String Character

[breadbox]

I have a base mesh of a character that I created in Maya. I bring the OBJ into houdini and I am trying to figure out what is the best way... or any way to sort of wind a curve around the body.

Im not sure that Ill need to do one continuous path, it can probably just be a bunch of edgeloops essentially.

anyone know any tips for turning edgeloops in one direction into curves? or if there is a better alternative way? I was also thinking of turning the mesh into a metaball mesh or an ISO surface and somehow sectionting it with convert Meta?

[pclaes]

I would do it the following way:

1) build some approximation tubes (nurbs) around your character. -> an arm becomes a line with enough subdivisions to cover the detail. You copy circles on the line, you skin the circles.

2) use the creep sop to creep your lines onto the nurbs cylinder. (creep gives fairly nice deformations)

3) use the ray sop to ray the lines onto the mesh. -- you can use that original line (ie. at the center of the arm) as a pointcloud lookup to get the normals to point towards the mesh.

*) it's kinda like making a stick figure of your character. Turning all the lines in tubes. Creeping more lines on the tubes which will give you the approximated wire character and then refining with the ray sop. Probably identifying problem areas (elbows, shoulders, neck) and blending them based on stretch/density/length attributes vs the rest position. (like a pose deformer, but procedurally).

[breadbox]

oh wow super. O.K I'm almost there! One thing I cant figure out is how to get the normals from the creep curve projected inward TOWARD the mesh. by default the points on a curve don't have normal information. You mentioned to use the original curve as a 'pointcloud'. I sort of understand what you mean. I can take the points on the outer curve and point them in to the nearest point on the skeleton curve, however I'm not sure what nodes to use and how to connect them?

StringMan.zip

[Macha]

Try to set the method to Minimum Distance.

[breadbox]

I ended up using the CHOPS method from this link

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=94871&sid=2db61fce35e3de204d21aedfd639ab59

But id still like to know how to do a point cloud from a central curve and point all the normals in that direction. just for future.

ah ok cool minimum distance works pretty well also, but it is nice to be able to control the ray through the normals.

[pclaes]

I added the pointcloud lookup and another way with the facet sop and attribute transfer.

I recently read somewhere the polyframe tangentu and normal could be used similarly to the tangent sop.

[Macha]

But id still like to know how to do a point cloud from a central curve and point all the normals in that direction. just for future.

Find the nearest/average_nearest point and then subtract the positions, normalize and you have a direction vector.

The raysop is of course more sophisticated than this. It finds nearest primitive intersections and does it more cleverly.

Edited January 6, 2011 by Macha

[pclaes]

I added the pointcloud lookup and another way with the facet sop and attribute transfer.

I recently read somewhere the polyframe tangentu and normal could be used similarly to the tangent sop.

it would have helped if I actually remembered to attach the file...

StringMan_02.hip

[Macha]

Because I have some time waiting for a sim... here is a simplified vopsop version of the raysop function!

Red ball is projected onto wavy blue surface. Press play to see it animated.

intersect.hip

Edited January 7, 2011 by Macha

[breadbox]

Super Thanks for the help peter and macha. the final turned out pretty good.

[pclaes]

Looking pretty cool!

I think everything fits except for his toes. They seem to be a bit inconsistent with the rest. Perhaps replacing them with needlepins/thumbtacks would work. Or give him one leg that is "broken" -> protected by one of those metal tiny buckets you put over your finger to protect it so you don't sting yourself. (I don't know what they are called, but this is what I mean: http://t3.gstatic.com/images?q=tbn:ANd9GcSF_Uk0qo018ucMOIyD_VmwDp3XcvqQaqnH2QHHfWe1CSiFj6CM ) - it could give him some more character, kinda like a pirate captain with a wooden leg. I like the assymetry of the character.

Perhaps a bit more noise here and there in the wires could help. Also have a look at this thread as it shows what you can do when varying the curve that is used for creeping:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=21231

You could even consider creeping new curves around the curves you crept before (they'll probably need to be nurbs cylinders for it to work which will make it heavy). It would make your current curves look like they were made out of even finer curves (which is often the case if you look close up at a wire) - but perhaps you want to do this in textures rather than geometry.

[breadbox]

ah yea that would be great! I think they are called a thimble. I might just have to do that. I was considering doing another helix wrap around the projected curves to do a really high res string look, but i figured it would not be necessary and might be better to do that in a texture. maybe ill give one a try just cause now i got the building blocks to do it.