Question about additive point position recursion in Vex

[noc2]

Hi;

I have come to see that one needs to use a wrangle inside a foreach loop to get an additive recursive operation. But I really need to know if I really need to do that. Let me present a scenario first:

Imagine there's a line with say, 5 points.

Using a Point Wrangle Sop, I want to:

1. Rotate the first point 0 around its neighbor, which is 1.
2. Then I want to rotate point number 1 and 0 in its just previously altered position around point number 2.
3. Then I want to rotate point 0, 1 in their just previously altered position and 2 around point 3, and so on...

My problem is that I can't get the point wrangler to retrieve the altered point positions to work on inside a for() loop. The point() function simply returns the initial positions of the points :-/ Now, I got this to work inside a foreach loop, but when the point count reaches somewhere around 100, the cooking rate drops like crazy  And for something as easy as this task, I found it overkill to use a foreach() sop inside a compiled block and such.

I would be more than grateful if someone could enlighten me on the very subject.

Many thanx in advance.

Cheers;

AJ

[tamagochy]

Look here curve unroll setups, maybe you will find answer there

[konstantin magnus]

Hi Ajlan,

you'd usually take a rig wrangle after a rig doctor:

float u = vertexcurveparam(0, i@vtxnum);
float amount = chramp('roll', u) - 0.5;
rotate(4@localtransform, amount, {1,0,0});

 

roll_curve.hip

[noc2]

Hey there @konstantin magnus;

Thank you so much for your reply. I was keeping kinefx as a backup for this task as it provides a built-in parent-child relation between points, which is great! Thank you so much for the code, highly appreciated 

I came across this mini tutorial on YT based on Geometry Nodes in Blender a while back: 

So essentially, Geo Nodes is a one big VOP in itself. Here, he makes use of the repeat zone, which is a for-each loop basically, to roll the points upward. I kind of set this one as a challenge for myself, thinking that if this is easily doable in geometry nodes in a single network, maybe I could do it in a single wrangle... It turns out that although geo nodes is able to do an additive recursion, I found that that may not be entirely the case in Houdini, hence the reason I wanted to consult on the matter in od-force.

I also checked out Matt's CGwiki page and checked out his article where he first tackles unrolling a rolled up line geometry and then gets into the reverse of the prcedure, which is the exercise I gave myself  Just wanted to see if I could get it done in a single point wrangle without having make use of a for-each sop without referring Matt's methodology directly and coming up with my own, no matter how clunky it may be

So basically, mu question is this; is it not possible to deform points and recursively deform those deformed points in Houdini?

Cheers;

AJ

[Aizatulin]

feadback_loop_rot.hipncYou can use a feedback loop for example

feadback_loop_rot.hipnc

@edit: you can do it within a wrangle aswell

feadback_loop_rotA.hipnc

Edited February 14, 2024 by Aizatulin

[noc2]

Ah, thank you so much @Aizatulin This is exactly what I was trying to accomplish. So much to study here and learn from. I truly appreciate you taking the time to do this.

Lotsa cheers;

AJ

[hannes603]

you can also use path deform node . then you dont need code for this at all

spiral_path_deform_enroll_curve_growth.hip