# SUBD vs Tspline _ geometrical differences

(B Design Bg2) #21

I saw it,but my idea is to implement somewhat of a hybrid between proportional and offset edge insertion. This way, the user gets the ability to have an offset edge insertion everywhere except the very low and bottom of this cube that you used as an example, without worrying that there will be any self-intersection. The current offset mode shown in your animated screencast creates self-intersections. This is why I mentioned maintaining a custom offset distance on the opposite side that will prevent self-intersections like this.

(Nathan 'jesterKing' Letwory) #22

I’m not sure I follow, that is what proportional does…

(B Design Bg2) #23

The proportional option will not insert new row of vertical edges to this ball model with equal offset. In my image example, the hybrid mode works as offset in any area except those areas where the newly added row of edges would cause self-intersection. This is why the idea for the hybrid mode works with a secondary offset at the opposite side, so that it prevents any self-intersection.

I will explain that using my example image. If X=20 mm offset, Y=18 mm secondary offset, Z is a transitional distance where its edge is 20 mm from the left efge (just like X) while also being 18 mm away from the opposite edge (like Y).

Another example here:

#24

The reference to TSplines is very strong for the development of SubD in Rhino: it was for a long time the only real plug-in to generate subdivision surfaces. Therefore we should look at some important initial command. For example, Rhino lacks a handy command that allows you to select and choose vertexes, edges or faces (with the keyboard it’s not always comfortable). And then, it would take a command equivalent to “Smooth toggle”, so you can work on the basic geometry. There are still many other tools like: “Geometric solid”, “Extrude curves, edges ad faces”, “Insert edge and point”, “Subdivide faces”, “Match”, “Bridge”, “Thicken”, etc.
We’ll see later …
Moreover, not of little importance, it is hoped that Rhino does not become only SubD and Grasshopper, as the Nurbs modeling tools would need a healthy regenerated and enhanced, especially in editing.