Simple OpenGL ES 2.0 question. If I need to have depth and color buffer, do I have to render geometry twice? Or I can just bind/attach depth buffer while render color frame?
Or I need MRT/render twice for this?
It's the normal mode of operation for OpenGL to updated both the color and depth buffer during rendering, as long as both of them exist and are enabled.
If you're rendering to an FBO, and want to use a depth buffer, you need to attach either a color texture or a color renderbuffer to GL_COLOR_ATTACHMENT0, by calling glFramebufferTexture2D() or glFramebufferRenderbuffer() respectively. Then allocate a depth renderbuffer with glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, ...), and attach it to GL_DEPTH_ATTACHMENT by calling glFramebufferRenderbuffer().
After that, you can render once, and both your color and depth buffers will have been updated.