Group the result of a subdivision

[Luijee]

Hi all,

Consider you have a line made from 2 points. You subdivide the line to give you a new point in the middle, how can you add this new point to its own group?

As a bonus, how could you group the resulting geo of any SOP?

[BRZ32]

If you group the geometry before the subdivision you can use the combine tab of the group node to group the inverse (not equal =/=) that initial group. That should give you a group with only the new points.

[Luijee]

18 hours ago, BRZ32 said:

If you group the geometry before the subdivision you can use the combine tab of the group node to group the inverse (not equal =/=) that initial group. That should give you a group with only the new points.

Inverting the group won't work since the new point created from subdivision inherits the existing group. Is that what you meant?

[mine]

Maybe "group transfer" playing with distance threshold?

Or maybe if subdivide doesn't change ptnum you can write a wrangle (or a VOP) running it on original geo points to assign points of geo2 into the group based on ptnum?

 

[f1480187]

@Luijee, it works for me. It doesn't propagate point groups on new points.

 

group_new_points.hipnc

[3dome]

creating detail attrib with number of points before subd and grouping after subd based on expression works for me with Houdini Catmull Clark.

Tested on simple grid only

//detail wrangle

i@max = @numpt - 1;

 

//groupSOP

@ptnum > @max

 

[Luijee]

21 minutes ago, f1480187 said:

@Luijee, it works for me. It doesn't propagate point groups on new points.

49 minutes ago, 3dome said:

creating detail attrib with number of points before subd and grouping after subd based on expression works for me with Houdini Catmull Clark.

Looks like it works for polygon geometry but not for polylines, guess it propagates point groups based on its primitives?

I'm taking every odd point in the polyline as it works for what I need, but would be nice if there was a proper reliable method.

 

group_new_points_line.hipnc

[f1480187]

@Luijee, try Edge Divide node instead of Subdivide.

group_new_points_line_edgedivide.hipnc

Edited June 29, 2016 by f1480187

[Luijee]

Does the job, thanks!