feat(renderer): add ORM and emissive texture map support to PBR pipeline

- Extended bind group 1: albedo + normal + ORM + emissive (8 bindings)
- pbr_shader.wgsl: ORM sampling (R=AO, G=roughness, B=metallic) + emissive
- deferred_gbuffer.wgsl: ORM + emissive luminance in material_data.w
- deferred_lighting.wgsl: emissive contribution from G-Buffer
- All 5 PBR examples updated with default ORM/emissive textures
- Backward compatible: old 4-binding layout preserved

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

examples/multi_light_demo/src/main.rs

@@ -11,7 +11,7 @@ use voltex_renderer::{
     GpuContext, Camera, FpsController, CameraUniform, LightsUniform, LightData,
     Mesh, GpuTexture, MaterialUniform, generate_sphere, create_pbr_pipeline, obj,
     ShadowMap, ShadowUniform,
-    IblResources, pbr_texture_bind_group_layout, create_pbr_texture_bind_group,
+    IblResources, pbr_full_texture_bind_group_layout, create_pbr_full_texture_bind_group,
 };
 use wgpu::util::DeviceExt;
 
@@ -35,6 +35,8 @@ struct AppState {
     camera_light_bind_group: wgpu::BindGroup,
     _albedo_tex: GpuTexture,
     _normal_tex: (wgpu::Texture, wgpu::TextureView, wgpu::Sampler),
+    _orm_tex: GpuTexture,
+    _emissive_tex: GpuTexture,
     pbr_texture_bind_group: wgpu::BindGroup,
     material_bind_group: wgpu::BindGroup,
     shadow_bind_group: wgpu::BindGroup,
@@ -149,7 +151,7 @@ impl ApplicationHandler for MultiLightApp {
 
         // Bind group layouts
         let cl_layout = camera_light_bind_group_layout(&gpu.device);
-        let pbr_tex_layout = pbr_texture_bind_group_layout(&gpu.device);
+        let pbr_tex_layout = pbr_full_texture_bind_group_layout(&gpu.device);
         let mat_layout = MaterialUniform::bind_group_layout(&gpu.device);
 
         // Camera+Light bind group
@@ -174,17 +176,23 @@ impl ApplicationHandler for MultiLightApp {
             ],
         });
 
-        // PBR texture bind group (albedo + normal)
+        // PBR texture bind group (albedo + normal + ORM + emissive)
         let old_tex_layout = GpuTexture::bind_group_layout(&gpu.device);
         let albedo_tex = GpuTexture::white_1x1(&gpu.device, &gpu.queue, &old_tex_layout);
         let normal_tex = GpuTexture::flat_normal_1x1(&gpu.device, &gpu.queue);
-        let pbr_texture_bind_group = create_pbr_texture_bind_group(
+        let orm_tex = GpuTexture::white_1x1(&gpu.device, &gpu.queue, &old_tex_layout);
+        let emissive_tex = GpuTexture::black_1x1(&gpu.device, &gpu.queue, &old_tex_layout);
+        let pbr_texture_bind_group = create_pbr_full_texture_bind_group(
             &gpu.device,
             &pbr_tex_layout,
             &albedo_tex.view,
             &albedo_tex.sampler,
             &normal_tex.1,
             &normal_tex.2,
+            &orm_tex.view,
+            &orm_tex.sampler,
+            &emissive_tex.view,
+            &emissive_tex.sampler,
         );
 
         // IBL resources
@@ -252,6 +260,8 @@ impl ApplicationHandler for MultiLightApp {
             camera_light_bind_group,
             _albedo_tex: albedo_tex,
             _normal_tex: normal_tex,
+            _orm_tex: orm_tex,
+            _emissive_tex: emissive_tex,
             pbr_texture_bind_group,
             material_bind_group,
             shadow_bind_group,