add Default miplevel and array layer

filament/backend/src/webgpu/WebGPUDriver.cpp

@@ -431,18 +431,6 @@ void WebGPUDriver::createDefaultRenderTargetR(Handle<HwRenderTarget> rth, int) {
 void WebGPUDriver::createRenderTargetR(Handle<HwRenderTarget> rth, TargetBufferFlags targets,
         uint32_t width, uint32_t height, uint8_t samples, uint8_t layerCount, MRT color,
         TargetBufferInfo depth, TargetBufferInfo stencil) {
-    // The `targets` flags indicate which of the `color`, `depth`, `stencil` TargetBufferInfo
-    // are actually active for this render target.
-    // We'll pass all TargetBufferInfo to WGPURenderTarget; it will use them if their handles are valid.
-
-    // Ensure that textures intended for use as attachments were created with
-    // wgpu::TextureUsage::RenderAttachment. This check should ideally be in createTextureR
-    // or validated here if possible.
-
-    // The `layerCount` parameter might be for creating array textures that this RT targets.
-    // Individual attachments (color[i].layer, depth.layer, stencil.layer) specify which layer
-    // of an array texture to bind. For now, we assume textures are pre-configured.
-
     constructHandle<WGPURenderTarget>(rth, width, height, samples, layerCount, color, depth, stencil);
 }
 

filament/backend/src/webgpu/WebGPUHandles.cpp

@@ -638,7 +638,8 @@ WGPUTexture::WGPUTexture(SamplerType samplerType, uint8_t levels, TextureFormat
     FILAMENT_CHECK_POSTCONDITION(mTexture)
             << "Failed to create texture for " << textureDescriptor.label;
 
-    mDefaultTextureView = makeTextureView(0, levels, 0, mArrayLayerCount, samplerType);
+    mDefaultTextureView = makeTextureView(mDefaultMipLevel, levels, mDefaultBaseArrayLayer,
+            mArrayLayerCount, samplerType);
 }
 
 WGPUTexture::WGPUTexture(WGPUTexture* src, uint8_t baseLevel, uint8_t levelCount) noexcept
@@ -977,7 +978,10 @@ wgpu::TextureAspect WGPUTexture::fToWGPUTextureViewAspect(TextureUsage const& fU
 }
 
 wgpu::TextureView WGPUTexture::getOrMakeTextureView(uint8_t mipLevel, uint32_t arrayLayer) const {
-//    TODO: just return mTextureView if redundant
+    //TODO: there's an optimization to be made here to return mDefaultTextureView.
+    // Problem: mDefaultTextureView is a view of the entire texture,
+    // but this function (and its callers) expects a single-slice view.
+    // Returning the whole texture view for a single-slice request seems wrong.
 
     return makeTextureView(mipLevel, 1, arrayLayer, 1, mSamplerType);
 }

filament/backend/src/webgpu/WebGPUHandles.h

@@ -208,7 +208,8 @@ private:
     size_t mBlockHeight;
     SamplerType mSamplerType;
     wgpu::TextureView mDefaultTextureView = nullptr;
-
+    uint32_t mDefaultMipLevel = 0;
+    uint32_t mDefaultBaseArrayLayer = 0;
 
     [[nodiscard]] wgpu::TextureUsage fToWGPUTextureUsage(
             filament::backend::TextureUsage const& fUsage);