我正在尝试编写GPGPU程序,只需将纹理的内容复制到附加到FBO的输出纹理即可。但是,我看到输入纹理数据未正确加载或绑定。我不明白出了什么问题。
这是我的代码:
void render()
{
int i;
float * result, *in;
//allocating and filling data in the input texture
result = (float * ) malloc(4*32*32*sizeof(float));
in = (float *) malloc(4*32*32*sizeof(float));
for(i=0;i<32*32*4; i++)
{
in[i]=1.0f;
}
makeBuffers(); //makes the vertex and element buffers
makeTexture(in); //makes the input textures
makeShaders(); //makes the vertex n pixel shaders
makeProgram(); //makes the program
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBindBuffer(GL_ARRAY_BUFFER, res.vertexBuffer);
glVertexAttribPointer(res.position, 2, GL_FLOAT, GL_FALSE, sizeof(GLfloat)*2, (void*)0);
glEnableVertexAttribArray(res.position);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, res.elementBuffer);
res.texture= glGetUniformLocation(res.shaderProgram, "intexture");
/* bind texture */
makefbo(); // making the offscreen frame buffer object
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, res.texture);
glUniform1i(res.texture, 0);
glDrawElements(GL_TRIANGLE_STRIP,4, GL_UNSIGNED_SHORT, (void*)0);
// glFlush(); // i think drawing would be enough now.
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT); //reading back data from the framebuffer
glReadPixels(0, 0, 32, 32,GL_RGBA,GL_FLOAT,result);
printf(" float values n");
for(i=0; i< 32*4 ; i++)
printf(" %f ", result[i]);
printf(" n");
}
这是我的maketexture()函数
glGenTextures (1, &res.texture);
glBindTexture(GL_TEXTURE_2D,res.texture);
// set texture parameters
glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D,
GL_TEXTURE_WRAP_T, GL_CLAMP);
// define texture with floating point format
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA32F,
texSize,texSize,0,GL_RGBA,GL_FLOAT,0);
// transfer data to texture
glTexSubImage2D(GL_TEXTURE_2D,0,0,0,texSize,texSize,
GL_RGBA,GL_FLOAT,data);
这是我的帧缓冲对象准备和输出纹理绑定:
glGenFramebuffers(1, &res.fbo);
glBindFramebuffer(GL_FRAMEBUFFER, res.fbo);
glViewport(0, 0, 32, 32);
glGenTextures(1, &res.tex);
glBindTexture(GL_TEXTURE_2D, res.fbo);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F,
32, 32, 0, GL_RGBA, GL_FLOAT, 0);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D, res.tex, 0);
数据似乎未正确读取。我尝试将输入纹理附加到帧缓冲对象,并尝试立即读回纹理数据,然后数据显示正常。但是,当我尝试渲染到屏幕外纹理时,它没有给出正确的输出。它在像素着色器执行结束时只给出一堆零。
像素着色器采用输入纹理并将数据复制到输出纹理中:outColor = texture2D (intexture, texcoord);
有人认为这有什么问题吗?
您的代码缺少很多上下文,但我的印象是,您只绑定一次所有内容,然后就这样保留了它。这不是它的使用方式,并且可能无法正常工作。
基本要点是,如果将纹理用作 FBO 渲染目标,则不得将其用作采样源。因此,您必须根据需要取消绑定纹理/FBO,这样事情就不会相互踩踏,或者您正在加载着色器,这些着色器只是禁止纹理访问。恕我直言,取消绑定是更简单的选择(但是在 OpenGL-4.4 中发布了无绑定纹理扩展,它可能成为 4.5 的核心)。