William Pokorny <pokorny_epix_net> wrote:
> http://www.tomshardware.com/reviews/ray-tracing-rasterization,2351.html

"To create soft shadows or diffuse reflections (like those you see in
brushed metal, for example), more advanced ray tracing techniques like
path tracing or distributed ray tracing are needed. But such
techniques require a much greater number of rays and are still far
from being feasible in real time."

  Actually "sending more rays" to simulate volumetric rays (which is
basically what those techniques are trying to achieve) is not the only
way.

  AFAIK Pixar used true volumetric raytracing in Cars, rather than classic
raytracing. In other words, rather than shooting rays (which are infinitely
thin lines), they shoot cones. Then they calculate the intersection of these
cones with the scenery/lights. These intersection calculations return the
percentage of how much the cone covers the tested polygon, which allows for
easy blurred reflections, shadows and other similar effects. The number of
"rays" remains the same.

  Of course the problem is that calculating the intersection of a ray and
an object is relatively simple, but calculating the intersection of a cone
and an object (so that you can calculate how many % is covered) is very
complicated. It simplifies things when you only have to do cone-triangle
intersections (basically you only have to calculate how many % of the
triangle resides inside the cone), but still.

-- 
                                                          - Warp

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