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Simple Non-Photorealistic Methods for Animation
(Joel):
Smoke Streams
| In order to simulate smoke, it was
important to create a model that used as few controls as possible, in
order to keep the process simple. The model I developed consists of
one or more smoke streams. Each smoke stream is modeled as a sequence
of points in the stream. Each point is represented by a position (in
3-space, x,y,z) and the amount of time the point has existed (t). This
time factor is normally measured in frames. Though similar to particle
system approaches to simulating smoke, this method uses far fewer
points and therefore reduces the amount of computation required. T.
McReynolds et al use a similar technique for vapor trails, replacing
these “points” with OpenGL billboards. In order to render each smoke
stream, the stream’s points are used as control points for an
interpolated curve, which in turn forms the basis of the given smoke
stream. The number and frequency of these points relate to the degree
of the curve produced. Though these points could be used as control
points for either a Bezier or b-spline curve, I found a simple
sinusoidal curve to be more than adequate. |
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