启用像素混合与MSAA时背面边缘出现奇怪阶梯状效果

启用像素混合和MSAA后，背面边缘的抗锯齿效果异常，可见1像素宽的内部深灰色线条。以下截图中红线标注了异常位置：

这是通过PIX截取的红色立方体内部边缘放大图：

PIX显示边缘alpha值为0.5（符合预期），但颜色存在异常变化。

异常触发条件：

• 仅同时启用MSAA和像素混合时出现，禁用MSAA后一切正常
• 仅在NVIDIA专用显卡（如GTX 1060）上出现，Intel 630集成显卡无此问题
• 更新NVIDIA驱动无效，其他使用NVIDIA GPU的用户也能复现该问题

有人遇到过此类问题吗？如何调试问题根源？

以下是PSO创建的代码示例：

// Setup rasterizer description.
CD3DX12_RASTERIZER_DESC rasterizerDesc(D3D12_DEFAULT);
rasterizerDesc.CullMode = D3D12_CULL_MODE_NONE;
rasterizerDesc.FillMode = D3D12_FILL_MODE_SOLID;
rasterizerDesc.MultisampleEnable = 1;
psoDesc.RasterizerState = rasterizerDesc;

// Setup pixel blend description.
psoDesc.BlendState = CD3DX12_BLEND_DESC(D3D12_DEFAULT);
D3D12_RENDER_TARGET_BLEND_DESC blendDesc;
blendDesc.BlendEnable = 1;
blendDesc.LogicOpEnable = 0;
blendDesc.SrcBlend = D3D12_BLEND_SRC_ALPHA;
blendDesc.DestBlend = D3D12_BLEND_INV_SRC_ALPHA;
blendDesc.BlendOp = D3D12_BLEND_OP_ADD;
blendDesc.SrcBlendAlpha = D3D12_BLEND_ONE;
blendDesc.DestBlendAlpha = D3D12_BLEND_ZERO;
blendDesc.BlendOpAlpha = D3D12_BLEND_OP_ADD;
blendDesc.LogicOp = D3D12_LOGIC_OP_NOOP;
blendDesc.RenderTargetWriteMask = D3D12_COLOR_WRITE_ENABLE_ALL;
psoDesc.BlendState.RenderTarget[0] = blendDesc;
psoDesc.BlendState.AlphaToCoverageEnable = 0;

// Finalize PSO description.
psoDesc.DepthStencilState = CD3DX12_DEPTH_STENCIL_DESC(D3D12_DEFAULT);
// Disable depth writes.
psoDesc.DepthStencilState.DepthWriteMask = D3D12_DEPTH_WRITE_MASK_ZERO;
psoDesc.SampleMask = UINT_MAX;
psoDesc.PrimitiveTopologyType = D3D12_PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE;
psoDesc.NumRenderTargets = 1;
psoDesc.RTVFormats[0] = DXGI_FORMAT_R8G8B8A8_UNORM;
psoDesc.SampleDesc.Count = 8;
psoDesc.SampleDesc.Quality = iMsaaQualityLevelsCount - 1;
psoDesc.DSVFormat = DXGI_FORMAT_D24_UNORM_S8_UINT;

MSAA渲染目标资源也启用了相同的样本数/质量等级。

内容的提问来源于stack exchange，提问作者Flone