Help Looking for suggestions on a physical-feeling rope extension

[trentthebaker]

Hello, I'm revisiting a problem that I ran into a while ago but wasn't able to figure out. I had made an old thread previously.

In short, I'm hoping to use ObiRope to make a rope that reliably extends based on force applied. I've seen in a few threads the recommended approach is to find the "strain" by comparing rope.CalculateLength and rope.restLength, but I find the result of this calculation doesn't cleanly translate to force on the end of a rope in a lot of cases. I am hoping to find something that feels like a magician pulling scarves out of their sleeve- maybe a cursor can't achieve the feel I'm going for?

I'd appreciate any tips!

Trent

[josemendez]

Hi!

The approach outlined in that thread is the correct one. Stress forces applied on the rope (such as pulling the rope) create strain (deformation) on the rope, so by measuring strain you're effectively measuring the pulling force acting on the entire rope (modulo material properties such as compliance, that modify the rope's stress/strain curve) which is exactly what you want to do.

For things like fishing rods for example, the thing most people overlook is that the mass of lure weight is *much* larger than the mass of the fishing line, so it can pull and reel it out effortlessly when casting the rod. If you keep the rope's default mass, the rope will be many times heavier than the typical lure weight so it will feel like fishing with a chain.

kind regards,

[trentthebaker]

Hi!

The approach outlined in that thread is the correct one. Stress forces applied on the rope (such as pulling the rope) create strain (deformation) on the rope, so by measuring strain you're effectively measuring the pulling force acting on the entire rope (modulo material properties such as compliance, that modify the rope's stress/strain curve) which is exactly what you want to do.

For things like fishing rods for example, the thing most people overlook is that the mass of lure weight is *much* larger than the mass of the fishing line, so it can pull and reel it out effortlessly when casting the rod. If you keep the rope's default mass, the rope will be many times heavier than the typical lure weight so it will feel like fishing with a chain.

kind regards,

Hello, thank you for the reply!

The edge case that I've seen for this approach is that if the middle of the rope gets jostled by a rigidbody, then that localized deformation contributes to an error in the overall length, which I have to assume is a force on the end of the rope, even if the rope is relaxed. Right now I'm experimenting with measuring just the distance between the first and second particles on the rope, measuring expected vs. actual, and placing the cursor slightly behind it, and it's looking a little more promising. The math to figure out exactly how much line should be let out to compensate seems a bit complex, but not impossible. I'll keep trying!

Thanks,
Trent

[trentthebaker]

While I'm running down this rabbit hole, is there a simple way to check what distance 2 neighboring particles should be from each other for a given rope blueprint? Otherwise I will try to calculate it from the radius and resolution