Doing the same steps with the bi-tangent is correct, normals that spike out from the circle. I tried the tangent and cheated by forcing its name to be N, thus making it become the normal instead. Ok, there's always other options in Houdini.Ī facet sop with 'post compute normals' enabled will makes valid normals on the circle, but they're all set to which we don't want. Looks like the normal sop doesn't work well with curves. Look at the geometry spreadsheet, you can see is being created, but all 3 components are 0. A normal sop in point mode seems like the most obvious choice, appended immediately after the circle: Time to add some attributes! If we create an N attribute (Houdini's standard name for a normal), the copy sop will orient the boxes along the normal. None of those attributes exist on the circle. The reason for this strange behaviour is simple the copy sop looks for certain point attributes to orient the copies. The boxes are doing interesting rotations, but its not controllable, and not the effect we're after. Here's what happens with just a circle that's rotated, then has boxes copied onto it:

The setup was easy enough, which lead to the first major problem controlling rotation of the copied boxes. I figured I'd start the basic setup first, then concentrate on the other 2 points later. Start with one box per circle, and grow them smoothly so that they're all in place when the rotation is resolved.Start in a random state, and finish aligned.But 2 extra things required a little more thought: another copy sop to put the boxes on the circlesĮasy enough.take a circle, copy sop to make several copies.When I saw Gary's video, I broke it down into a few steps: Here's my solution to Gary's initial question: 7 Resample sop to generate evenly spaced boxes.3 Start with random rotation and finished aligned.

Houdini vex rotate