OpenGL ES运行多个着色器

Question

基于前面的问题，我一直在研究如何在一次传递中运行多个着色器（即，有一个FBO并渲染为纹理）。这是Iphone上的OpenGLES 2。

我创建了一些代码，但只运行一帧。所以显然我做错了什么，但我无法发现它。

输入数据是摄像机的核心视频缓冲区。

任何指针或修复程序都非常欢迎:)。

感谢，

西蒙

PS：我已经把一切都变成一个方法现在 - 只是这样我可以简单地专注于得到它的工作！

- (void) PingPong:(CVImageBufferRef)cameraframe; 
{ 
int bufferHeight = CVPixelBufferGetHeight(cameraframe); 

int bufferWidth = CVPixelBufferGetWidth(cameraframe); 

// Build the first FBO - this is wasteful - don't do this everytime 
GLuint firstFBO; 
glGenFramebuffers(1, &firstFBO); 
glBindFramebuffer(GL_FRAMEBUFFER, firstFBO); 

// Build the first texture and copy the video stuff into it 
GLuint sourcetexture; 
glGenTextures(1, &sourcetexture); 
glBindTexture(GL_TEXTURE_2D, sourcetexture); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); 


// Build the second texture 
GLuint nextTexture; 
glGenTextures(1, &nextTexture); 
glBindTexture(GL_TEXTURE_2D, nextTexture); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); 

// Attach the texture to our first FBO 
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, sourcetexture, 0); 


// Using BGRA extension to pull in video frame data directly 
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bufferWidth, bufferHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(cameraframe)); 

//glDrawBuffer(sourcetexture); 
glEnable(GL_TEXTURE_2D); 
glViewport(0, 0, backingWidth, backingHeight); 
glBindTexture(GL_TEXTURE_2D, sourcetexture); 
glUseProgram(greyscaleProgram); 

// Now do the 2nd pass using the sourcetexture as input 
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, nextTexture, 0); 
glBindTexture(GL_TEXTURE_2D, nextTexture); 
glUseProgram(program); 

// Present the framebuffer to the render buffer 
[EAGLContext setCurrentContext:context]; 

glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer); 

[context presentRenderbuffer:GL_RENDERBUFFER]; 

// Clean up stuff 
glDeleteTextures(1, &sourcetexture); 
glDeleteTextures(1, &nextTexture); 

}

Answer 1

哪里是你画的代码？绘图是触发着色器执行的原因，而我现在看到它的代码有零绘制调用（glDrawArrays，glDrawElements等），所以它不工作，因为你没有绘制。

绘制一个全屏幕四元组来触发每个过程的着色器执行，它将起作用。

此外，建议使用glCheckFramebufferStatus检查您的FBO配置是否受支持，并且可以在您的GL实施中使用。