Position of a point on curve

[kmagill]

Hello all,

I have a curve in the XY plane. Is it possible to retrieve the Y value of a point in the curve given an X value?

Thanks.
K.

[joojaa]

yes...

what do you need to do? interactive or querry just once?

[kmagill]

What I'm trying to do is to have a row of 'Posts' (cylinders) at fixed intervals, and to have their height set by a curve running over them.
The curve's CV points can be moved and the Post's height needs to adjust automatically. I think this can be done in an expression attached to each Post, but the problem I

[alexnowotny]

If you use a curve with one cv-point over every cylinder you get the desired height-value with:

getAttr curve1.cv[0].yValue

[kmagill]

Alas I would do that, but the curve can only be described by exactly 4 points, which are not necessarily above any of the cylinders.
So back to my problem, given the X value of a point on a curve in the XY plane, how do you retrieve the Y value?

Thanks again.
k.

[campbell]

how about using Animated Snapshot for the posts animated along the crv w a motion path?

otherwise, id go about it the agricultural way: have a straight curve, w a single x value and a length longer or equal to the y range your measuring, you then intersect this curve w the 'placement curve', moving it along x whilst you read off y from the intersection locator's world position attrib.

[kmagill]

I didnt think it was possible to do in intersection test between 2 curves.. only between surfaces.

Anways. I've found a solution, by rearranging the problem. So thanks for everyone

[joojaa]

you can intersect two curves. with the trim command if i remeber correctly

[someboy]

use the closestpoint on curve node.
You will have to compile it.
It will supply you with all the info you need and more.

[campbell]

by its very nature, that wouldnt work (if you scrub in flat y), as the point will jump (imagine a peak, where itd creep up one side, then jump to the other, missing the summit). i dont see what the issue with using vanilla curve intersect is? especially since its stated the curve is in a plane. if you want normal and tangential info, just plug the interesect locator's local posX value into a pointOnCurve node.

whats this insteresting stuff about using trim joojaa?