OpenGL ES can't render to texture - c++

Question

I wrote this code:
First, I generate a texture and a depth buffer, then bind them to a framebuffer.
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
GLint max;
glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE,&max);;
if(max<=esContext->width||max<=esContext->height)
{
printf("Too big!\n");
getchar();
}
glGenFramebuffers(1,&framebuffer1);
glGenTextures(1,&texturel);
glBindTexture(GL_TEXTURE_2D,texturel);
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA,esContext->width,esContext->height,0,GL_RGBA,GL_UNSIGNED_BYTE,NULL);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glGenRenderbuffers(1,&depthbuffer);
glBindRenderbuffer(GL_RENDERBUFFER,depthbuffer);
glRenderbufferStorage(GL_RENDERBUFFER,GL_DEPTH_COMPONENT24,esContext->width,esContext->height);
glGenRenderbuffers(2,renderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER,renderbuffer[0]);
glRenderbufferStorage(GL_RENDERBUFFER,GL_RGBA8,esContext->width,esContext->height);
glBindFramebuffer(GL_FRAMEBUFFER,framebuffer1);
glFramebufferTexture2D(GL_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D,texturel,0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER,GL_DEPTH_ATTACHMENT,GL_RENDERBUFFER,depthbuffer);
Then I render a box to the framebuffer and try to render the texture to my screen:
glBindFramebuffer(GL_FRAMEBUFFER,framebuffer1);
glViewport(0,0,esContext->width,esContext->height);
glClearColor(1.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
g_renderer->draw_box(&s);
glBindFramebuffer(GL_FRAMEBUFFER,0);
glClearColor(1.0,1.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
g_renderer->render(texturel,0,0,esContext->width/2,esContext->height/2);
eglSwapBuffers( esContext->eglDisplay, esContext->eglSurface );
At the end, the result looks like random data.
I have tried many ways to render to texture, even copying the code in the OpenGL ES books, but the result is still wrong.

Answer 1

Assuming that you're using ES 2.0, the formats you are using for your texture and renderbuffer are not valid for render targets.
In ES 2.0, the only depth format that is valid for render targets is DEPTH_COMPONENT16.
For color render targets, the only valid formats are RGBA4, RGB5_A1, and RGB565.
Therefore, to get this to work with standard ES 2.0, you can for example use:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB,
esContext->width, esContext->height, 0,
GL_RGB, GL_UNSIGNED_SHORT_5_6_5, NULL);
...
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16,
esContext->width, esContext->height);
There are extensions to ES 2.0 to add support for the formats you are trying to use:
OES_rgb8_rgba8 adds support for RGB8 and RGBA8 as a color render target format.
OES_depth24 adds support for DEPTH_COMPONENT24 as a depth render target format.
But you will have to test for the presence of these extensions before attempting to use these formats.
Anytime you have problems with FBO rendering, it's always a good idea to call glCheckFramebufferStatus() to validate that the framebuffer status is valid.