Nuke Motion Blur From Imported 2D Motion Vectors

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Old 03 March 2011   #1
Nuke Motion Blur From Imported 2D Motion Vectors

Hi !
I've recently started with Nuke, my compositing tool of choice at the moment being Fusion.(I miss Shake so much.....)
My problem is that i want motion blur from exported motion vectors.The motion vectors are exported into exr format from Maya (mv2DToxik pass).I simply render the scene with no lights and a black surface shader.In fusion, i simply copy the x and y velocity to the corresponding channels in the exr options, and plug it to motionVectors blur.
In NukeX 6, the exr options are missing.I checked raw data and messed up with the layers and channels (it's such a mess) and the 2DMotionBlur but no solutions.
Some advices would be appreciated , since making motion blur in 3D is stupid ( except rotating objects -helicopter blades, etc and some special cases).
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Old 03 March 2011   #2
Have you tried F_Kronos? you need to change Speed to 1. it works good but The Foundry recommends F_Motionblur. You can use VectorBlur either to generates vectors and it puts the output vectors in Motion Channel. Later you need to activate it in other nodes' channel if you wanna use it.
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Old 03 March 2011   #3
Thank you !
I didn't know about F_MotionBlur and K_Kronos. Kronos is weird. It seems to me that F_MotionBlur is working fine without motion vectors...I guess is that is analyzing the pixels movement between frames and estimate the amount of motion.
My problem is that i want smooth motion blur from vectors, but no matter how high my samples are, the motion blur smoothness is the same.
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Old 03 March 2011   #4
its quiet simple in nuke, nearly as simple as in fusion but its another app so another workflow

see screenshot as example
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File Type: jpg screenshot.jpg (78.2 KB, 244 views)
 
Old 03 March 2011   #5
Of course! This is what i was looking for ! Thank you for the trouble with screenshots ! Much appreciated !

PS: If i have an exr, my motion vectors are on other channels, so those must be the copied.Initially i tried to copy the motion channel, so that was wrong.I've put a screenshot just in case somebody stumbles into this again...
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File Type: jpg screenShotA.jpg (95.6 KB, 128 views)
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Last edited by alienpioneer : 03 March 2011 at 07:18 PM.
 
Old 03 March 2011   #6
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Old 03 March 2011   #7
If your vector blur is going in the wrong direction then you may need to add or subtract .5 in u or v. Different motion vector shaders have their origin in the center of the frame or a different corner.
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Old 03 March 2011   #8
Thank you!
I am working with the motion vectors directly from maya, in exr format (mv2DTokix pass).No shaders, no more headaches.I've been testing the mv in Nuke with the example from the last post, and i didn't notice any trouble.It works like a charm.I've also used maya mv in Fusion for some time, and still no errors.
Though , I will keep in mind your advice .Cheers !
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Old 03 March 2011   #9
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