如何以bgra8Unorm像素格式绘制MTLTexture [英] How to draw on MTLTexture in bgra8Unorm pixel format

问题描述

当我使用 rgba32Float 像素格式的 MTLTexture 绘制代码时，我的代码可以正常工作，然后可以从其中删除 CVPixelBuffer .

但是 FlutterTexture 需要 bgra8Unorm 格式.由于性能开销，我不想转换 CVPixelBuffer .

因此，我尝试使用 bgra8Unorm 像素格式在 MTLTexture 上进行渲染，但是以下片段着色器代码无法编译:

 片段vector_uchar4fragmentShader2(顶点内插[[stage_in]]){返回0xFFFFFFFF;} 

有错误:片段函数的无效返回类型'vector_uchar4'我尝试将其替换为 uint 类型，但是由于崩溃而崩溃:

 致命错误:尝试！"表达式意外引发错误:错误域= AGXMetalA11代码= 3"uint类型的输出与MTLPixelFormatBGRA8Unorm颜色附件不兼容."UserInfo = {NSLocalizedDescription = uint类型的输出与MTLPixelFormatBGRA8Unorm颜色附件不兼容.} 

如果我使用 vector_float4 或 vector_half4 返回类型，则我的纹理和缓冲区为空.

我必须将哪种返回类型用于 bgra8Unorm 像素格式并获取非空图像?完全可以用金属吗?

解决方案

我在

最后，此代码按预期绘制图像:

 片段float4fragmentShader2(顶点内插[[stage_in]]){//...rgba8unorm< float4>rgba;rgba = float4(color.r，color.g，color.b，1.0);返回rgba;} 

如果有人可以解释幕后发生的事情，我真的很想不浪费金钱.

My code works when I draw on MTLTexture with rgba32Float pixel format, I can take then CVPixelBuffer out of it.

But FlutterTexture requires bgra8Unorm format. I do not want to convert CVPixelBuffer due to performance overhead.

So I'm trying to render on MTLTexture with bgra8Unorm pixel format, but the following fragment shader code won't compile:

fragment vector_uchar4 fragmentShader2(Vertex interpolated [[stage_in]]) {
    return 0xFFFFFFFF;
}

With error: Invalid return type 'vector_uchar4' for fragment function I've tried to replace it with uint type, but it crashes with error:

Fatal error: 'try!' expression unexpectedly raised an error:
Error Domain=AGXMetalA11 Code=3 
"output of type uint is not compatible with a MTLPixelFormatBGRA8Unorm color attachement."
UserInfo={NSLocalizedDescription=output of type uint is not compatible with a MTLPixelFormatBGRA8Unorm color attachement.}

If I use vector_float4 or vector_half4 return type my texture and buffers are empty.

Which return type I have to use for bgra8Unorm pixel format and get non empty image? Is it possible with metal at all?

解决方案

I've found answer on page 30 of Metal Shading Language specification

And finally this code draws image as expected:

fragment float4 fragmentShader2(Vertex interpolated [[stage_in]]) {
    // ...
    rgba8unorm<float4> rgba;
    rgba = float4(color.r, color.g, color.b, 1.0);
    return rgba;
}

If someone can explain what is happening under the hood, I would really like to not waste bounty.

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