OpenGL ES 2.0渲染为多种纹理

Question

我正在使用OpenGL ES 2.0构建iPad应用程序。 我需要做的是渲染到多个纹理，然后渲染所有纹理以供查看。 我根据用户触摸位置使用GL_POINTS进行绘制。 我现在拥有的代码是：

生成帧缓冲区，纹理和渲染缓冲区：

glGenFramebuffers(1, &viewFramebuffer);
glGenRenderbuffers(1, &viewRenderbuffer);
glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);

glGenTextures(1, layers);
glBindTexture(GL_TEXTURE_2D, layers[0]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  self.bounds.size.width, self.bounds.size.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[0], 0);

画：

glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
....
glDrawArrays(GL_POINTS, 0, (int)vertexCount);
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER];

上面的工作正常，但是当我想渲染为新纹理时，我的应用程序停止绘制任何新内容。 我绑定这样的新纹理：

glGenTextures(1, &layers[1]);
glBindTexture(GL_TEXTURE_2D, layers[1]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  self.bounds.size.width, self.bounds.size.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[1], 0);

然后再次调用绘图方法。 当渲染到第一个纹理时，我的代码有效，但是当我尝试生成要渲染到的新纹理时，应用程序停止绘制。 有人可以帮忙吗？

Answer 1

我有我的代码可以工作。 我的frameBuffers无法正确生成并且纹理无法正确绑定，因此遇到了几个问题。 经验教训-生成后始终检查frameBuffer的状态！ 这里是：

设置frameBuffers：

// Generate textureFrameBuffer for handling drawing to textures
glGenFramebuffers(1, &textureFrameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);

// Generate renderBufferer for drawing to screen
glGenRenderbuffers(1, &viewRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
[context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(id<EAGLDrawable>)self.layer];
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWidth);
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);

//Generate first texture and bind to textureFrameBuffer
glGenTextures(1, &layers[0]);
glBindTexture(GL_TEXTURE_2D, layers[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  backingWidth, backingHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[0], 0);

//check if frameBuffer is OK
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE){
    NSLog(@"failed to make complete framebuffer objects %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
    return NO;
}

//Generate viewFrameBuffer for drawing to view
glGenFramebuffers(1, &viewFramebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, viewRenderbuffer);

if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
    NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
}

要绘制到第一个纹理：

glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[0], 0);
....
glDrawArrays(GL_POINTS, 0, (int)vertexCount);

生成并绑定第二个纹理：

glGenTextures(1, &layers[1]);
glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);
glBindTexture(GL_TEXTURE_2D, layers[1]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,  backingWidth, backingHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[1], 0);  

绘制到第二个纹理：

glBindFramebuffer(GL_FRAMEBUFFER, textureFrameBuffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, layers[1], 0);
....
glDrawArrays(GL_POINTS, 0, (int)vertexCount);

要将所有纹理绘制到屏幕上：

// Bind view buffer
glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);
//clear screen every frame
glClear(GL_COLOR_BUFFER_BIT);
//bind layer texture
for (int i=0; i<= layerCount; i++) {
    glBindTexture(GL_TEXTURE_2D, layers [i]);
    ....
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

[context presentRenderbuffer:viewFramebuffer];