When making a subD cone, the base diameter is smaller than the value that is assigned.
This looks like a bug to me. subdcone.3dm (4.1 MB)
Here are the steps I followed to make subD cones (truncated in this case)
1- Use the command of subDtruncatedcone and start the cone base diameter as 4 mm
2- Away from the base, assign any value for its height
3- Select 3 mm for the top of the cone
the base diameter is 4mm
the base is less than 4 mm
For comparison, I prepared a file that includes a subDcynlinder and a few types of subD cones. All of the shapes should have 4 mm as their base diameter, but only the cylinder fills up the cavity as designed.
- subD cylinder (with a 4mm diameter base)
- subD cone (smaller than 4 mm dia base)
- subD truncated cone with tri face (smaller than 4 mm dia base)
- subD truncated cone with quad face (smaller than 4 mm dia base)
I used the tab key to exam each subD shape. It shows the relationship between the subD polygon (the representation of a subD shape viewed with a tab) and the base round. The relationship is right in the case of subDcylinder but wrong in the case of subD cone.
The polygon shape should enclose entirely the base circle, not be enclosed by the circle.
For subDCones (and also subDtruncatedcones), the relationship between the subD polygon and the base diameter is reversed, causing the base to be smaller.
Please see the screen shots regarding the relationship between the subD tab viewed polygon and base round: