Group based on faceting or "phong break"

[Janmansilver]

In the group sop one can group based on normal direction, but this is mostly from a "planer looking in/at perspective" with the possibility of degree of spread, but I find it much more helpful if one could create groups based on selecting a surface which is "smoothly connected" - to understand what I mean try looking as this: 

Another way of putting it would be a procedural way of selecting primitive surfaces which comprise a smooth logical part before a hard edge/break.

[CTEffects]

There are a few ways of doing this, depending on what you are looking to do.

The naive approach is to just use the min angle parameter in the group sop in the edges tab.Though there is no guarantee that your selection will perfectly match where the normal breaks are.

A smarter way would be to first put any existing boundary edges in a group, vertexsplit based on N, group all of the new boundary edges and subtract the original group to get just the new split edges, then just group transfer back to the original topology.

Also, If you are looking to group islands of smoothly-connected prims (like in 3dsmax), you can simply use a connectivity SOP after the vertexsplit, and copy the connectivity attribute back onto the primitives of the original.

I've included an example file that uses all of the techniques mentioned above.

group_cusped_edges.hip

Edited September 7, 2016 by CTEffects