Debri Source and Alembic

[TheDude123]

Hi,

I've got an alembic file that I need to create some debris from. However, when I unpack the alembic, throw it into a material fracture and wire up a debris source node, it doesn't quite work how I want it to. Problem is points are being generated on some of the edges of the outside face. I just want the points to be generated on the fracture edges.

Any idea as to why this is happening? I'm assuming it's something to do with the alembic file. I have another set-up that uses a simple box (no alembic file) and the debris source node does fine with that.

Any input would be great! Thanks!

See attached file for reference and image below.

Debris_Source_Cinema 4D_to_Houdini.hip

Voronoi_Fracture_Gradual_Break.abc

Edited April 5, 2021 by TheDude123

[underscoreus]

Heyo, if you want to share your hipfile remember to either include any external files like alembics or lock the import node (in this case the alembic node) so it saves the geometry into the hipfile you share. If not we just end up with an import error when we download and look at the hipfile.

As for your issue, there are two things I'd try.
1. Instead of "Edge debris" try using "Surface debris" instead. I've sometimes had it that the edge debris pushes points a little outside where they should be and I also just personally prefer surface debris since it uses the whole inside surface instead of just the edges.

2. You could try to use the group field in the "debris source" node to explicitly tell it what faces/edges to scatter on. By default it is looking for a group called "inside" I believe. Based on just running a normal box through your setup it does not get any faces in the "inside" group, only stuff in the outside group since the "fracture level" was set to 0. Maybe this is your issue? That there is no prims in the "inside" group?

[TheDude123]

See my post below.

Edited April 5, 2021 by TheDude123

[TheDude123]

5 hours ago, underscoreus said:

Heyo, if you want to share your hipfile remember to either include any external files like alembics or lock the import node (in this case the alembic node) so it saves the geometry into the hipfile you share. If not we just end up with an import error when we download and look at the hipfile.

As for your issue, there are two things I'd try.
1. Instead of "Edge debris" try using "Surface debris" instead. I've sometimes had it that the edge debris pushes points a little outside where they should be and I also just personally prefer surface debris since it uses the whole inside surface instead of just the edges.

2. You could try to use the group field in the "debris source" node to explicitly tell it what faces/edges to scatter on. By default it is looking for a group called "inside" I believe. Based on just running a normal box through your setup it does not get any faces in the "inside" group, only stuff in the outside group since the "fracture level" was set to 0. Maybe this is your issue? That there is no prims in the "inside" group?

AH! So sorry about the alembic file missing...long week :). I've included it in the original post.

I don't have a "inside" group in the alembic file...that may be the issue. That is something I noticed between the alembic file and the Houdini created version. I do have an "Inside_Faces_1" group (which does seem to help with the issue).

Thanks so much for the suggestions, I'll give them a shot.

Edited April 5, 2021 by TheDude123