Question

我想将我的自定义帧缓冲区的颜色附件放入计算机着色器中，以进行简单的图像处理，但是我只得到了黑屏。这是我的示例代码

创建颜色附件

glGenFramebuffers(1, &this->fbo);
glBindFramebuffer(GL_FRAMEBUFFER, this->fbo);
glGenTextures(1, &this->textureColorBuffer);
glBindTexture(GL_TEXTURE_2D, this->textureColorBuffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, this->width(), this->height(), 0, 
GL_RGB, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 
this->textureColorBuffer, 0);

编译和链接着色器

cshader = glCreateShader(GL_COMPUTE_SHADER);
const char *csSrc[] = {
    "#version 440\n",
    "layout (binding = 0, rgba32f) uniform image2D destTex;\
     layout (binding = 1, rgba32f) uniform image2D sourceTex;\
     layout (local_size_x = 16, local_size_y = 16, local_size_z = 1) in;\
     void main() {\              
            vec4 texel;\
            ivec2 storePos = ivec2(gl_GlobalInvocationID.xy);\
            texel = imageLoad(sourceTex, storePos);\
            texel = vec4(1.0) - texel;\
            imageStore(destTex, storePos, texel);\
    }"
};
glShaderSource(cshader, 2, csSrc, NULL);
glCompileShader(cshader);


cshaderprogram = glCreateProgram();
glAttachShader(cshaderprogram, cshader);
glLinkProgram(cshaderprogram);

调用Shader并将纹理绘制到四边形。该着色器是一种简单的颜色切换着色器，用于测试。

glUseProgram(cshaderprogram);
glUniform1i(0, 0);
glActiveTexture(GL_TEXTURE0);
glBindImageTexture(0, outputTexture, 0, GL_FALSE, 0, GL_WRITE_ONLY, 
GL_RGBA32F);


glActiveTexture(GL_TEXTURE1);
glBindImageTexture(0, textureColorBuffer, 0, GL_FALSE, 0, GL_READ_ONLY, 
GL_RGBA32F);
glUniform1i(1, 1);
glDispatchCompute(width() / 16, height() / 16, 1);

glMemoryBarrier(GL_SHADER_STORAGE_BARRIER_BIT);
screenProgram.bind();
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindVertexArray(screenVao);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, outputTexture);
glDrawArrays(GL_TRIANGLES, 0, 6);

我能够正确地将textureColorBuffer渲染为四边形，并且可以写入纹理。我认为我不知道如何从帧缓冲区读取问题。

希望您能帮助我。如果还有问题，请问。

Answer 1

sourceTex的绑定点是1而不是0：

layout (binding = 1, rgba32f) uniform image2D sourceTex;

所以您必须将纹理绑定到图像单元1

glBindImageTexture( 1, // <------- 1 instead of 0
    textureColorBuffer, 0, GL_FALSE, 0, GL_READ_ONLY, GL_RGBA32F);

请注意，Images units和Texture units是不同的东西。

当然，您也可以在渐变着色器中使用均匀的纹理采样器。如果destTex和sourceTex的大小相同，则可以将texelFetch与gl_GlobalInvocationID一起使用，以查找sourceTex：

layout (local_size_x = 16, local_size_y = 16, local_size_z = 1) in;

layout (binding = 0, rgba32f) uniform image2D destTex;
layout (binding = 0) uniform sampler2D sourceTex; 

void main()
{       
    ivec2 pos = ivec2(gl_GlobalInvocationID.xy);       

    vec4 texel = texelFetch(sourceTex, pos, 0);

    texel = vec4(1.0) - texel;
    imageStore(destTex, pos, texel);
}

在上面的代码段中，图像单元0用于destTex，纹理单元0用于sourceTex。

顺便说一句，您确定要这么做

texel = vec4(1.0) - texel;

请注意，如果texel的alpha通道为1.0，它将完全透明。

OpenGL帧缓冲ColorAttachment计算着色器

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