Hi!

I'm trying to export a sand simulation from Houdini as .abc and import it to Cinema 4D so I can render the particles with Arnold.

The issue starts once I get it imported into Cinema 4d (points for some reason need to be imported “As Polygon Object” and not “As Particle Geometry” or else they don't appear). After converting the imported geometry to Cinema's “Particle Geometry” and adding an “Arnold TP Group”, the rendered particles appear quite large - and there is nothing I can do about it. “Arnold TP Group” settings regarding “Radius multiplier” do not change anything.

Does anyone have an idea what might be the reason? Probably something to do with the Alembic file's points being imported “As Polygon Object”?

P.S. I'm very new to Houdini so exporting Digital Assets is very tricky for me - this is why I'm avoiding it and why I'm trying to use Alembic export istead.

I just exported particles from Houdini using Alembic and opened it inside C4D using TP NOT geometry and if I turn the Radius Multiplier to 0.01 I see the particles smaller.

can you share a bit more information about your setup?

Make sure you're using “Open” to open the .abc file in C4D and not Merge. Merge seems to have a bug and doesn't show particles. I'll report it to Maxon.

Cheers

Hi Admir,

if you import the alembic as polygons the particles are imported as disconnected vertices without any of their attributes, which is fine if they are to be used for a cloner for example, but otherwise you need to import them as particles geometry. Note that they come in as Thinking Particles particles, not as “regular” cinema particles.

Now here's the kicker: in theory, you would now be able to access the attributes through TP Data Channels. However, due to a bug in how Alembic is implemented in C4D, currently Cinema does expect the attributes to be on the root level of the Alembic file when in fact they are all located beneath “arbGeomParams” (where they belong). And as far as I know, right now there is no way to get to them with standard c4d tools.

You can however overwrite the Size or Scale parameter in via TP in Xpresso and that is easily done. If you don't need the original attributes from Houdini and just want to scale the particles in Cinema, import them as Particle Geometry and run them through a simple Xpresso setup

Hi

So, I'm in the exact same situation but the problem I have with this setup is that the P Pass gets all the particles as a group, and not as individual particles… so I cant put individual spin, rotation and random size. Is there any solution to this?
Very frustrating to have a limitation like this for such a stupid bug.. specially because the workflow between Houdini>C4D>Redshift was working very well overall.