title: OpenGL: How to update only a portion of a texture?
body: <p>I dont want to update the whole texture every time i change a small part of it, what is the command for this?</p>
  
  <p>And when i have mipmapping on, set with GL_GENERATE_MIPMAP, how optimized is that internally? will it calculate whole image again, or just the part i updated?</p>