How to generate clean poly curves out of an Edge Loop?

   11285   10   1
User Avatar
Member
700 posts
Joined: 3月 2009
Offline
Hi

I've been trying different solutions for a couple of days, but nothing works completely. My original geometry doesn't have clean, nicely ordered point numbers, so when I extract an edge loop using the disolve SOP the points are randomly ordered and it's tough to process them afterwards.

Firstly, I need to extract two parallel edge loops out of a pipe-like geo and bridge them to form a single-sided tape that I can run through sims. Besides the point ordering issue, whenever I extract the edge loops (which appear to be valid polygon curves) I find that they have twice as many vertexes as points :shock:. There's no operation I can do to fix that and even the clean SOP doesn't do the job properly, it always invisibly breaks the “curve” and I can't loft the curves properly.

I'm open for new ideas at this point, as long as I don't have to use the HDK…

Cheers
Toronto - ON
My Houdini playground [renderfarm.tumblr.com]
“As technology advances, the rendering time remains constant.”
User Avatar
Member
8839 posts
Joined: 7月 2007
Offline
sort it by vertex order and use good old Add SOP to recreate curve

Attachments:
curve_from_edgeloop.hip (54.5 KB)

Tomas Slancik
FX Supervisor
Method Studios, NY
User Avatar
Member
700 posts
Joined: 3月 2009
Offline
tamte
sort it by vertex order and use good old Add SOP to recreate curve

Thanks, Tamte, although I have tried that and it didn't really work cause of the intrinsically messed up geometry that I have to work with. when I try to sort by vertex it still doesn't work as I would expect…

I'm posting a piece of the geo, in case you have a chance to look at it.

Cheers

Attachments:
messed_up_geo.hip (66.7 KB)

Toronto - ON
My Houdini playground [renderfarm.tumblr.com]
“As technology advances, the rendering time remains constant.”
User Avatar
Member
4271 posts
Joined: 7月 2005
Offline
rafaels
Thanks, Tamte, although I have tried that and it didn't really work cause of the intrinsically messed up geometry that I have to work with. when I try to sort by vertex it still doesn't work as I would expect…

I'm posting a piece of the geo, in case you have a chance to look at it.

If its always going to be a Tube shape then just use a MatchTopology SOP ahead of time to sort the points into a reasonable order, then you can use all sorts of lovely SOPs to get an edge loop.
if(coffees<2,round(float),float)
User Avatar
Member
700 posts
Joined: 3月 2009
Offline
Cool! Here's one SOP I've never known existed. ops:
It solves 99% of my problems now…

Thanks
Toronto - ON
My Houdini playground [renderfarm.tumblr.com]
“As technology advances, the rendering time remains constant.”
User Avatar
Member
4271 posts
Joined: 7月 2005
Offline
rafaels
Cool! Here's one SOP I've never known existed. ops:
It solves 99% of my problems now…

Thanks

Coincidentally the FX team here used this same technique last week to solve a similar problem, I attached the setup into your file.

Attachments:
yarp.hip (74.3 KB)

if(coffees<2,round(float),float)
User Avatar
Member
606 posts
Joined: 5月 2007
Offline
I'm not completely certain what your topology looks like, but I've fixed tube-like point orders by applying a cylindrical uvtexture and then putting $MAPU in Sort SOP's expression field.

For nasty cases you might lay down a spline, sweep a circle or use polywire, transfer UVs, and do the above. Maybe with some raying for good measure

edit: ohh, I missed a lot of replies :)
User Avatar
Member
330 posts
Joined: 7月 2007
Offline
rafaels
..

I'm posting a piece of the geo, in case you have a chance to look at it.

..

the attached file doesnt seem to have any geo ‘data’ inside .. even Locked .
except the things that cannot be seen , nothing is like it seems .
User Avatar
Member
700 posts
Joined: 3月 2009
Offline
Wolfwood
Coincidentally the FX team here used this same technique last week to solve a similar problem, I attached the setup into your file.

Now I know…

Cheers
Toronto - ON
My Houdini playground [renderfarm.tumblr.com]
“As technology advances, the rendering time remains constant.”
User Avatar
Member
4271 posts
Joined: 7月 2005
Offline
zarti
rafaels
..

I'm posting a piece of the geo, in case you have a chance to look at it.

..

the attached file doesnt seem to have any geo ‘data’ inside .. even Locked .

Its a Houdini 12.0 file, so if you are trying to open it in H11 that might be the problem.

But if you are in 12.0 I have no idea.
if(coffees<2,round(float),float)
User Avatar
Member
330 posts
Joined: 7月 2007
Offline
Wolfwood
zarti
rafaels
..

I'm posting a piece of the geo, in case you have a chance to look at it.

..

the attached file doesnt seem to have any geo ‘data’ inside .. even Locked .

Its a Houdini 12.0 file, so if you are trying to open it in H11 that might be the problem.

But if you are in 12.0 I have no idea.

yep , i thought that too , after downloading your file .

anyway , something like that shoudnt happen ..




.cheers
except the things that cannot be seen , nothing is like it seems .
  • Quick Links