Can't Adjust Motion Blur Intensity On Rop:ed Animation

[Daiboushi]

Greetings!

I have done some animations on simple polygon planes which I rendered out to a bgeo-sequence. But when I later used this bgeo-sequence in a render with motion blur, I found to my surprise that I couldn't adjust the motion blur intensity on the camera. It would either blur everything with a fixed value or give no motion blur at all when I drag the Shutter Speed slider around. And I can't find any other posts on this forum about this issue either. Is there any solution to this or any post out there that I missed?

[symek]

as I understand you're rendering using velocity. If so you can adjust its value according to your needs. Treat it as any other attribute on geometry and multiply by 0.5 for example. This will make your motion blur smaller. Perhaps the easiest way to do this is to create trivial VOP SOP with "v" multiplier.

hope this help!

cheers,

sy.

[Daiboushi]

Thanks for the quick reply SYmek!

Hmm, as I understand it (from my limited knowledge of Houdini) I haven't got a velocity-attribute on my meshes. I thought you only had that when you use particles? I'm currently using deformation blur since it happens within a geometry. Does deformation blur take the velocity-attribute into account if I add it to all of my points (and of course calculating the right velocity for each point)?

[symek]

I don't know the technical differences between velocity and deformation blur (how they are computed) but in general I hardy see any differences between images. Velocity blur CAN also be used with geometry (not only particles) and has this beautiful advantage to be controllable via velocity attribute.

You can create velocity attribute with Trail SOP (change "result Type" option for proper one). You can adjust its scale with a "Scale" parameter.

The question remains why your deformed geometry behaves like that? Maybe deformation is too big. No idea here, sorry.

cheers,

sy.

EDIT:

After studying some posts here I would assume that deformation blur is computed pretty similar to velocity based blur. The difference is that in deformation blur mode mantra computes point position difference between frames assuming equal point count. In velocity blur case mantra doesn't compute the rate automatically but expects velocity attribute existence. Trail SOP and few other methods can do it for you. Because its not computed internally by mantra it's easy to manipulate it (even paint on a surface with a brush!). But the results of both methods should be the same in equal conditions.

Edited September 13, 2007 by SYmek

[SpencerL]

You can create velocity attribute with Trace SOP (change "result Type" option for proper one). You can adjust its scale with a "Scale" parameter.

I think you mean the Trail SOP to compute velocity.

[symek]

yep, you're right! thanks!

[thekenny]

are you reading the geometry from disk via a fileSOP?

-k

[Daiboushi]

Sorry got too much work yesterday to answer. Thanks for the interesting info about velocity and deformation blur. I did a test with it just now and I must say it works awesome! This resolves my problem.

thekenny: Yes I use a FileSOP to read in my geometry from disk.