How do I create a line between the corresponding points of 2 curves?

[sekops]

Hi There,

Im trying to create a rig. Basically at this stage I have 2 circles, one above the other. Basically I want to create a line between each corresponding point of the other nurbs circle.

Next, I wwant to attach an object to each point of the each line, and have the objects aimed at the adjacent object. Im guessing this could be created if I create I align each object to the tangent of the line. Or... align each object to the cross product of the circles point and lines point?

Sorry Im a noob and learning Houdini

Thanks!

-Jeremy

[edward]

Look into the Sweep SOP and Copy SOP

[acey195]

For the creation of the lines:

I think it would be even easier using an add sop, first you want to delete the primitives of the original circles (but keep the points)

then use an add sop, set the above tab to polygons, do by group and then "skip every Nth point" and set the number to the amount of points you have in each circle 0-10 is 11 points.

There are basically many things you could use:

sweep

polypatch

polyloft

and probably even more

for the placement of the objects you probably want to use a copy sop,

possibly along with a polyframe to set the "up" vector.

[mightcouldb1]

Here is an example

lines_example.hip

Edited April 28, 2013 by mightcouldb1

[sekops]

Thanks Guys! Houdini has again really impressed me

mightcouldb1, thats exactly what Im trying to achieve. The next step for me is to attach a grid to each point of those lines, I guess I could get a tangent of those points and work out an aim vector, so I can attach the grid to those points. THis setup kinda reminds me of a bird setup. I have to work out the VOP SOP a little bit more and study what youve done in that file. Great stuff.

acey195, Ive tried your method too, and manage to use a sweep, then a polypatch, That too gave me the same result, but without using the VOP SOP. Now I guess my question is, which method is quicker? If we're creating attributes and using VOPs, does that make it slower? In other words, which is more efficient?

Or what do you guys think, from your experience in using Houdini, would expliciting creating vectors from attributes in SOP or using polyframes to grab the normals?

-Jeremy

[acey195]

vops are really fast, but as long as you do not use expressions, the standard sops should be even faster, however unless you have >100,000 points you are probably not even going to notice the difference.

If you want to be sure which is faster you can use the performance monitor, this is basically a profiler for your procedure, that way you could compare both methods against each other.

Edited April 29, 2013 by acey195