Self {
         let texture = device.create_texture(&wgpu::TextureDescriptor {
             label: Some("texture_atlas"),
-            size: wgpu::Extent3d { width: total_size.x, height: total_size.y, depth_or_array_layers: 1 },
+            size: wgpu::Extent3d {
+                width: atlas_size.x,
+                height: atlas_size.y,
+                depth_or_array_layers: 1,
+            },
             mip_level_count: 1,
             sample_count: 1,
             dimension: wgpu::TextureDimension::D2,
@@ -35,21 +58,98 @@ impl TextureAtlas {
         });
         let view = texture.create_view(&wgpu::TextureViewDescriptor::default());
 
+        let mut bins = BTreeMap::new();
+        // max_depth=1 for 2d
+        bins.insert(0, TargetBin::new(atlas_size.x, atlas_size.y, 1));
+
         Self {
-            texture_size,
+            atlas_size,
-            texture_count,
             texture_format: format,
             texture: Arc::new(texture),
             view: Arc::new(view),
+            next_texture_id: 0,
+            rects: GroupedRectsToPlace::new(),
+            bins,
+            placement: None,
         }
     }
 
-    /// Get the viewport of a texture index in the atlas.
+    /// Add a texture of `size` and pack it into the atlas, returning the id of the texture in
-    pub fn texture_viewport(&self, atlas_index: u32) -> AtlasViewport {
+    /// the atlas.
-        let x = (atlas_index % self.texture_count.x) * self.texture_size.x;
+    /// 
-        let y = (atlas_index / self.texture_count.y) * self.texture_size.y;
+    /// If you are adding multiple textures at a time and want to wait to pack the atlas, use
+    /// [`TextureAtlas::add_texture_unpacked`] and then after you're done adding them, pack them
+    /// with [`TextureAtlas::pack_atlas`].
+    pub fn pack_new_texture(&mut self, width: u32, height: u32) -> Result<u64, AtlasPackError> {
+        let id = self.next_texture_id;
+        self.next_texture_id += 1;
 
-        AtlasViewport { offset: UVec2::new(x, y), size: self.texture_size }
+        // for 2d rects, set depth to 1
+        let r = RectToInsert::new(width, height, 1);
+        self.rects.push_rect(id, None, r);
+
+        self.pack_atlas()?;
+
+        Ok(id)
+    }
+
+    /// Add a new texture and **DO NOT** pack it into the atlas.
+    /// 
+    /// <div class="warning">
+    /// 
+    /// The texture will not be packed into the atlas meaning
+    /// [`TextureAtlas::texture_viewport`] will return `None`. To pack the texture,
+    /// use [`TextureAtlas::pack_atlas`] or use [`TextureAtlas::pack_new_texture`]
+    /// when only adding a single texture.
+    /// 
+    /// </div>
+    pub fn add_texture_unpacked(&mut self, width: u32, height: u32) -> Result<u64, AtlasPackError> {
+        let id = self.next_texture_id;
+        self.next_texture_id += 1;
+
+        // for 2d rects, set depth to 1
+        let r = RectToInsert::new(width, height, 1);
+        self.rects.push_rect(id, None, r);
+
+        self.pack_atlas()?;
+
+        Ok(id)
+    }
+
+    /// Pack the textures into the atlas.
+    pub fn pack_atlas(&mut self) -> Result<(), AtlasPackError> {
+        let placement = pack_rects(
+            &self.rects,
+            &mut self.bins,
+            &rectangle_pack::volume_heuristic,
+            &rectangle_pack::contains_smallest_box,
+        )
+        .map_err(|e| match e {
+            rectangle_pack::RectanglePackError::NotEnoughBinSpace => AtlasPackError::NotEnoughSpace,
+        })?;
+        self.placement = Some(placement);
+
+        Ok(())
+    }
+
+    /// Get the viewport of a texture index in the atlas.
+    pub fn texture_viewport(&self, atlas_index: u64) -> AtlasViewport {
+        let locations = self.placement.as_ref().unwrap().packed_locations();
+        let (bin_id, loc) = locations
+            .get(&atlas_index)
+            .expect("atlas index is incorrect");
+        debug_assert_eq!(*bin_id, 0, "somehow the texture was put in some other bin");
+
+        AtlasViewport {
+            offset: UVec2 {
+                x: loc.x(),
+                y: loc.y(),
+            },
+            size: UVec2 {
+                x: loc.width(),
+                y: loc.height(),
+            },
+        }
     }
 
     pub fn view(&self) -> &Arc<wgpu::TextureView> {
@@ -64,15 +164,12 @@ impl TextureAtlas {
         &self.texture_format
     }
 
-    pub fn texture_size(&self) -> UVec2 {
+    pub fn total_texture_count(&self) -> u64 {
-        self.texture_size
+        self.next_texture_id // starts at zero, so no need to increment
     }
 
-    pub fn texture_count(&self) -> UVec2 {
+    /// Returns the size of the entire texture atlas.
-        self.texture_count
+    pub fn atlas_size(&self) -> UVec2 {
+        self.atlas_size
     }
-
+}
-    pub fn total_texture_count(&self) -> u32 {
-        self.texture_count.x * self.texture_count.y
-    }
-}