points as volumes

[nwebber5Z7PJ]

Hi, is there a way to render points as volumes in Solaris? Something I need to set? (other than converting to vdb which can be quite heavy)

Cheers

[AkiraEndo2521]

I'm also very interested to find out how to render points as volume in Solaris.

Any help is appreciated.

Thanks

[peterDTE7K]

I guess there is no other way than converting points to VDB. There are multiple ways to do this in Houdini. Points from volume node to generate dense volume of points from geometry. Attribute wrangle (points) node to add density to points (f@density=1;). Volumerasterizeattributes node to convert points to vdb - set attributes to density and set proper voxel size and particle scale. Assign material with arnold standard volume.

Arnold will not work with standard houdini volumes, you always want to convert those to VDB with convert node before rendering.

[nwebber5Z7PJ]

thanks for your reply, but this is not what I'm asking. I am am looking for the solaris equivalent of this:

[AkiraEndo2521]

Thank you for clarification. That's what I feared.

Based on a smoke sim I already animated points with the help of popadvectbyvolume.

And finetuned pop motion by age and traveled distance. 

I did hope, I could avoid to convert it all again to a volume.

[Stephen.Blair]

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@nwebber5Z7PJ wrote:

thanks for your reply, but this is not what I'm asking. I am am looking for the solaris equivalent of this:

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Render Geometry Settings?

[AkiraEndo2521]

It seems, this option does not work.

It does not change anything. It doesn't matter which values I enter at step size.

Points will always render as points.

[nwebber5Z7PJ]

AkiraEndo is correct. Its doesnt seem to work.

[nwebber5Z7PJ]

Also, tried this in a wrangle, but no effect:

usd_setprimvar(0, "/sopimport2/FX/Particles0", "primvars:arnold:ar_step_size",.4);

It seems to work on meshes, just not points.

[Stephen.Blair]

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@nwebber5Z7PJ wrote:

Also, tried this in a wrangle, but no effect:

usd_setprimvar(0, "/sopimport2/FX/Particles0", "primvars:arnold:ar_step_size",.4);

It seems to work on meshes, just not points.

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There is no Arnold parameter named "ar_step_size"

The "ar_" is something used by the HtoA plugin only.

It would be primvars:arnold:step_size

[nwebber5Z7PJ]

This is what I have:

usd_setprimvar(0, "/sopimport1/points_0", "primvars:arnold:mode", "sphere");
usd_setprimvar(0, "/sopimport1/points_0", "primvars:arnold:step_size",.4);

I have a volume shader assigned. Yet they do not render.

[Stephen.Blair]

Got an example scene you can share?

[nwebber5Z7PJ]

I'll make a simple scene for you to test.

[nwebber5Z7PJ]

heres  a simple test scene to try,. Hopefully i've just done something stupid.

[Stephen.Blair]

Thanks for the scene file.

In this case, there's a bug. HtoA isn't processing the shader connected to the volume port, so the points are rendered with a simple fallback surface shader.

Workaround: connect the standard_volume to the surface port of OUT_Material. It will show an error, but now the points will render with a volume shader.

[AkiraEndo2521]

Thank you! That did it.

[nwebber5Z7PJ]

Yep it works! Thanks Stephen!