 | | | Tips and carrara suggestions | Tips and carrara suggestions 2005-03-03 - By proanimation
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Common animation problem : "Sparkling" at a distance
I come back to Carrara every so often to see what has change over
the years. This is one that has always bugged me.
When you move the camera in a scene where textured objects go off
into the distance i.e. a terrain /floor /ground etc you get a
sparkling or random noise effect on the parts of your ground that
are in the distance. The problem is that the texture is too detailed
for something that far away. As long as the camera is stationary and
the ground doesn't move, every thing is fine but when things move a
ray may hit a blue spot on one frame and a white on the next frame
and back to blue on the next etc. What is needed is a way to take
the number of texture pixels that would represent one screen pixel
and average that number of surrounding texture map pixels together.
This is especially noticeable in the bump channel. Depth of field
just makes out-of-focus sparkles. I don't know what adding this pre-
blur would do to rendering times but the work-arounds take a huge
amount of time and ultimately aren't as good as the pre-blur
solution would be.
My work-around is:
For ground type objects, Given one general camera position you can
make one giant texture map and in an image editor, blur the map a
lot on the parts that will be far from the camera, and don't blur
the parts close to the camera. Sometimes I only need to do this with
the bump texture and other times in all texture mapped channels.
For objects that are moving toward or away I use a movie shader that
has the texture map 100% blurred at one end of the movie, and no
blur at the other. This way I can control the amount of blur
depending on the number of pixels the object takes up on the screen.
When the entire object is far enough away to only be represented by
one screen pixel that's the point of 100% blur (the entire texture
map is blurred to one average color).
Having a animatible blur shader opp would work for these moving
objects and would be a lot easier than creating the movies, but I
believe it might add a bit more rendering time over the movies.
The same is true for objects that become smaller than a pixel. When
they move across the screen a ray may or may not hit it thus causing
the sparkle effect and shadows that appear and disappear on random
frames. A way to make sure that an object isn't missed and reducing
its polygon count relative to how many screen pixels it represents
would both speed up rendering (by not needing to use a high object
accuracy), and stop the sparkles.
My workaround to simulate this is by swapping visibility of complex
objects with simpler objects as they move away and represent less
screen space but that's a lot of hand work and has to be re-done for
different angles etc and it's hard to not get a visible jump in the
animation when the swap happens. Turning up the object accuracy
helps with the missed object sparkle but it only helps, and at a
great cost of rendering speed.
Robert Coble
Proanimation@(protected)
(since the first ray dream)
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