Hello,

I am cleaning up photogrammetry with the poly doctor, clean sop, and a poly fill node. I am outputting valid topology from the poly doctor, then I export out of Houdini into 3ds Max and when I export out of Max it says I have a "rats nest" in mesh. Can anyone guide me how to find "rats nests" in a mesh in Houdini and remove them procedurally?

Vincent Griffith

Hi VGriffith
I remember having lots of these when i was doing photogrammetry.
If i'm not wrong, it was because of tiny holes with intersecting geometries, and i used to fix them in zbrush, smoothing out that area and maybe using a combination of dynamesh and zrememsher.
I believe that to do that procedurally you could convert them to VDB, and convert them back to polygons.
Not sure if you need to keep that original topology intact though.
Doing this would make you lose your original UVs, but you can still bake it back after.

It all depends on what the issue is
The description "rats nest" is very vague and not informative
Is it max telling you you have garbage geo but doesn't bother specifying the actual issue?

It can be anything
- non manifold edges (including flipped polys, overlapping polys)
- duplicate vertex attachments
- degenerate primitives
- isolated points
- almost zero area prims
- intersections
- probably something else

Without your geo it's difficult to pinpoint what your specific issue is

tamte
It all depends on what the issue is
The description "rats nest" is very vague and not informative
Is it max telling you you have garbage geo but doesn't bother specifying the actual issue?

It can be anything
- non manifold edges (including flipped polys, overlapping polys)
- duplicate vertex attachments
- degenerate primitives
- isolated points
- almost zero area prims
- intersections
- probably something else

Without your geo it's difficult to pinpoint what your specific issue is

Yeah I wish Max would say what part of the geometry is actually messed up. It literally just says "Rats Nest in Mesh" and leaves it vague like that. lol! It is so beyond frustrating. I was hoping on the Houdini end there was ways of combating all the issues you were listing with the poly doctor or some node like that so 3ds Max would shut up! lol! I would love to upload the geometry but I am not allowed to.

VGriffith
I was hoping on the Houdini end there was ways of combating all the issues you were listing with the poly doctor or some node like that so 3ds Max would shut up!

There is a way for sure
But as I said you have to identify the issue first to be certain you are using the right nodes to fix it

tamte

VGriffith
I was hoping on the Houdini end there was ways of combating all the issues you were listing with the poly doctor or some node like that so 3ds Max would shut up!

There is a way for sure
But as I said you have to identify the issue first to be certain you are using the right nodes to fix it

Yeah it's tuff to find out the issue when it is a pile of triangles. Needle in the hay stack stuff. I will figure it out and report back.

VGriffith
Needle in the hay stack stuff

But you have Houdini so if you know you are looking for a needle you can find it

It's only tough if you don't know what to look for
maybe start with the things I listed

Or if you manage to export subset of your geo that still happens to be a "rats nest" and can post it here it may be easier