motion vector for volume

[Benyee]

I have a pyro sim,and I want to render a motion vector pass of the volume elements used by RSMB in Nuke,how to set up,thanks.

[fayal]

same problem hope anyone can help.

[almatea]

you can use deep compositing, deep camera map image

although if your smoke has hi density you can just use vel primitive for setting color attribute in your shader

[fayal]

thank you vladislav

very useful tip.

[Neil78]

Hi - i found this method

in your shader (pyro or whatever) get 2 getblur nodes. Hook up 2 constants in their inputs - one set to zero the other set to 1.

Now subtract getblur 0 from getblur 1. Finally export as a direction vector attribute called whatever ( motionVector)

Render your AoV of 'motionVector'

In Nuke - shuffle your rgb motionVector data, ( or whatever you have it as) into Nuke's motion channel. Now normalise the data.

I use 'MV2Nuke' - get it on Nukepedia.

Throw this into Nuke's vector blur.

Thsi works for me very well.

[fayal]

thank you ,

it not work for me!!!

any example for your method.

[Neil78]

thank you ,

it not work for me!!!

any example for your method.

Hi Fayal - basic hip attached. It just has a a pyro shader with the motion vectors export set up inside of it - as well as a mantra rop with the AoV set up i created.

Regardign the AOV setup - In Nuke i tend to re-render the houdini EXR's as seperate exr passes in just RGB -

Remeber to normalise the motion vectors in Nuke before using the vector blur.

motionVectors_Setup.hip

[fayal]

thank you again Neil Scholes.

[mohit]

Regardign the AOV setup - In Nuke i tend to re-render the houdini EXR's as seperate exr passes in just RGB -

Remeber to normalise the motion vectors in Nuke before using the vector blur.

Being new to Houdini Could you help me by providing explaination why do we need separate masked exr in 16 bit ?

And How and why we need to convert it in RGB  and latter normalise it?

Do I need scattering pass if I am using volume light?

Also how does it help turning on "Motion Blur" and "Depth of field" option in sampling for motion vector pass.(It's on in your file)

[waterzhou]

hi...arnold can render the pyro motionVector? i do not know how can i  get it,who can help me,please!!!!

Edited August 8, 2016 by waterzhou