From Explore to Maya...

IPR (the Interactive Photorealistic Renderer) was the renderer in the
TDI (Thompson Digital Image) Explore product line.  TDI was acquired by
its former competitor Wavefront Technologies several years ago, becoming
Wavefront | TDI, and continued to sell both their 3D products.  Then
Wavefront | TDI was acquired by SGI along with former competitor Alias
Research, forming Alias | Wavefront (with TDI no longer mentioned in the
company name.)

The render quality of IPR was indeed very good, although I don't know
that it was ahead of where Mental Ray is today.  The "Interactive"
concept - being able to interactively adjust the rendering including
raytracing and shadows - was very useful, and will be emulated shortly
by Softimage's Twister.

Alias | Wavefront has merged and cannibalized the best features of all
three product lines (Alias Research's Alias Power Animator, Wavefront's
original Advanced Visualizer products, Dynamation, and Kinamation, and
TDI's Explore with 3Design and IPR) as the starting point for their new
Maya system.  IPR emerged as the main "guts" of the new Maya renderer,
which says a lot about its quality, to win in a best-of-the-best merger
like that (although the shaders and particle rendering from Alias Power
Animator were also used in the Maya renderer.)

Now that the old products are being phased out in favor of Maya, most of
the Explore, 3Design, and IPR screenshots and details seem to have been
taken off of the web page.  Most of IPR has already been adapted into
the Maya renderer, and owners with support were given a free upgrade to
Maya.  You can see http://www.aw.sgi.com for some info, and a .pdf file
with info about IPR, but most of the new renderings are from IPR's
grandson, the Maya renderer.

-- Jeremy Birn
-- http://www.3drender.com/
--
-- "Secrets of Softimage 3D" videos:
-- http://www.3drender.com/softimage/secrets.html