Converting glReadBuffer() / glDrawBuffer() calls into OpenGL ES

Question

I'm having trouble understanding how to port glReadBuffer() & glDrawBuffer() calls into Open GL ES 1.1. Various forum posts on the internet just say "use VBOs," without going into more depth.

Can you please help me understand an appropriate conversion? Say I have:

glReadBuffer(GL_FRONT);

followed by

glDrawBuffer(GL_BACK_LEFT);
state->paint(state_id, f);

How can I write the pixels out?

Answer 1

glReadBuffer and glDrawBuffer just set the source and target for subsequent drawing operations. Assuming you're targeting a monoscopic device, such as the iPhone or an Android device, and have requested two buffers then you're already set for drawing to the back buffer. The only means of reading the colour buffer in GL ES is glReadPixels, which will read from the same buffer that you're drawing to.

All of these are completely unrelated to VBOs, which pass off management of arrays of data to the driver, often implicitly allowing them to be put into the GPU's direct address space.