MTLTextureDescriptor难题

Question

我尝试将"Metal By Example“App -TextRendering- for IOS转换为OSX。不幸的是，Xcode告诉我MTLTextureDescriptor的storageMode需要设置为MTLStorageModePrivate，当我这样做的时候:MTLTextureDescriptor抛出"failed assertion ` `CPU access for textures with MTLResourceStorageModePrivate storage mode is disallowed“。

MTLTextureDescriptor *textureDesc = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:AAPLDepthPixelFormat
            width:MBEFontAtlasSize
            height:MBEFontAtlasSize
            mipmapped:NO];
            
        textureDesc.storageMode = MTLStorageModePrivate;
        textureDesc.usage = MTLTextureUsageRenderTarget | MTLTextureUsageShaderRead | MTLTextureUsageShaderWrite;
        textureDesc.usage = MTLTextureUsageShaderRead;//MTLTextureUsageRenderTarget;
    
        MTLRegion region = MTLRegionMake2D(0, 0, MBEFontAtlasSize, MBEFontAtlasSize);
        _fontTexture = [_device newTextureWithDescriptor:textureDesc];
        [_fontTexture setLabel:@"Font Atlas"];
        [_fontTexture replaceRegion:region mipmapLevel:0 withBytes:_fontAtlas.textureData.bytes bytesPerRow:MBEFontAtlasSize];

任何帮助都将不胜感激！

Answer 1

在macOS上，您实际上必须显式地在CPU/RAM和GPU之间同步资源(因为Mac可能有一个拥有自己内存的专用GPU，而不是iOS上的共享内存模型)。

为此，您需要将存储模式设置为managed，并使用MTLBlitCommandEncoder在设备之间复制内存(请参阅documentation of managed)。