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VDB combine sphere + polyextrude custom surface attribute.


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Hello everyone,

I have just started using Houdini but I'm stuck following a VDB tutorial from Entagma with my own object.

Basically, I have a kind of barchart created using a custom attribute H on the primitives of a grid via a polyextrude node. I can't transform it properly into a VDB regardless of the voxel size if I use fog or distance. Yet it works if I add a custom surface attribute on the VDB. Now that I have my barchart volume, I cannot VDB combine it with other volumes. I tried specifying the group and play with all parameters but I have this error:




I have linked the project to make it clearer.

Thank you very much for your help.



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Hey Kikohs,

I'm not able to upload a file at the moment, but hopefully I can help anyways!

First thing: your polyextrude is currently only extruding, but not creating a closed object. Make sure "Output Back" on the Extrusion tab is checked to have it create a closed object. VDBfrompolygons requires a closed object to correctly generate a VDB.

Next, turn the Distance VDB back on in the vdbfrompolygons.

Finally, in your vdbcombine clear the group fields as it will use the surface volume by default (which I believe is what you desire).

Let me know if you have any other questions!

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