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Topic: Direct Computation GI: The Real Deal

posted by Vladimir Koylazov (VKOYLAZOV)
archived on 30.4.2002

A short animation rendered with Direct GI at about 18 minutes per frame:

Follow-ups

Q: I have just tried using direct GI on one of my models and it seems to take considerably longer for not such a good result...
Why did you choose Direct computation over an irradiance map?
A: Because of the detail in lighting that you get. The irradiance map tends to blur the GI, and didn't look so good on the cathedral. I can render the same animation with the irradiance map so that you can compare the two.

Q: I take it that the direct GI renderer is comparable to the Brazil renderer. If so, why is there no more options to play with than just sub-div?
A: It is not exactly comparable to Brazil's GI, unless you check 'Lock to image rate' in Brazil. By default Brazil also undersamples the GI, although it uses a different interpolation method that preserves details better - but is difficult to use effectively with DOF, motion blur and reflections/refractions since it is strictly image-based interpolation. This is based on my observations of the alpha of Brazil though, things may have changed since then.
The problem of finding good interpolation methods for GI that preserve details well enough is long known in computer graphics and there is a lot of research done in the field, but I don't know of a 'perfect' method - all of them have some drawbacks...

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