Loft Curve Using Captured index values

Question

Problem: I cant find a solution to capturing the position of some index values set on some curves to correctly loft a curve over 3 other curves. I have had a lot of help from SOZAP on blender artists and the node setups used here are from him.

Breakdown:

I have a collection of 3 curves that are shape keyed and have the same amount of control points . Each curve has an index value that is captured that representsd the "peak":

That collection is then used in another GN setup where the three curves can be morphed one from another linearly like shape keys. The captured Index value of the original peaks of three shape keyed curves are captured then used to create an instance of a cube representing the location of the "peak" as the wave morphs through the different instances:

I then duplicate the GN group of the Morphing curves:

finally i want to loft a curve over the three GN curves using the "peak" locations of each GN curve for the curve loft. So I create another GN group and can loft a spline however I cannot set the location of the ponts to match the peak positions on each instance of the GN curve collection:

Here is my blend file:

Answer 1

I assume that you don't just want to connect the line shown in your example with the peaks of the curves, but that you want to create a complete loft between the curves.

In this case, since all three curves are in a collection, you can solve this as follows:

Here I first realize the objects from the collection so that they are available in their original form. Since you also wrapped the cubes in the objects beforehand, I also separate the curves from these cubes.

Then, based on the number of curves and the number of points, you can create a grid that can serve as a loft between the curves (in your case, a grid with 3x483 vertices).

Since the number of points on the grid and in the curves is now identical, you can now conveniently transfer the positions of the points from the curves to your grid using the indices.

_{(Blender 4.2.2+)}