Underwater rope

[ibbybn]

Hey, I'm using obirope to tether a spear to a harpoon which you can reel back after shooting it.

If I'm using very low iteration/substep numbers the rope already looks like it's underwater but becomes way too stretchy.

If I use higher numbers the simulation is too fast to look realistic underwater.

Is there a way to get this slow motion underwater look without sacrificing stiffness of the rope?
Is this something I might be able to do with the new release or is it already doable?

[josemendez]

Hey, I'm using obirope to tether a spear to a harpoon which you can reel back after shooting it.

If I'm using very low iteration/substep numbers the rope already looks like it's underwater but becomes way too stretchy.

If I use higher numbers the simulation is too fast to look realistic underwater.

Is there a way to get this slow motion underwater look without sacrificing stiffness of the rope?
Is this something I might be able to do with the new release or is it already doable?

Increase the damping parameter on the ObiSolver. This has the effect of making the environment around the rope(s) a lot denser, making it lose kinetic energy faster (which is what happens underwater). The parameter is defined as the % of kinetic energy lost per second. So, the higher the parameter, the "thicker" the water around the rope, so to speak.

[ibbybn]

Increase the damping parameter on the ObiSolver. This has the effect of making the environment around the rope(s) a lot denser, making it lose kinetic energy faster (which is what happens underwater). The parameter is defined as the % of kinetic energy lost per second. So, the higher the parameter, the "thicker" the water around the rope, so to speak.

Very high values indeed get me there but I don't want any of the rope particles to completely stop moving. Especially if other parts of the rope are still moving this looks unrealistic. I guess I'll have to exclude all the particles under a certain velocity from the dampening?

[josemendez]

Very high values indeed get me there but I don't want any of the rope particles to completely stop moving. Especially if other parts of the rope are still moving this looks unrealistic. I guess I'll have to exclude all the particles under a certain velocity from the dampening?

Nope, as the velocity itself is part of the calculation for kinematic energy, that would require using per-particle dampening values which isn't supported.

However you can use Oni.AddParticleExternalForces to add some random disturbance to each particle, if that's what you're after.

[ibbybn]

Nope, as the velocity itself is part of the calculation for kinematic energy, that would require using per-particle dampening values which isn't supported.

However you can use Oni.AddParticleExternalForces to add some random disturbance to each particle, if that's what you're after.

Thx for getting me on the right way!
Seems instead of faking the looks I should think more about the forces involved in real life when it comes to Obi. Got something realistic looking with aambient forces and lowering sleep threshold even more.

[josemendez]

Thx for getting me on the right way!
Seems instead of faking the looks I should think more about the forces involved in real life when it comes to Obi. Got something realistic looking with aambient forces and lowering sleep threshold even more.

Remember that for very faint movements to be visible, sleep threshold should be very close to zero, or even zero.

Keep damping relatively high (around 0.4-0.7), no gravity, and things should look relatively realistic