I've downloaded Apple's metal simulator example from here https://developer.apple.com/documentation/metal/supporting_simulator_in_a_metal_app and tried simulating an iphone 11 with 11.5 and 12 using iOS, and iPad 9th gen. I get the error below when running the simulator on all the above devices. -[MTLDebugRenderCommandEncoder validateCommonDrawErrors:]:5252: failed assertion `Draw Errors Validation Fragment Function(blendFragmentShader): Shader reads texture (prevColor[1]) whose usage (0x04) doesn't specify MTLTextureUsageShaderRead (0x01) The error occurs in the drawBox:rendererEncoder at the code below when boxIndex = 1 for(MTKSubmesh *submesh in _meshes[boxIndex].submeshes)   {     [renderEncoder drawIndexedPrimitives:submesh.primitiveType                  indexCount:submesh.indexCount                   indexType:submesh.indexType                  indexBuffer:submesh.indexBuffer.buffer               indexBufferOffset:submesh.indexBuffer.offset];   } I'm using a Macbook pro, macos 12.2 and Xcode 13.3. I hoped that this example would be an easy way to get experience with metal, but I've not got the experience I need to interpret what I should change to address the "doesn't specify MTLTextureUsageShaderRead" error. Any help is greatly appreciated.