Interval Ray Tracing in Computer Graphics

[David G. Hough on validgh]

The latest SIGNUM newsletter contains the abstract for the following thesis
which applies interval methods to ray tracing - an area new to me.

Ph. D. Thesis of Wolfgang Enger at Freiburg, neumasun1.ruf.uni-freiburg.de,
in German:

Interval Ray Tracing - a Divide and Conquer Strategy for realistic
Computer Graphics

Using interval arithmetic to solve the equations for intersections of
ray bundles with a parametric surface, the surface is adaptively subdivided
into pieces which can be drawn with (nearly) constant intensity.  The
method was tested with scenes of 9-21 objects defined by B-spline surfaces.
On pictures with 16 different intensities and a resolution of 640x480
pixels, the speed-up factor over a traditional ray tracing method was
2.5-3.1.  Since coherence is preserved, a very simple dithering scheme
suffices for smooth transitions between adjacent intensities.  Reflection
and refraction effects are included.