De-Subdivide

[negow 0]

Seems easy enough, remove each and every edgeloop so to de-subdivide a mesh. Zbrush has a way, but having it as a node would make my life a bit easier. The subdivision is Catmull-clark based, so the must be some logic behind vertexorder and such. At least I think so.

Example.

A box (8 points) -> Subdivide (26 points) -> Edit some of the verticies, sure -> De-Subdivide (8 points)

Is there a nice way of accomplishing this?

[daniel.phillis 1]

bit of a late post, but Rob Kelly nutted this out for me.

unsubdivided_example.hipnc

Edited July 11, 2010 by daniel.phillis

[Fabiano Berlim 13]

bit of a late post, but Rob Kelly nutted this out for me.

Very smart solution!

Thanks for sharing!

[bunker 287]

Very cool technique indeed

bit of a late post, but Rob Kelly nutted this out for me.

[sparkChan 1]

bit of a late post, but Rob Kelly nutted this out for me.

thanks for your post, it is useful for me.

[fxrod 25]

This is so much nicer than polyreduce!

I have a question, though. The delete SOP is reducing every 1 out of 2 prims. Obviously, this requires a certain ordering of the polygons. I'm wondering what the sort order is on the original piece of geometry. Is it a standard modeling procedure?

[kgoossens 83]

bit of a late post, but Rob Kelly nutted this out for me.

It would be good to post this on Orbolt.

[A. Morales 6]

On 10/10/2010 at 2:49 PM, fxrod said:

This is so much nicer than polyreduce!

I have a question, though. The delete SOP is reducing every 1 out of 2 prims. Obviously, this requires a certain ordering of the polygons. I'm wondering what the sort order is on the original piece of geometry. Is it a standard modeling procedure?

fxrod did you ever manage to figure this out? 

[3dome 132]

On 4/25/2016 at 6:01 PM, A. Morales said:

fxrod did you ever manage to figure this out? 

It appears to only work with the way Maya is ordering the polys. -> works with geo coming from maya

To see the difference:

    Export a .obj cube from maya and compare point numbers/prim numbers in Houdini to a houdini box object.

    Also in maya hit "3" and convert that preview to polygons. expor that too.

    In Houdini take a box, subdivide (catmull-clark, depth = 2) and the append delete sop with "range [1 of 2]".

    Same delete sop applied to smoothed maya cube will give you the result you want while on houdini subd box it fails.

 

I yet have to find a way to reorder any geo in houdini to work with that method or change the method to work with houdini's way of ordering polys.
 

Edited June 8, 2016 by 3dome
hit enter on accident before finshing the post

[animatrix 210]

You can implement this paper which wouldn't care about point/primitive numbers.

http://wscg.zcu.cz/wscg2006/Papers_2006/Full/B89-full.pdf

[3dome 132]

yea. will do when i find time. or you switch to zbrush for that task, they have this implemented. but be sure to have a geometry as input that got its shape by subd. if you subd and then just delete a single face, the algorithm wont work