aiMotionVector not outputing data in maya 2019 /Arnold 5,.3.1.1 for Ornatrix hair

Posted by:matthewb
Data created:1 August 2019

Hi, we are not getting any motion vector information on the Ornatrix hair system in our renders.  


Please advise. 

Hello Matt,

Can you please give me instructions on how to test this? I'm not really experienced with this topic. 

Jeordanis Figuereo (Product Designer. EPHERE Inc.)

for testing purposes on your end, 

Create an AOV. call it anything .. MotionVectorTest.

Animate some hair. 

in the new aiAOV you have created, plug in an aiVectorMap to the Costom AOV shader input.   and in the input of that aiVectorMap node. plug in an aiMotionVector node. 
aiVectorMap_mblur.outValue to aiAOV_MV_Utility.defaultValue
aiMotionVector_mblur.outColor to aiVectorMap_mblur.input


turn on motion blur in your render globals and test render. 

in the AOV of the new render you shuold see motion vector colors on the hair. 

The reason for this is because 3D motion blur though effective, leaves alot of artifacts in spec ect and to fix that the render times go way up.  So this motion vector AOV provides comp the control to effectivly produce the same resule of ins scene motion blur without artifacts, noise and high render times. 


Thank you, I will give it a try. 

Jeordanis Figuereo (Product Designer. EPHERE Inc.)