Vray -> Post Mblur (beginer questions)

[Jynks]

Hi there

Still learnign Vray basics here.

I was woundering how Vray handels vector renders.. I assume that the render element velocity is the element to render.

Still once i have this render done.. what do you do with it.

I made a simple test of cone moving along a path and rendered it out as exr with a velocity channel. The velocity chan looks exactly like the normal render (in a way)

The Red and Green chans have a copy of the object and the Blue chan is empty.

Once i have this render.. how do I use it?

[instinct]

Hover your mouse over them and take a look at the actual float values. They appear as white (1.0) as this is the max to be displayed on a monitor but actually have a LOT higher values.

As you are using nuke, add a multiply node and multiply the g chan with -1, then add a vectorblur and select the velocity as uv input, dadaaa :P

Then read up in the docs about the different settings and when yo use wich mode as that is somewhat crucial to get a usable result.

Regards,
Thorsten

[vance3d]

Generally I think the workflow is to first do a render that has a lot of motion in it and check the value returned in the "max velocity in last frame" attribute of the velocity render element.

Put in a value a little bit higher than this into the max velocity setting.

Make sure z direction is ignored and then render out to an exr file through the vray frame buffer rollout.

Most post mblur effects rely on using the the r and g channels to interperet the x and y motion. Real Smart motion blur does this with its motion vectors effect.

So in after effects you would have to have the exr tools from pro-exr loaded (which are free) so you can reveal the vector render in AE and use this as a source for the vector mblur effect.

V Miller

[instinct]

As he seems to be using nuke that's not really needed as long as he renders to full float EXRs. The actual scaling of motion values only brings in marginal rounding errors for higher values.

Regards,
Thorsten