Exporting SubD objects to FBX

Rhino Developer
,
1

I have been working on a tool to convert Rhino documents into Unity scenes, in which level of detail is handled automatically. With the release of Rhino7 I would like to support SubD objects, but I having trouble finding documentation.

Q1: How can I identify a SubD object. Is there a new object type?

Q2: The FBX exporter has added “SubdivisionLevel=4 and SubdivisionContext=Absolute” - what do these options do? (Specifically, how can they be used to create varying levels of exported mesh detail?)

2

Are you using RhinoScript for this? I’m assuming you are based on the “object type” link that you sent. That page looks like it may need updating to include values for SubD. Here is an equivalent for for RhinoCommon so you can see the values
https://developer.rhino3d.com/api/RhinoCommon/html/T_Rhino_DocObjects_ObjectType.htm

3

Thank you!

I’m using PythonScript… so documentation references to RhinoScript.
The project is open source-source, so I’ll update the reference there too.

The detailed meshing documentation mentions levels now… so that’s something.

Is there documentation elsewhere that defines what “Level=4” and “Context=Absolute” means to Rhino?

4

Hi @services,

The “levels” are not documented in great detail yet. But basically:

1 = Extra Coarse Density
2 = Coarse Density
3 = Medium Density
4 = Fine Density
5 - Extra Fine Density

Fine Density for example, when interpreted as an Absolute SubD display density, each SubD quad will generate display mesh quads in a 16x16 grid and each SubD N-gon will generate N*16 display mesh quads. When a SubD has more than 2000 faces, Adaptive Fine Density is reduced to adaptive Medium Density.

Hope this helps.

– Dale

1 Like
5

Hi Dale,
Thank you for your answer!

To make sure that I understand…

  • The level corresponds to the number of division of a quad axis, so coarse → 2x2, medium → 8x8 and fine → 32x32?
  • The context is either “Absolute” or “Adaptive” (and there are no other options)? (I have verified these two, but clicking on the command text does not reveal options for me.)