View Full Version : mental ray motion vectors to blur in Nuke

07 July 2010, 07:47 PM
I have been searching online for tips on how to do motion blur in post from elements rendered with Mental Ray. I have yet to find a good explanation on what to do in Nuke, what kind of motion vector will work from Mental Ray. Has anyone gotten a good result that they used in production?

I am having difficulty figuring out what the node graph setup would be in Nuke. Some say that what is needed is a vector blur node, others say you ALSO need a motion blur 2D node... I just don't know any more... I am also reading about needing to plug in expressions to offset the values for u and v channels, but I am not sure how to do that, either....

Any help would be great!

07 July 2010, 10:00 AM

this image was composited in Nuke...

first .. in maya .. i made motion vector pass with
((puppet shader - motion to RGB shader)) ... it will give
you a perfect effect...

then inside nuke make this tree

plug the MV pass as (input 1) in shuffleCopy thin "forward channel" as U, V channels
and plug the default color stream in (input 2) as (RGBA)

and in the vector blur node ... just select the channel "forward" because in the
shuffle we plugged the motion vector pass as forward ((U, V))..
and begin playing in values to choose the right values to the Mblur

:thumbsup: i hope this could help you

02 February 2011, 05:02 AM
Wow I just saw this...
thanks for posting it. I don't usually like to use the puppet shaders, but I'll give this a look!

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02 February 2011, 05:02 AM
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