fix(renderer): merge IBL into group(3) to stay within max_bind_groups limit of 4

wgpu's default max_bind_groups is 4 (groups 0-3), but the PBR shader was
using group(4) for BRDF LUT bindings. This merges IBL bindings into the
shadow bind group (group 3) at binding slots 3-4, removes the standalone
IBL bind group layout/creation, and updates all examples accordingly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/voltex_renderer/src/ibl.rs

@@ -79,51 +79,4 @@ impl IblResources {
         }
     }
 
-    /// Bind group layout for group(4):
-    ///   binding 0 — texture_2d<f32> (filterable)
-    ///   binding 1 — sampler (filtering)
-    pub fn bind_group_layout(device: &wgpu::Device) -> wgpu::BindGroupLayout {
-        device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
-            label: Some("IblBindGroupLayout"),
-            entries: &[
-                wgpu::BindGroupLayoutEntry {
-                    binding: 0,
-                    visibility: wgpu::ShaderStages::FRAGMENT,
-                    ty: wgpu::BindingType::Texture {
-                        multisampled: false,
-                        view_dimension: wgpu::TextureViewDimension::D2,
-                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
-                    },
-                    count: None,
-                },
-                wgpu::BindGroupLayoutEntry {
-                    binding: 1,
-                    visibility: wgpu::ShaderStages::FRAGMENT,
-                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
-                    count: None,
-                },
-            ],
-        })
-    }
-
-    pub fn create_bind_group(
-        &self,
-        device: &wgpu::Device,
-        layout: &wgpu::BindGroupLayout,
-    ) -> wgpu::BindGroup {
-        device.create_bind_group(&wgpu::BindGroupDescriptor {
-            label: Some("IblBindGroup"),
-            layout,
-            entries: &[
-                wgpu::BindGroupEntry {
-                    binding: 0,
-                    resource: wgpu::BindingResource::TextureView(&self.brdf_lut_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 1,
-                    resource: wgpu::BindingResource::Sampler(&self.brdf_lut_sampler),
-                },
-            ],
-        })
-    }
 }

crates/voltex_renderer/src/pbr_pipeline.rs

@@ -8,7 +8,6 @@ pub fn create_pbr_pipeline(
     texture_layout: &wgpu::BindGroupLayout,
     material_layout: &wgpu::BindGroupLayout,
     shadow_layout: &wgpu::BindGroupLayout,
-    ibl_layout: &wgpu::BindGroupLayout,
 ) -> wgpu::RenderPipeline {
     let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
         label: Some("PBR Shader"),
@@ -17,7 +16,7 @@ pub fn create_pbr_pipeline(
 
     let layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
         label: Some("PBR Pipeline Layout"),
-        bind_group_layouts: &[camera_light_layout, texture_layout, material_layout, shadow_layout, ibl_layout],
+        bind_group_layouts: &[camera_light_layout, texture_layout, material_layout, shadow_layout],
         immediate_size: 0,
     });
 

crates/voltex_renderer/src/pbr_shader.wgsl

@@ -48,9 +48,8 @@ struct ShadowUniform {
 @group(3) @binding(0) var t_shadow: texture_depth_2d;
 @group(3) @binding(1) var s_shadow: sampler_comparison;
 @group(3) @binding(2) var<uniform> shadow: ShadowUniform;
-
-@group(4) @binding(0) var t_brdf_lut: texture_2d<f32>;
-@group(4) @binding(1) var s_brdf_lut: sampler;
+@group(3) @binding(3) var t_brdf_lut: texture_2d<f32>;
+@group(3) @binding(4) var s_brdf_lut: sampler;
 
 struct VertexInput {
     @location(0) position: vec3<f32>,

crates/voltex_renderer/src/shadow.rs

@@ -78,6 +78,24 @@ impl ShadowMap {
                     },
                     count: None,
                 },
+                // binding 3: BRDF LUT texture
+                wgpu::BindGroupLayoutEntry {
+                    binding: 3,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Texture {
+                        multisampled: false,
+                        view_dimension: wgpu::TextureViewDimension::D2,
+                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
+                    },
+                    count: None,
+                },
+                // binding 4: BRDF LUT sampler
+                wgpu::BindGroupLayoutEntry {
+                    binding: 4,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
+                    count: None,
+                },
             ],
         })
     }
@@ -87,6 +105,8 @@ impl ShadowMap {
         device: &wgpu::Device,
         layout: &wgpu::BindGroupLayout,
         shadow_uniform_buffer: &wgpu::Buffer,
+        brdf_lut_view: &wgpu::TextureView,
+        brdf_lut_sampler: &wgpu::Sampler,
     ) -> wgpu::BindGroup {
         device.create_bind_group(&wgpu::BindGroupDescriptor {
             label: Some("Shadow Bind Group"),
@@ -104,6 +124,14 @@ impl ShadowMap {
                     binding: 2,
                     resource: shadow_uniform_buffer.as_entire_binding(),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: wgpu::BindingResource::TextureView(brdf_lut_view),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 4,
+                    resource: wgpu::BindingResource::Sampler(brdf_lut_sampler),
+                },
             ],
         })
     }