View Full Version : Photoreal Motion Blur SUPER time lag.

09-22-2008, 06:38 PM
Hi All,

I'm not sure I entirely understand what's really going on here, but let me set it up...

LW 9.5.

Locked down REAL LENS camera.
Two large snakes slither around a corner and mid frame they split ways, one goes off screen right through a doorway and the other stays going straight and under the camera.

The scene is 101 frames long. 1920x1080 resolution. 9 anti alias passes.

Photoreal motion blur. 1 pass.

All other settings default.

Frames 1 through 50ish render in under an hour each.
Frames 70 through 101 render in under an hour each.

Frames 50 through 70 (the frames at which point my right hand side snake makes his way out the right hand side door midframe) take anywhere from 2 hours to over 15 hours (don't know the actual final time, I had to abort).

Went back and re-rendered the exact same scene.. only this time with CLASSIC CAMERA and DITHERED MOTION BLUR, and the entire scene rendered in under an hour.

At first I though it might have been my radiosity.. but long ago I had turned that off and rendered with straight DISTANT lights... but in the end, it was the PHOTOREAL motion blur (and/or) the REAL LENS camera.

I read somewhere else that PHOTOREAL blur has problems with objects that are deformed via bones? If this is true, that is the case, because the snake has to turn and lifts his head at the point he exits... the same frames that take exponentially longer to render.

Any thoughts/fixes/work arounds out there?

At this point, since this appeared overnight during a crucial render, I am scared out of my wits of PHOTOREAL blur!!!!

Thanks for hearing me *****. It helps to know there are others out there who understand.. (and BTW, I still love LW...) :)

Steven Blasini
Visual Effects Supervisor
BFX Imageworks

09-22-2008, 06:54 PM
Yes anything that is deforming will require more motion blur passes. Try less AA passes and more motion blur passes.

Maybe AA 2 MB 4 AS .1

But thats just guessing.

09-22-2008, 07:16 PM
Thanks, Castius for your thoughts.

09-26-2008, 01:55 PM
My direct comment on such long render times is that I personally would skip the 3D program motion blur and do it in post instead! Life is too short for actions that donīt happen!

However it would be nice to see some shots from your rendered scenes!

09-28-2008, 12:18 PM
Just use Adaptive Sample 0.01-0.03 for nice MB or 0.05-0.06 for rough ... Photo real MB NEED Adaptive sample, so u can drop your AA to 1-4 and MB to 1 and use Adaptive Sample. Bones deformation don't have any restrictions with Photo real MB , the only case there u need more then 1 MB passes is a motion blurred reflections of bone (or any deformed) objects.
For more information about AA and MB check the Exception's AA guide (http://www.except.nl/lightwave/aa/index.htm)