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Shagrinar
09-19-2009, 09:44 PM
Hello CGSociety,

I always wanted to make a long exposure picture in 3ds Max but I don't know how to do that... I tried to use mental ray with mr Photographic Exposure Control with normal lights and photometric and also with volumetric lighting but it's still not working...

Can someone help me? Would be great :)

Thanks!

CHRiTTeR
09-20-2009, 03:19 AM
If you mean doing something like this:

http://upload.wikimedia.org/wikipedia/commons/c/c5/Long_exposure_shot_of_fire_poi_ball_dance.jpg


You're gonna need A LOT of samples ;)

Shagrinar
09-20-2009, 07:45 AM
Yes, that's exactly what I mean...

A lot of samples of what? Motion Blur?

CHRiTTeR
09-20-2009, 12:13 PM
Yes, use motion blur with a long shutter time and enough motion blur samples (longer shutter time -> more motion blur samples needed).

Shagrinar
09-20-2009, 12:23 PM
ok, thanks - ill try it :)

gerardo
09-23-2009, 09:52 PM
You could try by rendering with a common number of samples, shutter angle and exposure time. Later in a compositing package, you could exaggerate the mblur effect.

I showed this in a Lightwave thread but the process is applicable in any package. The effect used in post was Echo filter from AE:

http://imagic.ddgenvivo.tv/forums/spark.gif

This filter can slow down sensation of speed:

http://imagic.ddgenvivo.tv/forums/eco_blur.gif

so you may want to stretch the duration of the final comp.



Gerardo

pptc
10-05-2009, 12:12 PM
I interesting in this effect too.

gerardo show very nice result with sparkle.
If you need real 3d motion trail, think simply motion blur with huge sample is not solution.

I get some test - result not be good, even render time to infinity.
I can solve it with good result only in Houdini, but a little tricky (caching geometry)

http://www.pp.tc/mega/HOUDINI/transform_motionBlur_multiSegment_particlesROP.jpg (http://www.pp.tc/mega/HOUDINI/transform_motionBlur_multiSegment_particlesROP.hip)
(on image - random motion of particles with trail around 50 frames)

CHRiTTeR
10-05-2009, 04:33 PM
Yeah, its kinda heavy to compute.

If you were uding max you dould use something like motion trails (not free) or ky_trails (free).
Not really motionblur, but for what you're asking it works just fine.

Maybe something simular excists for maya?

But if you want absolutely correct results, motion blur is the way to go im affraid.

pptc
10-05-2009, 06:02 PM
Yeah, its kinda heavy to compute.

If you were uding max you dould use something like motion trails (not free) or ky_trails (free).
Not really motionblur, but for what you're asking it works just fine.

Maybe something simular excists for maya?

But if you want absolutely correct results, motion blur is the way to go im affraid.

I not remember in detail, how I do it in Houdini, but calculating with tricky caching is realy no very expensive rendering in Mantra (internal renderer).

But in Maya or 3Dsmax etc., think is not possible internally without writing some kind of plugin.
Even Pixar Renderman has limit to motion sample 6 or 8 => is be not very accurate on very long motion.

CHRiTTeR
10-05-2009, 06:11 PM
I not remember in detail, how I do it in Houdini, but calculating with tricky caching is realy no very expensive rendering in Mantra (internal renderer).

But in Maya or 3Dsmax etc., think is not possible internally without writing some kind of plugin.
Even Pixar Renderman has limit to motion sample 6 or 8 => is be not very accurate on very long motion.

you could use a particle system to leave trails behind and let them fade away over time (thats how Ky_trail does it)

Maybe max's multipass camera effect can give you satisfying results (i dont have much experience with it, so its just an idea/suggestion).

I know vray's motion blur is relatively good at it, i've used it for that in the past.
But i assume you dont own vray.

Anyway its hard to say how you could do it best without any info about scene setup etc...
Theres a few ways you could do it. It all depends on a lot of things.
And dont expect it to be lightning fast either. Some times you just have to accept the fact thing are pretty heavy to calculate.

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