OpenGL source code

"the GL class"???  What GL class?

OpenGL is generally implemented as closed-source by the video-card driver companies on Windows, by Apple on Mac, and varied implementations under linux (some by vendor, some abstracted using the open-source Mesa GL replacement).  Hardware acceleration generally needs some kind of exposed 'hooks' to the video card, thus the card companies are involved.

Thus, aside from getting the source to Mesa, or GLUT, or the above-mentioned OpenGL sample implementation that SGI distributes, you can't actually GET the sources to the OpenGL implementations for the average say Windows graphics card...

-d

well:
- use fixedpoint z
- use w-buffer (linear)
- use other optimizations in calcs (do a line at a time, cache-align stuff like 64-bytes)
- test Z before any other work
- do zone rendering (see PowerVR or intel), does small chunks, better cache-hits, better ability to quick-eliminate things from contention
- render front-to-back (z test fails more often, more quickly)

... etc.

What IS it you are trying to do?

Also can look at span-buffering, S-buffering, as another painter-type approach.

-d

yowch.  yeah, java has proven difficult for software 3d... the folks who pull it off have probably used approaches more towards painters or span-buffering (with bsp trees, you can get somewhat decent results... never as accurate as a z-buf, but...), and most certainly take every shortcut they can to throw out large pieces of geometry before per-pixel computations.  frankly, that's what I think span-buffering and the zone-based-zbuffering (PowerVR, intel) try to do by looking at smaller pieces of geometry, hoping to make higher-level decisions to spare low-level, expensive, computation.  that includes general stuff like backface culling...

thus, the Java3D, Jogl, etc. libraries have really taken off as they give access to hardware or core-optimized routines.

I believe s-buffering (from old, old memory) was the basic Quake engine approach.  BSPs were used to optimize and cull at a high level, and s-buffering then worked off the edges of the polys, trying to pre-determine what span-lines of a given poly were 'in front'.  Which, in essence, is just a further improved version of painters. ;)

Here's the quickie s-buffer resources I found:
http://www.xs4all.nl/~smit/sbuffer.txt
http://www.flipcode.com/articles/article_cbuffer.shtml

Stuff by Michael Abrash is also always good... for obvious reasons (quake..).
http://www.gamers.org/dEngine/quake/papers/ddjzsort.html

That's all I've got at this point.  There's always 'smarter not harder' approaches to rendering, but none of it is snap-your-fingers instantaneous.  The Quake stuff might be the best reference, but it's also fairly complex code. ;)

-d

This is the best pure java 3d engine I know of..

http://www.idx3d.ch/idx3d/idx3d.html

maybe it can help?  (there is source available)