Say I have some interconnected curves (or points/particles) and I want to give them thickness by wrapping them with a mesh. How would I go about it?

Blocking out with basic meshes and smoothing comes to mind. Or isosurfacing. Both should be possible in Houdini but how?

Or, perhaps, an equivalent of this can be attempted?

http://3daliens.com/joomla/index.php?option=com_content&view=article&id=51:pwrappermaxmaya&catid=36:products&Itemid=55 [3daliens.com]

Thank you for the ideas and advice.

Have you looked at the particle fluid surface node? That should give you a similar result to pwrapper. You might want to try resampling the curve, copying polygon circles onto it and skinning them though, that should give the desired effect. Here's an example file with both methods.

Thanks. I am looking at the fluid surface as advised. Had a look at the example too. I should have explained better. The ambition is to produce considerably more complex topologies.

E.g., have a look here: http://n-e-r-v-o-u-s.com/cellCycle/index.php [n-e-r-v-o-u-s.com]

Not from lines but similar to the cellular geometry to what I had in mind…

Or here:

I see that using particle fluid surface one can come pretty close (at least with one curve). Here it is with meatballs an option and 2 subdivision. However, it would be great to relax this geometry. E.g., by making polygons tend towards planarity and even sizes, like here:

see Combined_mesh_optimization_demo

http://www.grasshopper3d.com/group/kangaroo/page/example-files [grasshopper3d.com]

if you have no access to the software, here is something using the same ideas for a somewhat different/related purposes:

http://www.youtube.com/watch?v=M2AgX_W6dTY [youtube.com]

Thanks for further suggestions.

Hmm, sounds like you're after the Polywire sop. Polywire with a Subdivide can yield some pretty cool results.

Ah, great. This is nice. Looking at the Polywire example in Help, changing widths (via alpha?) is a bit of a hack (or is it just my ignorance?).

How would I go about automating the width assignment? Say, influenced by the distance from some arbitrary point(s) for starters? Given that this is for learning, I am curious to know the workflow with interface scripts, VOPs, Python SOPs, if anybody feels so generous.

Thank you.

Hey jchor

Many Houdini parameters support attribute variables such as color or alpha of the point, so i would not say it is a hack . However, if you do not want to use alpha, try this:

- create your geometry that has the wire cage you want for the poly wire. (IE a sphere)

- create a new point attribute via attributeCreate, call it something like thicknessMultiplier, and set the default value to 1

- use an operator such as edgeDivide or divide to get the dual of your geometry (IE the midpoint of every edge). Some of the operators may allow you to group your new points. If not, wire a group SOP and group new points with an expression (IE number of neighbors = 2)

- set your thickness multiplier attribute to all the new points on your group to 0.5 (point SOP)

-put a poly wire node and set the wire thickness attribute to whatever your thicknessMultiplier attribute was (IE $THICKNESSMULTIPLIER). You can also play with the expression to give a little randomness (IE $THICKNESSMULTIPLIER*rand($PT))

- play with the thickness multiplie value in the attributeCreate and point sop to adjust result (you can even expose the parameters in a digital asset so that they are in one place)

-alternatively, try also the wireframe sop as it handles curve branches

I am not in front of my computer now so I cannot provide an example. :p. Hope this helps

Alternatively, if you want to learn vops, try using a VOP SOP to get the point neighbors, and put them in a group . Check out the nodes under the geometry folder in the VOP SOP tab menu (neighbor count, add to group, etc)

One of the nice things about Houdini is that there are many ways to solve a problem . I personally try to go as far as I can with nodes before I script

Not sure it is a good idea to bring to life an old post but it is somewhat relevant…

If I want to relax a mesh, how do I go about it in Houdini? Here is the result of the Relax modifier in 3Ds MAX (and this is what I am after). In Houdini, Smooth does not do it if I use a mesh box. What am I missing?

Thanks.

j.chor.r
What am I missing?

Subdivide SOP, preceded by a Crease SOP if you wish to control the edge weighting.

BTW, did you get any cool geometry out of the original effort in this post?
Would be nice to see

Hm… Thanks. But in the image I posted the cube and the relaxed mesh have the same number of polygons.

I actually managed to make things work In Houdini by changing connectivity of the Polygon mesh to Triangles. Seems the same as Relax in MAX then, only some rippling around corners…

As for the geometry from the original post. Yes, it is somewhere. But only in sketches… So, never made it here.

j.chor.r
Hm… Thanks. But in the image I posted the cube and the relaxed mesh have the same number of polygons.

Wrong.

You are indeed looking at a crap load of polys on the smoothed result in the viewport. OpenGL or DirectX is certainly chopping up the box with the subdivide operation applied and then tessellated and displayed on the graphics card.

Just because they display the original hulls on to the subdivided mesh on the limit surface does not mean that you are looking at 6 polygonal faces. You are looking at the projected original hulls on the subdivision limit surface which depending on the level of detail of the viewport, a crap load of polys.

Houdini currently can not display the limit surface of sub-d's. If it could, then you could recreate this without the use of Mantra to render the sub-d limit surface.

Sorry for the belated reply. My use of Houdini is very sporadic.

But I am not wrong (never! - ). This operation is not sub-d.

The original cube in my image from MAX has *the same number of faces* as its relaxed (not sub-divided) version. I made it myself, I should know. Both have lots of polygons, yes.

The “relaxing”operation does not modify topology.

Gotcha. Most vids/pics for Max use the shaded wireframe mode which would have helped here.

I did a quick search on the relax modifier only to find out that it's a tool that has as many -ves as +ves. There is a tool added as a 3rd party plug-in called Topo-Relax which you may want to look in to.

As far as Houdini is concerned, when you look to iterative smoothing of points (max refers to these as vertex) attriubtes, try the Smooth SOP first.

The Smooth SOP seems to work quitie similar to the Topo-Relax plug-in. It defaults to smooth P or position but you can smooth any attribute including uv's. It is worth a try to see if it can remove ripples on surfaces.

I attached a file working up a few Smooth SOP scenarios. It does an ok job of the polygonized/cookied/faceted raw teapot btw.