VRML documentation

## Summary of recent changes:

(see ChangeLog file for details)

#### Version 3.2.4 -> 3.3 (August, 23 2001)

- XRML: new input file format, based on VRML'97 with extensions for physically based materials: lot's of reflection models, non diffuse light sources, textures (2d,3d, procedural,...), bump mapping, high dynamic range environment mapping, ...
- serious photon mapping improvements and new features
- experimental path differential support in stochastic ray tracing
- POOLS memory management library deprecated
- various minor changes, bug fixes and code clean-ups

#### Version 3.2.3 -> 3.2.4 (December 15, 2000)

- photon map bug fix + minor fixes

#### Version 3.2.2 -> 3.2.3 (November 30, 2000)

- Radiance pic file format exporter (new)
- better test pattern for gamma correction + new test pattern for setting monitor black level
- lot's of internal changes (ray hit records, shader interface, ray tracing debugging aids) concerning texturing support.
- density estimation is out of order.

#### Version 3.2.1 -> 3.2.2 (November 7. 2000)

- memory management routines re-implemented
- gamma correction improvements + test image for interactive setting appropriate gamma
- 63-bit Niederreiter sampling in stochastic Jacobi radiosity solves rare overflow error

#### Version 3.2 -> 3.2.1 (October 30. 2000)

- OpenGL rendering accelerations: sorted rendering (large to small, front to back) + viewing frustum culling for large building models (we tested a 1Mpoly model)
- minor features, fixes and code clean-ups including off-screen rendering fix for recent Mesa libraries, large memory usage (>0.5 GB on Linux + >2GB on SGI Onyx2, with 64-bit ABI), global line tracing engine, photon map crash fix, ...

#### Version 3.0 -> 3.2 (August 28, 2000)

- new Photon Map rendering method (Frank Suykens)
- improved and extended stochastic ray tracing and bi-directional path tracing (Frank Suykens)
- complete re-implementation of Monte Carlo radiosity algorithms as described in Philippe Bekaert's PhD thesis, replaces old stochastic ray and WDRS radiosity
- new tone mapping methods (Jan Prikryl) + calibrated monitor support
- validation: different rendering methods now yield consistent results, also consistent with Radiance rendering system
- numerous internal changes and bug fixes