How to extract a clean curves from a SOP clip cut ?

[sebkaine]

Hi Guys,

I want to extract the intersection curves of 2 polygon mesh.

I get correct result with the SOP cookie > crease option, but it is slow and base on a node i don't trust that much ...

I would like to replicate this by using a SOP clip, i have suceed to extract the section i want , but i am struggling to extract a clean curves from this,

If you have any idea that would be great !

Thanks for your time !

E

 

curve_from_cut.hiplc

[papicrunch]

divide with remove shared edge ?

[NNois]

ok sorry to intercept this guys but, i was searching this for a long time now, how on hell you can fiund "delete edges but keep boundary ones" in "Divide SOP" ??? 50% of tools in houdini are spreads over toons of SOPs with not so desciptive name.

Do someone ever wrote a SOP Visual Guide or something ???

[f1480187]

Here is how to fix Divide SOP limitation about open geometry:

// Point Wrangle.

#define ALMOST_ZERO 1e-6

vector4 plane = chv("../clip2/dir");
plane.w = ch("../clip2/dist");

float dist = abs(@P.x * plane.x + @P.y * plane.y + @P.z * plane.z - plane.w);
if (dist > ALMOST_ZERO)
{
    removepoint(0, @ptnum);
}

And with it, it should be really fail-proof solution, comparing with Cookie SOP. But in 15.5 there is a new Dissolve SOP which able to create curves from edges, and it works quite good, much better than old one. Give it a try also, if you are up to date.

edge_to_curve.hipnc

 

@NNois, I agree, many nodes have such "side features", like Facet's removing inline points by threshold or Divide's removing shared edges. I believe it is what you could get from the main algorithms for free. If you do something like shaders or VEX wrangles, you might notice that you could compute a lot of auxiliary and potentially useful data by outputting inner variables.

[sebkaine]

Thanks a lot for all your very useful answers guys ! This one was sneaky ...

I have assemble a hip that sum up all the methods ...

 

I would also be curious to know how to do this in NURBS in Houdini , cause it was pretty obvious to me that this would be very straightforward ,

you have 2 nurbs patch and you just want to isolate the intersected isoparm , but i fail to use SOP surfsect correctly , i only get ugly stuff.

I might be responsable for that anyway ...

 

Cheers

E 

test_cut_02.hiplc

[sebkaine]

i have edited the file with the nurbs technics, but nurbs is slow and also not as good as clip ... 

f1480187 your technics with clip > divide > wrangle look to be the best imo as it is not 15.5 depdendant ...

 

 

test_cut_03.hiplc