Motion Blur Shutter Offset?

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Motion Blur Shutter Offset?

Postby s---70 » Sun Jun 19, 2016 9:16 am

s---70 Sun Jun 19, 2016 9:16 am
Could you implement a shutter offset for motionblur? Or is there such an option somewhere already?
Yesterday I tried to render a meshed fluid with motionblur, which made the initially smooth surface really noisy because the velocity vectors on the fluid mesh were a bit messy and the mesh got transformed by the velocity vectors to the middle of the frame. I think if I could set the shutter offset to the beginning of the frame this could be avoided.
Thx!
s---70
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Re: Motion Blur Shutter Offset?

Postby juanjgon » Mon Jun 20, 2016 10:44 am

juanjgon Mon Jun 20, 2016 10:44 am
I am not sure what could be the problem in your scene. The motion vector is the motion computed by the simulation for the current frame. The deformations motion blur in the mesh is computed from the base geometry at the beginning of the frame, deformed using the motion vector multiplied by the shutter time.

If you want to share the scene, I could test the motion blur problems here.

-Juanjo
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Re: Motion Blur Shutter Offset?

Postby s---70 » Wed Jun 22, 2016 7:23 am

s---70 Wed Jun 22, 2016 7:23 am
Here it is with deformation MB enabled:
untitled1.jpg


and here without:
untitled2.jpg


obviously fluids motion vectors are not very exact because the topology changes on every frame and the motion vectors are interpolated from a vector field. That leads to visible breakups on smooth surfaces. I could try to smooth out the motionvectors somehow but it would be nice to just render the mesh on frametime 0.0 to get rid of them. Or is there another option to smooth out the normals after motion blur deformation? Because setting the "smooth angle" in the octane properties doesn't affect this.

Do you still need the scene?

Thx
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Re: Motion Blur Shutter Offset?

Postby juanjgon » Wed Jun 22, 2016 7:58 am

juanjgon Wed Jun 22, 2016 7:58 am
Yes, please, attache the scene to test it here.

Anyway, the base mesh is the topology at the beginning of the frame, and the deformation MB is computed translating the vertices from this base topology using the motion vectors. So perhaps the problem is that the motion vectors are not properly computed, or there is other problem with the scene.

-Juanjo
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Octane plugin development and support: LightWave and Houdini
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