ios - 在 iOS Metal 中重用具有不同统一参数的像素着色器

Question

我在跨具有不同统一参数的不同对象重用我的 Metal 像素和顶点着色器时遇到问题。我猜这与我错误地使用命令缓冲区有关。

当我运行我的 Metal 应用程序时，几何图形绘制正确，但只有最终调用的制服

renderCommand setFragmentBuffer:uniform_info offset:0 atIndex:UNIFORM_INFO_BUFFER_INDEX];

似乎在向像素着色器写入数据。

我在这里剪切粘贴(并编辑)了我的渲染循环。我正在寻找一个示例，说明如何在传入不同制服的单个渲染过程中多次重复使用我的像素着色器。

  CAMetalLayer *metalLayer = [metal_info.g_iosMetalView getMetalLayer];

  id <CAMetalDrawable> frameDrawable;
  while (!frameDrawable){
     frameDrawable = [metalLayer nextDrawable];
  }
  MTLRenderPassDescriptor *mtlRenderPassDescriptor;
  mtlRenderPassDescriptor = [MTLRenderPassDescriptor new];
  mtlRenderPassDescriptor.colorAttachments[0].texture = frameDrawable.texture;
  mtlRenderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionLoad;
  mtlRenderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0.0, 0.0, 1.0, 1.0);

  mtlRenderPassDescriptor.depthAttachment.texture = metal_info.g_depthTexture;
  mtlRenderPassDescriptor.depthAttachment.loadAction = MTLLoadActionClear;
  mtlRenderPassDescriptor.depthAttachment.storeAction = MTLStoreActionStore;
  mtlRenderPassDescriptor.depthAttachment.clearDepth = 1.0;

  // Create My one and only command buffer
  id <MTLCommandBuffer> mtlCommandBuffer = [metal_info.g_commandQueue commandBuffer];

  int n = RendererInfo.fact.GetActiveCount();

  // loop through all the objects I have (I'm having trouble with 2)
  Object* curObj = NULL;
  for (int obj_i = 0 ; obj_i < n ; ++obj_i)
  {
     // create one render encoder for each object
     id <MTLRenderCommandEncoder> renderCommand = [mtlCommandBuffer renderCommandEncoderWithDescriptor: mtlRenderPassDescriptor];

     memcpy([metal_info.g_projectionMatrix contents], &metal_info.g_Projection, sizeof(Matrix4f));         
     Matrix4f *view = RendererInfo.cam->GetViewMatrix();
     memcpy([metal_info.g_viewMatrix contents], view, sizeof(Matrix4f));

     [renderCommand setFrontFacingWinding:MTLWindingCounterClockwise];
     [renderCommand setCullMode:MTLCullModeBack]; 

     [renderCommand setViewport: (MTLViewport){ 0.0, 0.0,
        (double)metal_info.g_metal_width,
        (double)metal_info.g_metal_height,
        0.0, 1.0 }];

     [renderCommand setRenderPipelineState:metal_info.g_pipelineState];
     [renderCommand setDepthStencilState:metal_info.g_depthState];


     curObj = RendererInfo.fact.GetObjectAtIndex(obj_i);

     id<MTLBuffer> vertices = curObj->GetVertexBuffer();
     id<MTLBuffer> indicies = curObj->GetIndexBuffer();         
     int indexCount = curObj->GetIndexCount();

     id <MTLTexture> texture = objTexture->GetAsset();
     [renderCommand setFragmentTexture:texture atIndex:0];         

     memcpy([metal_info.g_shaderUniformInfo contents], curObj->GetUniformInfo(), curObj->curObj->GetUniformInfoSize());

     [renderCommand setVertexBuffer:vertices                       offset:0 atIndex:VERTICES__INDEX];
     [renderCommand setVertexBuffer:metal_info.g_viewMatrix        offset:0 atIndex:VIEW_MATRIX_BUFFER_INDEX];
     [renderCommand setVertexBuffer:metal_info.g_projectionMatrix  offset:0 atIndex:PROJECTION_MATRIX_BUFFER_INDEX];

     [renderCommand setFragmentBuffer:metal_info.g_shaderUniformInfo  offset:0 atIndex:UNIFORM_INFO_BUFFER_INDEX];

     [renderCommand drawIndexedPrimitives:MTLPrimitiveTypeTriangle
                               indexCount:indexCount
                               indexType:MTLIndexTypeUInt32
                             indexBuffer:indicies
                       indexBufferOffset:0];

     [renderCommand endEncoding];
  }
  [mtlCommandBuffer presentDrawable:frameDrawable];
  [mtlCommandBuffer commit];

如果您愿意，我也可以发布像素着色器，但是当我编码为一次只渲染一个对象时，着色器可以正常工作。

Answer 1

MTLRenderCommandEncoder 不对“memcpy”指令进行编码。您目前认为每个 memcpy([metal_info.g_shaderUniformInfo contents], curObj->GetUniformInfo(), curObj->curObj->GetUniformInfoSize()); 都与编码器相关联，但实际上，您只是将相同的 metal_info.g_shaderUniformInfo 与每个编码器相关联，并且着色器都在使用来自该缓冲区的数据，在提交命令缓冲区之后 – 编码器不会捕获缓冲区的副本。您注意到的关键是，此提交发生在您最后一次运行循环之后，此时 g_shaderUniformInfo 具有唯一可以有意义地使用的值。

您需要为每个对象使用不同的统一缓冲区，或者写入同一缓冲区的不同部分，然后适本地从中读取。