Currently all instanced splines are have the same diameter. But my goal is to have ability to set diameter by the first spline diameter/length. I.e. spline 1 should have diameter = 10, but spline 2 should have diameter = 0.1.
So basically each instanced lines should have lower and lower diameter based on how closer they to the tip of the first main spline.
The Spline parameter node / Factor will give you a value going from 0 to 1 along the curve,
You can use that to set the branches size.
That Attribute you need either to capture it , or store it at the beginning .
Then you need to use a realize instance so each branch can have a different radius,
And then use the attribute you stored earlier, maybe through a map range node to make different radius size
A simple tutorial either for a tree, or for a lightning should explain every details !
Yeah without the realize instance the change apply to the instance like if there is only one.
So changing the radius will have an effect . This behavior is powerful since if you have 100 000 instances the operation like subdivide is computed only once.
But most of the time we want variations