Friday, April 10, 2009 | Permalink
In my framework work I've started adding OpenGL 3.x support. I was one of the angry voices about what happened with OpenGL 3.0 when it was released. It just didn't live up to what had been promised, in addition to being a whole year too late. While OpenGL 3.0 didn't clean up any of the legacy crap, OpenGL 3.1 finally does. A bunch of old garbage that were simply labelled deprecated in 3.0 have now actually been removed from OpenGL 3.1. As it looks now, OpenGL is on the right track, the question is just whether it can make up for lost time and keep up with Direct3D going forward.
However, along with the OpenGL 3.1 specification they also came up with the horrible GL_ARB_compatibility extension. I don't know what substance they were under the influence of while coming up with this brilliant idea. Basically this extension brings back all legacy crap that we finally got rid of.
This extension really should not exist. Please IHVs, I urge you to NOT implement it. Please don't. Or at the very least don't ship drivers with it enabled by default. If you're creating a 3.1 context, you're making a conscious decision not to use any of the legacy crap. Really, before venturing into OpenGL 3.1 land, you should've made the full transition to OpenGL 3.0. Fine, if a developer for some reason still needs legacy garbage during a transitional period while porting over the code to 3.1 he can enable it via a registry key or an IHV provided tool. But if you're shipping drivers with it enabled by default, you know what's going to happen. An important game or application is going to ship requiring the support of this extension, and all the work done on cleaning up the OpenGL API is going to be wasted. It would have to be supported forever and we're back at square one.
In my framework I'm going to use the WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB flag. This means that all legacy crap will be disabled. For instance calling glBegin()/glEnd() will be a nop. This will ensure that I'm sticking to modern rendering techniques. All new code should be using this. The only reason for not using it is if you're porting over some legacy code. The deprecation model that OpenGL 3.0 added is fundamentally good. It allows us to clean up the API while giving developers the ability upgrade their code. If done right the whole OpenGL ecosystem would modernize by necessity. This of course relies on Khronos not to poop all over the efforts with stuff like GL_ARB_compatibility.
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| Last comment by Anon (2009-04-13 18:12:15)