OpenGL Framebuffer ColorAttachment to Compute Shader

本文关键字：Compute Shader to ColorAttachment Framebuffer OpenGL 更新时间：2023-10-16

我想将自定义帧缓冲的颜色附件放入计算着色器中进行简单的图像处理，但我只得到黑屏。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 440n",
"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);

调用着色器并将纹理绘制为四边形。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。

我希望你能帮助我。如果还有一些问题，请问。

sourceTex的绑定点是 1 而不是 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);

请注意，图像单位和纹理单位是不同的东西。

当然，您也可以在coumpute着色器中使用纹理采样器制服。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);
}

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

顺便问一下，你确定要做吗

texel = vec4(1.0) - texel;

请注意，如果texel的 alpha 通道为 1.0，它将变得完全透明。