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View Full Version : Quick I need expert! Motion blurr question?



fronzel
01-24-2004, 07:09 PM
Does motion blur have any significant effect on render times?

I have not noticed this before.

But it could be be costly. Deadline approaching. And I've need to accruatly calculate my render time.

Thanks

fronzel
01-24-2004, 07:15 PM
I'm flipping threw the manual right now.

Like most things I go to the great book for it gives a very general explanation.

It does say that using dithered Mblurr Is better quality at only a third of the next higher AA level.

WizCraker
01-24-2004, 08:30 PM
Originally posted by fronzel
Does motion blur have any significant effect on render times?

I have not noticed this before.

But it could be be costly. Deadline approaching. And I've need to accruatly calculate my render time.

Thanks

You could always add Motion Blur in Post

js33
01-24-2004, 09:06 PM
Yes Post. Of course it depends on what you are doing but if you are in a hurry I would isolate the elements that need motion blur and render those out seperately with an alpha channel and just blur it in post. AE has goodlooking and fast motion blur.

Of course AEs motion blur is 2D instead of 3D.

Cheers,
JS

stib
01-25-2004, 06:00 AM
Motion blurring in post? For a still image, yes, but wouldn't it be very tricky to achieve realism on an animation?

I thought that motion blur didn't really add much to your render time if you were already doing multiple passes for AA, unless you choose dithered motion blur.

*Update - I did a little test. I rendered a scene of a cube moving across in front of the camera at extreme AA. It took 17 seconds to do a frame with no Motion Blur, and no fields. It took the same amount of time with and no fields and normal motion blur with a "shutter angle" of 360 degrees, and it took 25 seconds with no fields + Dithered motion blur.

No motion blur but with fields took 25 seconds, and once again the same amount of time (25 seconds) with normal notion blur - you can't do dithered MB with fields on.

I noticed that while rendering dithered MB the status window showed "now rendering frame 10a" then "10b" as if it were doing fields. LW seems to do motion blur by stepping through the action as it does each AA pass. I'm not sure what its algorithm is for dithered MB. Hope this helps.

WizCraker
01-25-2004, 02:16 PM
Yes motion blur in post across multiple frames works.


*Update - I did a little test. I rendered a scene of a cube moving across in front of the camera at extreme AA. It took 17 seconds to do a frame with no Motion Blur, and no fields. It took the same amount of time with and no fields and normal motion blur with a "shutter angle" of 360 degrees, and it took 25 seconds with no fields + Dithered motion blur.


Try adding a little more geometry with motion blur and you will see that render time go through the roof.

toby
01-25-2004, 02:27 PM
Vector blur is another fast-rendering option.

fronzel
01-25-2004, 03:50 PM
I made it! whew. I haven't hardly slept in a week I've been pulling 20hr shifts trying to get this done on time. The client got the stuff and they love it!

I worked extra hard on this because it's a going to be a national spot. So look for my singing dancing phone. When it airs I'll give more details.

Here's a pic.

js33
01-25-2004, 05:54 PM
Cool. Glad we could help. How did you get to work on a National Spot? I need to hook up with more Ad agencies.

Cheers,
JS