Hi Edmondo!

Good question. The Evaluate Length component is usually used to evaluate a curve at a specific point using a length in meters.

Don't forget to turn the N-input to False. So let's say you want to get a point 5 meters from the start of the curves you use this component.

The Evaluate Curve, however, evaluates a curve at a parameter t. And t is a numeric value that has to lie within the parametric domain of a curve.

Now the domain of a curve and the length of a curve are two different things. It's quite technical but here are some links for you to read up more into it:

https://aws1.discourse-cdn.com/mcneel/original/3X/f/1/f1e548eb7d4f09331d98bbeb351ce453a7f74aa0.png

https://www.grasshopper3d.com/forum/topics/evaluate-curve-at-t?commentId=2985220%3AComment%3A793232

I think the most important difference for me in usage is that I use the evaluate curve in cases where you got a t-value from another component and you want to use it to get a 3d point or the Tangent Vector etc. That's how curves behave with this t-value.

When I want to get a point with a specic length from the start I use the Evaluate Length. Mind you that the L-input is translated to a t-value to get the 3dPoint and the Tangent Vector, it's how curves (and surfaces) for that matter behave. I hope it's a bit more clear

Best,

Arie