Rendering for film 2005-05-04 - By Andy Jones
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Some good links:
Anti-aliasing
http://www.lamrug.org/resources/samplestips.html
Motion blur
http://www.lamrug.org/resources/rastips.html
http://www.lamrug.org/resources/motiontips.html
Final gathering and ambient occlusion
http://www.lamrug.org/presentations/mar2005/LAmrUG_March_2005_v2.pdf
General SI rendering bible
http://www.softimage.com/products/proren/media/XSI_rendering_lajoie.pdf
For FG, I think the only concern with append points to file mode is that
your FG map could eventually get very large and slow. Do you have
moving objects? If nothing is moving but the camera, there are a lot of
shortcuts you can do. For example, you could open a render-region and
orbit around your scene, generating FG points, then "freeze" your FG map
with the "generate FG points only if file doesn't exist" option. Keep
in mind, though, that that option is a lie, and MR will still generate
new FG points on surfaces where there are not enough pre-existing FG
points. Freezing the fg map will eliminate a lot of chatter and make it
possible to use lower FG settings without creating noticable artifacts.
If you have moving objects in your scene and they occupy more than a
small portion of the image, a lot of people would describe using FG as
"ambitious," especially if you don't have access to at least a mid-sized
renderfarm. That's not to say it can't be done, though.
One trick for getting away with lower FG settings is to eliminate noise
in the scene. For example, if you have a texture with a lot of detail,
you could use a ray switch node in your material to switch to a blurred
version of the texture if the ray is a final gathering ray. This is
described in the XSI_rendering_lajoie pdf. Falloff also makes a huge
difference in render times, as it won't take as long to trace each FG
ray. Another thing that makes a big difference in FG is MR 3.4, which
supposedly allows you to cut your accuracy in half and get similar
results. But that's obviously not an option in XSI yet -- hopefully soon.
For antialiasing, we often use 0,2 with a threshold of .02. The
threshold is your friend, as it allows you to avoid sampling areas of
the image that don't need it. You can also get a smoother-looking image
by playing with your filter.
Hope this helps.
-Andy
tony@(protected) wrote:
>Thanks for the quick replies guys, very helpful.
>As I said before, I've never done anything for 35mm projection before, as so i
>assumed that because it would be projected onto a large cinema screen, finer
>aliasing levels would be required to ensure good detail.
>
>I did a test at -1/1 and 1/2 and it renders much quicker, although the initial
>FG computation still takes a while. I suppose I'll only know whether the
>quality is acceptable when I do some tests at the film lab.....
>
>Speaking of FG, for the FG Map, I'm again assuming that Append points to file
is
>acceptable as oppsed to generating a new map each frame. The animation is one
>continuous dolly around an object, so there is costant camera motion.
>
>Cheers for your help.
>
>regards
>Tony.
>
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