Can I get a group from PolyCap?

[spectronaut]

Is there a way to define a group of primitives based off the faces created by PolyCap?

[Atom]

Just think of it as subtracting the input from the result.

ap_group_polycap_faces.hipnc

[spectronaut]

Thank you, again. So helpful. 
I am slowly getting the Houdini mindset thanks to excellent people like yourself. Very much appreciated. 

[acey195]

a way to group it with less nodes and without splitting it after the polycap is by grouping by range:

so tube1 -> polycap_AddsMoreFaces -> Group_by_range:

in the group by range, make the range: nprims("../tube") to $N

it basically uses the heuristic that the primitive numbers of the polyCap always go after the input geometry.

[galagast]

Neat trick acey!

I added a file with 3 samples using attributes/wrangles:
1. Using acey's trick above.
2. Using an attribute to tag primitives faces before being capped. Then using group expression to isolate by the tag id number.
3. Using attribute wrangle, almost similar to acey's method. It reads the primitive count of the tube, then grouping only primitives that has newer primitive numbers.

 

 

polycap_groups.hiplc

[konstantin magnus]

You can also type

$NVTX > 4

as an expression in your group node, if your caps have more than four corners.

Edited January 11, 2017 by konstantin magnus