Particle instancing no motion blur..

[Komposer]

Hi,
I´m working here on an instancer job.
Maya 2012, V-Ray for Maya version 2.20.01 from Feb 1....

When I cache the particles, what I need for the farm, the motion blur don´t work - its off!
When I render it without cached particles, inside one machine from first frame on - it works - but that need much to much time!

Where is the mistake?
What can I do - please help.

Thanks,
Jörg

[vlado]

Are the cached particles referenced? Also, are they particles or nParticles?

Finally, what are your motion blur settings (inverval center and duration) and cache sub-samples?

Best regards,
Vlado

[Komposer]

hi Vlado,

I work with nParticles.
No reference.
9 objekts in loop mode for a wings cycle.
I´m using the MB from inside the physical cam, which is in still mode, so I´ve only the enable MB option. (or?)
The subdivs makes no diff if high or not, but I set it to 16.

What is "cache sub-samples"?

Thanks

[vlado]

Ok then; can you post a simple version of the scene or email it to me at vlado@chaosgroup.com? I remember some trick was needed to get this to work, but I can't remember what it was right away.

Best regards,
Vlado

[alainfx]

Not sure if it's the same problem, but just in case (this one was resolved) :
http://www.chaosgroup.com/forums/vbu...no-Motion-Blur

And I remember that you need to be careful with this setting :
Render Settings-->VRay-->Camera-->Motion blur-->Duration (frame)
If you have a particle cache, the Duration setting must be an integer number, it would not work with a floating value.

Alain

[vlado]

If you have a particle cache, the Duration setting must be an integer number, it would not work with a floating value.

It depends; there are ways to make it work by adjusting the cache settings. It would be best to look at the particular scene though.

Best regards,
Vlado

[Komposer]

thanks guys for help,

Vlado, I sent you the scene!

Nothing helps - it will not work.

I tried every case - with physical still cam and movie cam...
With out motion blur on inside the phys cam and switched on inside the render settings "Cam - motionblur"...

In the moment I cache them, the motion blur don´t works!

But when u render it without cached, as example frame 70, it woks perfect with the phys cam and the inside MB!

BTW...
please try to render the same uncached frame twice or more - every rendering brings another result of birds positions!!
That is for me spookey too.

And when I play around with the shutter speed (also uncached!) I get strange results too.

Perhaps I dont understand here some basicly things!?
But in reality, the mb must work with phys - still cam - what it do, but strange things happens.
And in reality when I set a shorter shutterspeed, mb must become stranger - or not?

Thanks so much,
Jörg

[vlado]

And in reality when I set a shorter shutterspeed, mb must become stranger - or not?

Yes... Smaller shutter speed means the shutter is open for a longer period of time (remember that the shutter speed units are s^-1). In reverse, larger shutter speed values mean the shutter is open for a shorter period of time. In any case, for an animation you'd be better off using the Movie camera type.

Best regards,
Vlado

[t.petrov]

Komposer:
I've played a bit with your scene and the problem is that your motion blur setting cause V-Ray to sample your particles at times where there is no cache for them.

If you look at the log, you'll see something like this:
[2012/May/8|14:23:15] V-Ray: Updating frame at time 70.00
[2012/May/8|14:23:15] V-Ray: Updating frame at time 70.42
So V-Ray is sampling the particles at frame 70 and frame 70.42.

Even if you create the cache with "evaluate every"=0.5 it won't work.
This happens, because the nparticles are not interpolated, when there is cache, but the previous value is used.
And the result is that the scene looks like the scene at frame 70 instead of the real scene.

What I've done in order to fix your scene is:
1. I've switched the camera type to "movie camera" (when doing animations this is the preferred type)
2. Created the cache with "evaluate every" = 0.5

And now when V-Ray samples the particles there is cached data for every sampled frame.

Hope it helps,
Teodor