A Real-time Beam Tracer with Application to Exact Soft Shadows

A Real-time Beam Tracer with Application to Exact Soft Shadows
Ryan Overbeck, Ravi Ramamoorthi, and William R. Mark,
Eurographics Symposium on Rendering, 2007.


This paper presents CPU realtime beam tracing method based on clipping(yeah, it is idential to Sutherland clipper used in traditional polygon rasterizer).

The method is much faster than previous beam like raytracing which is capable of soft shadow calculation.

Spatial structures used in this beam tracer is kd-tree, but I think it could be easily adapted to use BVH or grid.

Advantage of present beam tracer.

– Fast raytracing on flat surface.
– Exact soft shadow(no monte carlo noise for area light!)
– Naturally calculates derivative(ray differentials)

Disadvantage of present beam tracer.

– Slower raytracing for highly complexed scenes(e.g. polygon is smaller than pixel)

For now, beam tracer’s disadvantage is critical for offline massive rendering.
But I think once any more better spatial structures/traverser for beam tracing is found,
beam tracing might be widely used for CPU online/ofline raytracing.

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