Diagnosing Issues with Face Geometry?

Hi all,

I am having trouble with some face geometry in Rhino/GH and I wonder if anyone has any suggestions on best-practice for diagnosing / repairing geometry in Rhino/GH?


I have some normal Breps in Rhino (all closed) which I’m using to generate HB-Rooms using HB Room from Solid:

Nothing too crazy. Off-axis for sure, but not very complex. All planar - should be no curves or anything like that.

When I pass these Breps to the HB-Room maker, I get a bunch of ‘new’ points added to one part of the Breps:

So then all these new points are creating problems later on for some other stuff I’m doing. That part isn’t really important here though.


So I assume that the HB-Room maker is adding these points for some reason due to some curvature or something or other that I can’t see in my Rhino scene (maybe?)?

I guess my question is: how I can best ‘see’ and diagnose these sorts of geometry issues during my model creation process? I am happy to correct / edit the geometry, if I can just somehow tell whats happening, and why? From everything I can see in the Rhino geometry, its all just normal planar-surfaces and normal brep-edges… so nothing to indicate to me that any ‘new’ points would need to be added to capture the geometry in this case?

Has anyone ever figured out a good ‘diagnosis’ method for these sorts of things? I suppose that one solution is probably to use the various Pollination fixit commands and PO-Rhino tool? But I’m curious about any native Rhino tools or workflows that folks have found to help manage these types of Rhino-geometry issues?


  • Macbook 2021, Apple M1 Max
  • macOS Ventura 13.6.1 (22G313)
  • Rhino Version 7 (7.34.23267.11002, 2023-09-24)
  • LBT-GH v1.6.33
  • RH-Units: Meters
  • RH-Tolerance: 0.001

Example file attached for reference.

Any thoughts or suggestions are much appreciated.

troubled_geometry.gh (78.4 KB)

I baked your geom and used the pollination tools to recreate the model. then extracted the model vertices in grasshopper. it appears that the offending verts are not present.
Unsure why there would be a difference between the two methodologies.

also here is a hbjson of the ‘clean’ model
hopefully_untroubled.hbjson (122.2 KB)


Thanks @TrevorFedyna , good to know the PO Rhino tools, manage these faces well at least.

When I baked that specific geometry out the face-weirdness became apparent: for the ‘bad’ surfaces with those extra vertices, there were additional V curves for some reason, even though there were only 4 control points and the surface was planar. I don’t know enough about Rhino geometry to know why/how that happened… but that seems to have been the issue in this case.

Baked Geometry with ‘bad’ surface selected:

Only 4 Control Points, but 5 V-Curves:

So for this type of face error (not really en ‘error’ I guess, just an ‘issue’), just rebuilding the surfaces before sending along to the HB-Room-Builder seems to remedy the issue in my case here. So something simple like:


troubled_geometry_w_fix.gh (93.5 KB)

1 Like