QuickDini [rope]

A ropey Monday

Earlier today, someone on Discord asked for help creating a multi-strand rope in Houdini. Good question - how do ropes actually work?

Braiding + recursion with alternating twist direction? I’ve got you covered!

Sweep it up

The Sweep node already gets us halfway there. Set it to a columns surface, add twist, and we’re almost there.

All we need is a few more iterations of this and we could just serialize Sweep nodes all the way down but that’s no fun. How about we stick it in a loop, and setup all the parameters as detail attributes using a Multiparm Block?

Setting up a Multiparm in a wrangle is easy. Add a folder, set its type as the block, then add any parameters you want in the folder. You can then reference its of these parameters using their name + the iteration index (starting at 1).

Next we setup the detail attributes, making 3 arrays for the columns amount, the radius and twist of each iteration. We’ll also fetch the parameter count to use as the loop iterations:

vex

int count = chi("props");
int cols[];
float radius[];
int twist[];
for (int i = 0; i < count; i++) {
    cols[i] = chi("cols" + itoa(i + 1));
    radius[i] = ch("radius" + itoa(i + 1));
    twist[i] = chi("twist" + itoa(i + 1)) * 360;
}
i[]@cols = cols;
f[]@radius = radius;
i[]@twist = twist;

Then setup the loop and use the iteration index to fetch our attributes:

And now we can control the whole thing from the wrangle:

Going any deeper than that starts costing a lot in performance, so we can just instead do some displacement. Here’s a simple VOP setup in COPs:

Fuzz-Buzz

Bonus round: Scatter points on the surface, copy curves onto them:

And there you have it, quick & dirty rope! Go wild, take it much further