IPR volumes size

[psanitra]

When shading volumes in IPR and switching from volume to volume geometry, volumes changes size . W10, CPU ,build houdini17.5.293_29c900e_4988"

Edit : it changes size when doing other stuff too, like turning on/off light cache speed up

[chakarov]

Hello psanitra and thanks for the feedback. I've reproduced the issue and reported it. I'll message you back when it's fixed.

[psanitra]

chakarov thank you. While we`re at the volumes topic, i was trying to displace the volume at rendertime, feature i use for volumes/vdbs in 3D max, but i can`t get it to work in VHF.
I did not find anything in the docs on this topic(except the setting should be in rendering tab, which they are not) , but i assume we should connect displace color/texture to the disl2(color) input. But that does not do anything.I tried Vray noise, even with different uvwgen,2D ,3D, but no go. Is this feature implemented or not?

thank you

[Gosho.Genchev]

Hey there,

I was hoping we can eventually add a specific projection node which is used in Maya to support projection mapping. Also, there is no way to use Advection displacement at the moment since that would require a texture which can read a grid channel (e.g. the Phoenix FD Grid Texture).

For those two reasons, displacement is hidden from the UI right now. You can unhide it manually from the Gear icon on the volume shader -> Edit Parameter Interface. You need the Displacement and the Surface folders.
1. Disable "Invisible" for the Displacement folder
2. Find the "Surface" folder and remove the "Tab Hide When" condition
3. Set the Surface Channel to Smoke
4. Plug e.g. a Checker texture in displ2
5. Attach a UV Object mapping to the texture uvwgen input

If you'd like to tweak the mapping, you can use a UVW to Color -> RGB Multiply -> UV Explicit between the UV Object and the Checker nodes.
I've attached an example scene here: https://drive.google.com/file/d/1XdO...ew?usp=sharing


Hope that helps.

[psanitra]

Gosho.Genchev Thank you for the file, works.

It will indeed be nice to have those options you mentioned, Advection, and projection mapping support, for some Lee Griggs style displacements(his displaced volumes show up quite a lot on my clients reference, lol).

I was also trying to use vray nodes like falloff, or even sampler to modify volumes look but it was not working, also not when using volumetric geometry. For example setting volume color by the gradient from red to blue color based on camera viewing angle,perpendicular/parallel, Fresnel, facing ratio etc. I understand that volume does not have surface, but in case of VDB it kind of does right..., 0 level...
Also for example on sampler node take the ray depth output base on that modify density of the volume etc. If some if this technical stuff could be possible that would make me very happy.

bdancer And best for last,.Can we get forward/backward scattering for volume shader?(i mean in vray general, all dcc) isotropic is so basic..., definitely not great for rendering clouds for example. Pxrvolume is pretty good example of what i`m looking for in terms of anisotropy and scattering.