Procedural ways to select edges?

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Hi everybody,

It seems quite impossible to do edge selection on a procedural basis. Am I overlooking something? Because it is something very essential to have.

I'm unable to find anything of it in the doc's.

Like selecting edges depending on the angle.
Or selecting by index number etc..

Cheers
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No, there isn't, and I'm not too sure how essential it is In Houdini. An edge doesn't seem to mean anything in Houdini, just a line between points, it has no ID and no attributes The few edge tools that do exist seem to actually work on point selections. Do you have something in particular in mind you are trying to work out? I'm sure there's likely a way to go about it using points and a little math.
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The problem start when you want to procedurally create an edge group then pump that into a sop that only deals with edges.
Because the “edge” sops use syntax like 17e0:1 it all gets a bit tricky. I feel your pain, but can't actually help.
However you may be lucky and as MichaelC says it may be that in your particular case there is a solution.
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Simon
The problem start when you want to procedurally create an edge group then pump that into a sop that only deals with edges.
Because the “edge” sops use syntax like 17e0:1 it all gets a bit tricky. I feel your pain, but can't actually help.
However you may be lucky and as MichaelC says it may be that in your particular case there is a solution.

I would have liked to use it with the polybevel for rounding edges.

It gives different results if you have a point selection. And I find it at the moment too hard to create an expression that can create a string needed for an edge selection.
Because if not done properly it can select unwanted edges.
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To specify an edge selection rather than a point selection in something like the polybevel SOP, you'd specify p<PT1>-<PT2>. PT1 and PT2 being the indecies of the two points that define the edge. I think if you can figure out how to select and sort the points you want in VEX, you can probably use the string functions in Houdini to format the edge selection string you want for the Polybevel tool.

It'll probably make for a slow SOP, you may even have to go out to the system to sort, but I think it can be done depending on what edges you are wanting to select. Maybe it could be implemeted in the HDK…
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Maybe worth putting in a rfe for the polybevel tool to support an option to round edges based on a cusp angle. Much easier to do it all internally.

Another thought would be to create a generic sop that can process point groups and output the correct syntax for an edge group straight into the group field of the sop you need it for. This would be an HDK thing I think since it's the only place AFAIK that you can pick up when a cook is happening.
I rfe'd a “on cook” event script for hda's but I don't think it has happened.

I've not tried modifying parameters on other sops based on cooks but I have done it with a user activated button….. I don't see why it wouldn't be doable though.
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FYI, now that we have the Python SOP, we can just use that:
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=103815#103815 [sidefx.com]
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took me a second to get it working with a extrude on a font or a curve. The trick I think is to check consolidate face to mesh.

Here is your modified file with the font and curve, again, a big thanks here.

Attachments:
polycuspbevel_jrh.hipnc (60.0 KB)

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