Motion path U value and extrude subCurve result

[Steve Davy]

You'd think that within the same application a curve's 0-1 value would result in the same output from different parts of the program, but not Maya.

Using a motion path's U value to drive the max value of an extruded surface's subCurve only matches when "Parametric Length" is checked in the moPath, and "Relative" is checked in the subCurve node. Great, but for practical animation purposes you basically never want to use the motion path curve's parameterization as it results in irregular speed.

Does anyone know a way to get this to work? I have no idea how the subCurve result is being calculated... it appears that it's not linear so that even when its value matches the moPath's, it's nowhere near in the same place along the curve.

[Jason Stansbury]

Would using a null along path and applying a set driven key to normalize or fit the range work?

Jason Stansbury

jasonstansbury.com

c713.291.5572

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[stephenkmann]

do you have an example file? 

 I just tried a couple things , and  it sticks pretty perfectly for me.

One thing I tried that seemed to make it work , is rebuilding the curve using  0 -1 parameter range 

be sure to keep "cvs" checked on . so the curve keeps its exact same shape ( if that's important to you ) 

you may also want to look into using "curve warp"  if that works with the way you want your geometry to grow and flow along the curve

hth

-=s

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[Steve Davy]

I sent a simplified attached test scene, looks like it didn't go through.

But, a bit more testing showed that if the curve is freshly re-parameterized to 0-1 then it will work. If you move any of the CVs/change the curve length, it will not.

So, seems like it's related to curve length rather than parameterization.

I guess a solution might be to write an expression to divide the curve length by the number of frames it takes to travel from 0-1, though I haven't tried it (in my current situation it's easier to keyframe it). But since this is effectively what a motion path node does with "Use parameterization" turned off, it still doesn't make sense that simply plugging that to the subCurve max value doesn't yield that exact result.

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From: maya...@googlegroups.com <maya...@googlegroups.com> on behalf of stephenkmann <stephe...@gmail.com>
Sent: Monday, December 9, 2024 7:36 AM
To: maya...@googlegroups.com <maya...@googlegroups.com>
Subject: Re: [maya_he3d] Motion path U value and extrude subCurve result

 

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