   One framebuffer with multiple textures
  Hello, I have one framebuffer with multiple textures. How can I copy the data from one texture to another, inside the framebuffer? Am I copying inside the GPU so it is fast or I have to use the CPU? Thanks!   
  When you say you have a framebuffer, you mean a FBO? If so, you can copy from one texture to another just by rendering a texture mapped quad. I don't know if any other method exists.   