Volume Motion blur

[ghiom3d]

HEllo

I have trouble to render my volumes with motion Blur with RTX
I setup up my camera , my obj nodes and the vray ROP to do motion blur with velocity.
My cached volume have the velocity attribute but even i push the multiplier in shader to 100 i don't see anything. My camera have enought time to do motion blur, my meshes are motion blured and move slower than my volume.

I've try to split the vel attribute to 3 vel.* , but same result.

i've try in CPU mode, same thing.

Can you help me?

Houdini indie 19.0.498 // vray_adv_52020_houdini19.0.498_4507299_20994_insta ll_windows // Win11

[chakarov]

Hello ghiom3d , seems to work on our end. Can you double check if your velocity volume is scalar or vector one. The "vel.*" expression is for separated X,Y,Z scalar volumes , if your velocity volume is vector one the expression should be "vel". If this doesn't help, can you share your Video Card model and Video Driver version ? Simple scene will help as well.

[ghiom3d]

hello Georgy, I have try with a vector velocity, that's how it's saved in my Bgeo.sc volume cache.. and because i don't see any motion blur, even everything seems setuped ok, i've add a node vdbvectorsplit to split vel in vel.x vel.y and vel.z. i will try to do a simple scene for you

my Nvidia driver is Studio 511.65 on a 3080-ti and 2080

[ghiom3d]

i've find a way to make it work .
I need to blast temperature, in info temps is [0, 0, 0 ] so i don't use it.
then i split velocity and density because for optimising my scene, velocity is 1/2 scale of density. that's the way i work since years for now.

so i use a vdb resemple node to resample my velocity as the same resolution than density.
then i merge them together
and i need to convert this reconstructed vdb fog as Volume and not anymore Vdb fog.

Now motion blur work and i have velocity it in AOVs.



Is my fault was to undersample velocity ? or because we need to convert to Volume instead of VDB FOG ?

[ghiom3d]

and i see i can add again a vdb convert to convert this VOLUME to VDB Fog and it's work .. very strange !

[chakarov]

Definitely strange, can you share a scene, even simple one, where the problem occur ?