H19 to H21 - VEX change?

[MaxMcGookin]

Hey, hopefully someone can help me or give me some advice for an issue I am having while following a tutorial. 

While following they use this script in a point wrangle.

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float rand = rand(@copynum);
float weight = chramp('curveu', f@curveu + rand + (@Time * fit01(rand, .1, 1) * chf('speed'))%1);

@anim = weight;

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However when I recreated this my version was very different (see attached screenshot). But when I tried the exact same script in H19 and it works perfectly (I included a screenshot for this too).

 

Does anyone know what has changed between these versions to cause this effect? Or have any advice on how I could recreate it in Houdini 21?

(I had a similar problem before with @Alpha not working and @alpha working instead, could it be a simple change like that? I've tried several changes like that to no avail)

RBL_WEEK08_Cloud_01.hip

Edited June 18 by MaxMcGookin

[animatrix]

This is caused by a change in chramp() behavior.

Older Houdini versions allowed chramp() to cycle/repeat when the input value went outside the 0 to 1 range. Around Houdini 19.5, this changed, and chramp() now clamps out-of-range values instead.

In your expression, the % 1 is only applied to the animated time part:

( @Time * fit01 ( rand, .1, 1 ) * chf ( "speed" ) ) % 1

But f@curveu + rand is still added outside that modulo, so the final value passed into chramp() can still go above 1. In older Houdini this worked because chramp() repeated. In newer Houdini it clamps, so the result changes.

Wrap the entire ramp lookup value before passing it to chramp():

float r = rand ( @copynum );
float u = f@curveu + r + @Time * fit01 ( r, .1, 1 ) * chf ( "speed" );

float weight = chramp ( "curveu", u % 1.0 );

@anim = weight;

That should match the old Houdini behavior.
 

[MaxMcGookin]

Amazing thank you so much for the help!

I have it working now the way it should, much appreciated. 

Cheers
Max