title: Render inside of OpenGL scene from an external application using an injected DLL
body: <p>I've been able to inject DLLs in to applications for things like keyboard actions, but how does one hook in to an OpenGL program and draw over it? I've read many "tutorials" and answers, but they all outline the idea behind doing it, not how to actually do it. If someone could point me in the right direction, I'd much appreciate it.</p>
  
  <p>What I intend to do is be able to draw an overlay (or maybe draw into the actual scene? Is that possible?) from a 3rd party application in RAM only (injected dll). My only experience with OpenGL is via GLUT, but I'm willing to learn if need be. </p>
  
  <p>After hours of research, I have found an open-source application that can do what I want, and looked through its code, but can't seem to find what method is being hooked or and how the ASM code is changed at that specific method. </p>
  
  <p>Is the method to be hooked defined when the dll is injected, or does the dll do it upon being attached? From my understanding, you could do either, but is one better than the other? </p>
  
  <p>I'm looking for a comprehensive tutorial, or a simple example of such a thing. If someone could point me in the right direction, that'd be great!</p>