divide multipoint polygon

[Nerox]

Hi,

This is part of a attempt to procedurally generate better inside geometry for multi boolean operations (Breaking things apart), whitout exploding geometry or undesired effects

I'm trying to divide a multipoint (>4) polygon in a proper way, without changing the number of point on the outer ring or changing there position.

I use a cookie SOP (using the creases option) to get a single polygon which fit the cut edge.

The problem is (if you look at the images), if I'll use a convert sop to convert it to nurbs (using the hull option) and then convert it to polygons, on sides which bend in a little there appear thin overlap polygons. I've red outlined it on the polygons image.

Basically I would like to fill the single polygon with a more dense mesh, but without drawing outside the lines (Primairy school stuff ;-).

Any suggestions?

I've attached the single polygon which causes trouble.

Polygon_01.bgeo.zip

[SpencerL]

Hi,

This is part of a attempt to procedurally generate better inside geometry for multi boolean operations (Breaking things apart), whitout exploding geometry or undesired effects

I'm trying to divide a multipoint (>4) polygon in a proper way, without changing the number of point on the outer ring or changing there position.

I use a cookie SOP (using the creases option) to get a single polygon which fit the cut edge.

The problem is (if you look at the images), if I'll use a convert sop to convert it to nurbs (using the hull option) and then convert it to polygons, on sides which bend in a little there appear thin overlap polygons. I've red outlined it on the polygons image.

Basically I would like to fill the single polygon with a more dense mesh, but without drawing outside the lines (Primairy school stuff ;-).

Any suggestions?

I've attached the single polygon which causes trouble.

have a look at the Divide SOP and turn on Bricker Polys to get some more divisions.

[sibarrick]

have a look at the Divide SOP and turn on Bricker Polys to get some more divisions.

Bricker will introduce extra points in the boundary though. This is not an easy thing to do automatically without getting any artifacts.

[SpencerL]

Bricker will introduce extra points in the boundary though. This is not an easy thing to do automatically without getting any artifacts.

ah, i mis-read...yeah, kind of a nightmare. Off the top of my head, you could group those extra pts created on that edge and then move them to the nearest existing edge point. It will result in a bunch of triangles merging together at the same point and as Sibarrick said, it will introduce artifacts.

Bottom line, if you want to add faces/density to your geo then you have to add pts. There is no getting around that. Is there a reason why you cant add pts?

[edward]

Nerox, if you have a polygon that can be projected into 2D, then the Triangulate2D SOP is your friend.

[Nerox]

Well the point is that the break sop / default cookie works well for 1 or 2 slices, but it intoduces so much polygons that artifacts are introduced when you try to split a object cross wise in let's say 12 pieces.

Bottom line is that I'm trying to produce better cut geometry which in a ideal world results in geometry with correct or close edgeloops and stuff.

I'm willing to drop the edgeloop stuff for a cut geo which doesn't intoduce additional points around the edge so the a or b side can be point fused with the cut geo. Like the 'polygons.png' image but without the artifacts.

Idea behind is that it should be usable as a hero object and rendereble as subD in Maya.

Edited April 12, 2009 by Nerox

[Nerox]

ah, i mis-read...yeah, kind of a nightmare. Off the top of my head, you could group those extra pts created on that edge and then move them to the nearest existing edge point. It will result in a bunch of triangles merging together at the same point and as Sibarrick said, it will introduce artifacts.

Bottom line, if you want to add faces/density to your geo then you have to add pts. There is no getting around that. Is there a reason why you cant add pts?

SpencerL,

From a practical point of view how would you solve the 'snapping new points to the closed existing point' ?

I've attached the scene I'm currently working on, just follow the red net-boxes and you'll end up on the location where fun starts. (Don't be disappointed it's just a single multi point polygon ;-)

ice_V04_odforce.hipnc

[sibarrick]

SpencerL,

From a practical point of view how would you solve the 'snapping new points to the closed existing point' ?

You can make a group of edge points, and also extract the edge of the other half using the divide sop -> remove shared edges, then with the fuse sop snap the group to the extracted edges and final fuse to remove extra points. i think the only issue with this method is sometimes you get nasty triangles doing this method.

[Nerox]

You can make a group of edge points, and also extract the edge of the other half using the divide sop -> remove shared edges, then with the fuse sop snap the group to the extracted edges and final fuse to remove extra points. i think the only issue with this method is sometimes you get nasty triangles doing this method.

I do understand the theory behind this, and it sounds very promosing. But how do you get these additional points to snap to the closed initial point?

As you can see in the attached file, I've tried to move a point group from one object to the other. But it seems they're point number sensitive and since the brickered object has more points the group trick doesn't seem to work.

On top of that how would you manage the fuse sop to only snap points from group A to points of group B?

ice_V051_odforce.hipnc

Edited April 15, 2009 by Nerox

[sibarrick]

Sorry, the method I was thinking of relies on using my snapTo sop which takes a second input, of course the fuse sop doesn't allow for that... there must be another way though. Thinking hat is on.