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spenca
08-26-2003, 06:41 AM
Hey everyone! New to Open GL, and I'm supposed to port a GL program to Open GL. I can find plenty on Open GL, but am having trouble with locating tutorials/books on GL. Can anyone please direct me to the right source? Books would be preferable. Thanks!

harsman
08-26-2003, 06:52 AM
IrisGL to OpenGL mapping (http://www.opengl.org/developers/documentation/white_papers/irisgl2opengl.txt)
How OpenGL differs from IrisGL (http://www.opengl.org/developers/documentation/white_papers/ogl_vs_igl.html)

Amazingly enough, those can be found right on this site under Developers->Documentation->White papers.

[This message has been edited by harsman (edited 08-26-2003).]

dorbie
08-27-2003, 12:34 AM
FYI - There was a script that did a lot of this on sgi systems that would leave comments around the non portable stuff.

The biggest most common differences are:

The lack of windowing and event handling so in IrisGL the winopen() and qdev() stuff & all related functions has to be replaced with platform specific code like X11 calls or Windows calls.

Then there's the def & bind semantics in Iris GL that don't exist in OpenGL (except textures added in OpenGL 1.1 for texture objects). Materials, lights, texture environments are all graphics resources to be bound with handles in IrisGL, instead of the incremental changes supported by OpenGL. The philosophy was to use display lists in OpenGL for this stuff, that stuck with everything except textures.

There is a book like guide on this, if you install the right documentation options on an sgi it will appear on your insight bookshelf (I think that's what it's called):

"IRISGL to OpenGL Porting Guide" (PostSctipt tar file)
http://www.tnt.uni-hannover.de/js/soft/compgraph/ps/PortGuide.ps.tar

Won
08-27-2003, 04:21 AM
Does GL means IrisGL? There's this other graphics library called just "GL" that (I think) was used in some older military simulations, but aside from that I don't know anything more about it, unfortunately...

-Won

dorbie
08-27-2003, 09:27 AM
GL probably refers to IRIS GL. Anything before the Infinite Reality and Indigo2 IMPACT used IRIS GL natively. Reality Engine 2 had OpenGL support added after release but IRIS GL was still preferred on those platforms.

After OpenGL hardware arrived IRIS GL support was maintained on newer hardware by igloo (acronym for "iris gl on opengl") a wrapper/portability library on top of OpenGL.

GL or IRIS GL was not exclusive to military simulators, although that's where I used it, ALL 3D graphics on SGI systems used IRIS GL prior to Infinite Reality & IMPACT graphics.

Won
08-27-2003, 11:26 AM
You're right. I dug out the old paper I remembered it from. I must've confused it with IGL or something.

-Won

spenca
08-27-2003, 03:58 PM
Ah, yes. I think I do mean Iris GL. I was told it was just GL. Thanks everyone!