Rendering to multiple textures

To render to multiple textures, you still use the glDrawBuffers function. However, you use the enums from GL_EXT_framebuffer_object.

Example:

GLenum buffers[] = { GL_COLOR_ATTACHMENT0_EXT, GL_COLOR_ATTACHMENT1_EXT };
glDrawBuffers(2, buffers);

If a framebuffer object is bound with textures attached to GL_COLOR_ATTACHMENT0_EXT and GL_COLOR_ATTACHMENT1_EXT, they will both be rendered to now.

Render to Texture

OpenGL supports fast crossplatform offscreen rendering through the GL_EXT_framebuffer_object extension.

To render to a texture using the framebuffer object you must

1) Create a framebuffer object
glGenFramebuffersEXT(1, &myFBO);

2) Bind the framebuffer object
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, myFBO);

3) Attach a texture to the FBO
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, myTexture, 0);

4) If you need depth testing, create and attach a depth renderbuffer

// Gen renderbuffer
glGenRenderbuffersEXT(1, &myRB);

// Bind renderbuffer
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, myRB);

// Init as a depth buffer
glRenderbufferStorageEXT( GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, width, height);

// Attach to the FBO for depth
glFramebufferRenderbufferEXT( GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, myRB);

5) Render just like you normally would.

6) Unbind the FBO (and renderbuffer if necessary). glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, 0);

7) Use the texture you rendered to!

NOTES:

All textures and renderbuffers attached to the framebuffer object must have the same dimensions.

You must use the GL_EXT_packed_depth_stencil extension to use stencil testing with framebuffer objects.

You can only render to RGB, RGBA, and depth textures using framebuffer objects.


References:

Framebuffer object specification