为什么我的计算着色器不做任何事情？

Question

我使用的是 OpenGL 4.5（c# 中的 OpenGL.net，但代码与普通的 OpenGL 代码非常相似），并且正在尝试使用计算着色器。到目前为止，这是我所拥有的：

// (Compile and link stuff, this part I know works)

// Use the compute shader
Gl.UseProgram(program);

// Create the texture the compute shader will output to
int textureWidth = 512, textureHeight = 512;
uint[] texturesMaking = new uint[1];
Gl.GenTextures(texturesMaking);
uint texture = texturesMaking[0];
Gl.ActiveTexture(Gl.TEXTURE0);
Gl.BindTexture(TextureTarget.Texture2d, texture);
Gl.TextureParameter(Gl.TEXTURE_2D, Gl.TEXTURE_MAG_FILTER, Gl.NEAREST);
Gl.TextureParameter(Gl.TEXTURE_2D, Gl.TEXTURE_MIN_FILTER, Gl.NEAREST);
Gl.TexImage2D(TextureTarget.Texture2d, 0, Gl.RGBA32F, textureWidth, textureHeight, 0, PixelFormat.Rgba, PixelType.Float, IntPtr.Zero);

// Get the shader output variable and set it
int location = Gl.GetUniformLocation(program, "destTex");
Gl.Uniform1(location, texture); 
Gl.BindImageTexture(0, texture, 0, false, 0, Gl.READ_WRITE, Gl.RGBA32F);

// Send off the compute shader to do work, with one group per pixel
//  (I know this is far less than optimal, it was just a debugging thing)
Gl.DispatchCompute((uint)textureWidth, (uint)textureHeight, 1);

// Wait for compute shader to finish
Gl.MemoryBarrier(Gl.SHADER_IMAGE_ACCESS_BARRIER_BIT);

// Looking at the texture, it is black

这是我的计算着色器：

#version 450
layout(local_size_x = 1, local_size_y = 1) in;
layout(rgba32f) uniform image2D destTex;

void main () {
  imageStore (destTex, ivec2(gl_GlobalInvocationID.xy), vec4(1.0, 0.0, 1.0, 1.0));
}

如果我理解正确，我的纹理在着色器运行后应该是紫色/粉红色，但它只是黑色，打印出一些像素的颜色表明所有值也为零。我做错了什么？

Answer 1

问题在于如何告诉着色器使用哪个纹理。

设置的值

int location = Gl.GetUniformLocation(program, "destTex");
Gl.Uniform1(location, texture); 

必须是图像纹理单元（Gl.BindImageTexture 命令的第一个参数），而不是纹理本身。由于您使用的是图像纹理单元 0，因此您还必须将 0 传递给制服：

GLuint unit = 0;
int location = Gl.GetUniformLocation(program, "destTex");
Gl.Uniform1(location, unit); 
Gl.BindImageTexture(unit, texture, 0, false, 0, Gl.READ_WRITE, Gl.RGBA32F);