[Sidefx-houdini-list] fracturing a grid with polygonal curves?

Andrew D Lyons tstexture at gmail.com
Fri Aug 24 16:27:12 EDT 2007

You could use your curves as a cookie cutter. Here's some ideas:

The cookie sop requires that cutter objects define some kind of
volume. You would need to make your curves into a loop of some sort,
and then extrude that along the vector towards the point (5). (I think
the vex flow normals Sop formerly on odforce allowed you to create a
transverse vector perpendicular to an edge.)

With a cookie built, a cookie sop can be used to isolate the areas
defined by the curve. You'll need to set up some kind of a loop SOP
(H9) so that you can build a cutter and make a cut using each curve.

To find which output prim has the point(5), first apply a point attr
to point(5), and then use attr transfer to transfer the attr to the
shapes. Use Sort SOP using sort prims by expression to make the prim
nearest the point(5) prim zero. Delete non-selected Prim 0. Use
connectivity if the shape has more than1 poly.

Something like that should do it, but I'm sure there are other ways.


On 24/08/07, Darran Edmundson <darran at edmstudio.com> wrote:
> Any ideas on the following:
> 0) In the viewport, go into Top view.
> 1) Lay down a Grid SOP.
> 2) Lay down a Curve SOP. Draw an open polygonal curve that snakes across
> the grid. Endpoints of the curve cannot lie inside the grid.
> 3) Repeat step 2) any number of times.
> 4) Merge the curves.
> 5) Lay down an Add SOP with a single point that lies within the grid.
> The aim is to procedurally extract from the grid the unique polygon
> clipped by the various curves (4) that contains the point (5).
> Cheers,
> Darran.
> --
> Darran Edmundson [darran at edmstudio.com]
> http://www.edmstudio.com
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Andrew D Lyons | Digital Artist | http://www.tstex.com

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