OpenGL 帧缓冲区 ColorAttachment 到计算着色器

Question

我想将自定义帧缓冲区的颜色附件放入计算着色器中以进行简单的图像处理，但我只得到黑屏。这是我的示例代码

正在创建颜色附件

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);

调用着色器并绘制纹理到四边形。着色器是一个简单的颜色切换着色器，用于测试目的。

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 渲染到四边形并且我可以写入纹理。我认为我不知道如何从帧缓冲区读取的问题。

希望你能帮助我。如果仍有问题，请提出。

Answer 1

sourceTex的绑定点是1不是0:

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

所以你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);

注意，Images units and Texture units 是不同的东西。

当然你也可以在计算着色器中使用统一的纹理采样器。如果 destTex 和 sourceTex 的大小相同，则可以使用 texelFetch 和 gl_GlobalInvocationID 来查找 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);
}

在上面的代码片段中，destTex 使用了图像单元 0，sourceTex 使用了纹理单元 0。

顺便问一下，你确定要这样做吗

texel = vec4(1.0) - texel;

注意，如果texel的alpha通道为1.0，会变得完全透明

OpenGL 帧缓冲区 ColorAttachment 到计算着色器

OpenGL Framebuffer ColorAttachment to Compute Shader

c++

opengl

shader

framebuffer

glsl