### group fused points

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Hi!
Is there any method to create a group of points, that have been fused by fuse point?

So I've got geometry, I create a fuse sop and all points, that have been fused with other points will be in this group?

(my only idea is to remember positions of points as attributes and after fusion check if they have been changed - but it would not work if I fuse points that are in the same position )

I hope there is a method to do it
thank you
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you are not far from the solution

fuse SOP by default fuses one point to another and therefore only one changes position and that gets deleted so there is no difference in remaining points

but fuse SOP in Snap mode snaps points within treshold together moving them all, for example to average position
then you can group only moved points
then apply fuse with very low treshold to fuse just snapped points
the group will be still valid

here is the example

Attachments:
group_fused.hip (68.1 KB)

Tomas Slancik
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Method Studios, NY
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I've attached another way to do it. The first is relatively straightforward and uses the topology of the geometry pre- and post-fusing to create the group. Basically you calculate the number of primitives for each point before and after the fuse, and the points where that number has changed represent the points that have been fused.

This only works for points that are part of primitives; i.e. not raw points, so I also put a “stupid Houdini tricks” way of dealing with just points.

This works by creating both integer and float attributes that store the original point number for each point. When fusing two or more points together, Houdini updates float attributes with the average of all the fused points. With integer attributes it chooses whichever value is on the lowest point number. So any point where the integer and float attribute values differ has been fused.

Attachments:
group_after_fuse.hip (55.9 KB)

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tamte - thank you! I was making something similar to yours idea unfortunately it doesn't work for points, that are on the beginning in the same place (so theyrs place isn'tchanged and the're fused)

johner - thank you! your ideas (especially this one with float attributes) are brilliant. I didn't know about this float attributes. Thank you!

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I know that this is very stupid, question, so I will not add new topic and I'll post it here - could you please tell me, what is the difference in houdini between point and vertex?
(when I was looking at johner sollution, I saw, that when the vertex attribute is promoted to point attribute it sums all edges going to this vertex - and I don't completely understeand why it behaves so :roll: )
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Not so stupid as there is a constant confusion about these two in 3d world because some apps don't make any distinction here (at least in gui). Vertex is a “corner” of a polygon, whereas point is location in space. Vertex belongs to a polygon and is attached to a point. Houdini allows to store attributes per every vertex, which means its values won't be interpolated between polygons sharing the same point. In fact some of the attributes don't make much sense not being vertices'. Normals and uvs as long as serve rendering purpose, should be vertex attributes for example.
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Thank you SYmek Now it's clear