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View Full Version : The secret behind PRman's Motion Blur



cavalos
08-17-2003, 02:58 PM
Maybe this is will be too complex and technical post but, there are too many and different ways to simulate this effect accuratelly.
PRman always do a terrific job in terms of quality and speed but many other renderers like lightwave, mental ray or even Brazil have problems and slow the entire process too much.
So what is the secret behind it (at least in theory)?

Best
Christian

Lightwolf
08-17-2003, 03:43 PM
Hi cavalos,
PRMan uses a render technique called reyes.
For a (simple) explanation:
http://www.cis.ohio-state.edu/~rayt/cis781/cis781.html
http://dspace.dial.pipex.com/adrian.skilling/reyes/reyes.html
The thing is, it can jitter the micropolygons in space and time when it slices & dices them, so the actual geometry is jittered resulting in a nice sub-pixel motion blur and depth of field...
This also allows for "real" displacements btw.

It does have its drawbacks though, since it (initially) only slices the visible geometry, that's why the early implementations of reyes had no raytracing.
This has changed over the years though, the latest PRMan supports raytracing as well as GI and caustics...

Cheers,
Mike

harhar
08-19-2003, 07:14 PM
really slow raytracing and GI BTW.

Lightwolf
08-20-2003, 01:50 AM
harhar: True, but really fast sub-poly displacements (esp. compared to LW ;) ).