Support multi-layered render target (#8108)

Clients can create a multi-layered render target that consists of array
textures, and use it as a custom render target.

A new sample app "hellostereo" demonstrates how to use this feature.

NEW_RELEASE_NOTES.md

@@ -7,3 +7,5 @@ for next branch cut* header.
 appropriate header in [RELEASE_NOTES.md](./RELEASE_NOTES.md).
 
 ## Release notes for next branch cut
+
+- Add support for multi-layered render target with array textures.

filament/src/details/RenderTarget.cpp

@@ -34,7 +34,7 @@ struct RenderTarget::BuilderDetails {
     uint32_t mWidth{};
     uint32_t mHeight{};
     uint8_t mSamples = 1;   // currently not settable in the public facing API
-    uint8_t mLayerCount = 0;// currently not settable in the public facing API
+    uint8_t mLayerCount = 1;
 };
 
 using BuilderType = RenderTarget;
@@ -91,22 +91,28 @@ RenderTarget* RenderTarget::Builder::build(Engine& engine) {
     uint32_t maxWidth = 0;
     uint32_t minHeight = std::numeric_limits<uint32_t>::max();
     uint32_t maxHeight = 0;
+    uint32_t minDepth = std::numeric_limits<uint32_t>::max();
+    uint32_t maxDepth = 0;
     for (auto const& attachment : mImpl->mAttachments) {
         if (attachment.texture) {
             const uint32_t w = attachment.texture->getWidth(attachment.mipLevel);
             const uint32_t h = attachment.texture->getHeight(attachment.mipLevel);
+            const uint32_t d = attachment.texture->getDepth(attachment.mipLevel);
             minWidth  = std::min(minWidth, w);
             minHeight = std::min(minHeight, h);
+            minDepth = std::min(minDepth, d);
             maxWidth  = std::max(maxWidth, w);
             maxHeight = std::max(maxHeight, h);
+            maxDepth = std::max(maxDepth, d);
         }
     }
 
-    FILAMENT_CHECK_PRECONDITION(minWidth == maxWidth && minHeight == maxHeight)
-            << "All attachments dimensions must match";
+    FILAMENT_CHECK_PRECONDITION(minWidth == maxWidth && minHeight == maxHeight
+            && minDepth == maxDepth) << "All attachments dimensions must match";
 
     mImpl->mWidth  = minWidth;
     mImpl->mHeight = minHeight;
+    mImpl->mLayerCount = minDepth;
     return downcast(engine).createRenderTarget(*this);
 }
 

samples/CMakeLists.txt

@@ -22,6 +22,7 @@ set(MATERIAL_SRCS
         materials/bakedTexture.mat
         materials/pointSprites.mat
         materials/aoPreview.mat
+        materials/arrayTexture.mat
         materials/groundShadow.mat
         materials/heightfield.mat
         materials/image.mat
@@ -252,6 +253,7 @@ if (NOT ANDROID)
     add_demo(helloskinning)
     add_demo(helloskinningbuffer)
     add_demo(helloskinningbuffer_morebones)
+    add_demo(hellostereo)
     add_demo(image_viewer)
     add_demo(lightbulb)
     add_demo(material_sandbox)
@@ -274,6 +276,7 @@ if (NOT ANDROID)
     target_link_libraries(gltf_viewer PRIVATE gltf-demo-resources uberarchive gltfio viewer)
     target_link_libraries(gltf_instances PRIVATE gltf-demo-resources uberarchive gltfio viewer)
     target_link_libraries(hellopbr PRIVATE filameshio suzanne-resources)
+    target_link_libraries(hellostereo PRIVATE filameshio suzanne-resources)
     target_link_libraries(image_viewer PRIVATE viewer imageio)
     target_link_libraries(multiple_windows PRIVATE filameshio suzanne-resources)
     target_link_libraries(rendertarget PRIVATE filameshio suzanne-resources)