Suggestion / Idea How to Achieve Realistic Specular Reflection in PBD Particle Collisions?

[josemendez]

I believe I can use the MaxDepenetration value and reduce the collision iteration count to approximate the rebound effect.

You can't. Restitution depends on the particle's velocity (a fast moving particle will bounce a lot more than a slow moving one, since it has more energy), while max depenetration does not: it just sets a maximum velocity for particles moving out of a collider.

When particles are born inside the collider, the MaxDepenetration value can effectively limit the speed at which particles leave the collider. But when particles are born outside the collider and move towards it, a lower MaxDepenetration value seems to cause the particles to rebound quickly and violently. Why is that?

If particle CCD is set to 0, particles will be allowed to penetrate the collider when moving towards it (otherwise their approach velocity would be modified to prevent them from penetrating the collider in the first place).

Since a small max depenetration value does not allow their velocity to change sufficiently fast to resolve penetration in a single simulation step, they "sink" into the collider and are launched out of it over multiple steps. This is what causes the "bouncing" effect.

Why does this behavior not align with the former case and the phenomenon described in the user documentation where cloth bounces off the ground?

It does, the cloth in the documentation starts inside the floor and is projected out of it at the speed specified by max depenetration.

kind regards,