OpenGL in REALbasic Part 1 by Seth Willits 11-12-04 Printer Version

OpenGL in REALbasic
First, let me just a few things: We won't be implementing Doom 3 in REALbasic through these articles. In fact, if you were looking for anything really cool and fantastic, well, this article surely isn't that, but some later tutorials might be a little more interesting we're going to start off slow, very slow. These articles won't be teaching you OpenGL either, we're only going to touch on how to use OpenGL in REALbasic based on my (few) experiences.

First things first, (or rather second things second since I already did something first) we should all thank Asher Dunn from Fireye Software for writing the spectacularly awesome OpenGL Declare Library. I can't imagine how many hours it took him to do it, but I know the REALbasic community owes him many many thank you's.

If you don't know OpenGL but want to learn it, see the NeHe tutorials. You should be able to do the first few tutorials without any problem using the project from this article.

OpenGL Declare Library
Alright, so what is the OpenGL Declare Library? It's a set of modules that wrap hundreds of constants and functions in OpenGL, GLUT, AppleGL, WindowsGL, and even a few from Display Manger which allow REALbasic developers to use OpenGL directly in REALbasic applications. What does this mean? If you like the idea of 3d in REALbasic but are horrified by having to carry around the Quesa library with your application or turned off by its speed (or lack thereof) relative to how other applications feel, then using OpenGL directly gives you all the flexibility you'd ever need, and nothing left to complain about!

Above we see that the first thing done is creating a pixel format. Below you can see that we fill a memory block with flags describing the pixel format we want to create, then we select the pixel format using aglChoosePixelFormat. Normally these flags are sent as an array to aglChoosePixelFormat but we can't do that with REALbasic so we use a memory block on pass a pointer to it, which is all passing an array really does. If you're not familiar with how all of this setup is done, there are a couple places on the net that will explain it better than I am here. Namely, try the #idevgames IRC room and ask, visit the iDevGames website, possibly the mac-games-dev mailing list... there are numerous places to go.

If the pixel format isn't selected properly, we bail out of the SetupContext method by returning false which prevents anything from being rendered later on. If it is, the context is created and then we attach it to a window by using aglSetDrawable. The MacGetWindowPort method takes a REALbasic Window and returns the window's port (it's a low level Window Manager thing). Passing it to aglSetDrawable tells the links the context to the window. aglSetCurrentContext selects the context so that any calls to OpenGL work with that context and not any other and then we do some stuff that you don't need to concern yourself with.

The Animation
Again, I'm not really trying to teach you this stuff, I just want to show it to you. Learning it is a whole other story that I'm not up to writing. Ok, so the interesting part is running the animation. In OpenGLView this is done using the Run method. The Run method runs a tight loop that does some of the standard things that are required or usually done before animating and during every frame. In a nutshell, it's all the tedious stuff no one likes doing. Towards the bottom of the method however, right before we swap the buffers, we call the Render event of the OpenGLView and pass a fractional value in seconds which is the time since the last call to the Render event. This bit of "coolness" simply lets you drag and drop an OpenGLView onto a window and start coding the actual object drawing code, kind of like an NSOpenGLView in Cocoa.