Particles which only have a velocity but no acceleration don't collide properly about godot HOT 3 CLOSED

The root of this issue is the same as #87221

We currently have a part of the particle shader that removes the velocity of the particle if the length of the velocity is less than 3 and it collides with a surface. #87320 removes that section of code which will fix this issue as a result

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Here is another example. Note how the particles collide with the box when I use radial acceleration, but go right through the box when I use radial velocity.

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I believe some of this is normal behavior - In the first example, the velocity emitter had Gravity set to 0, and a negative initial velocity: So when a particle collides with the box, it gets deflected - but there's no continuous force pushing it down the sides. Enabling gravity allows it to slide down the sides of the box as usual. EDIT: I see it should be deflected, but instead stops completely. Definitely a bug in the particle physics logic.

In the second example, it seems to be caused by setting a positive animated velocity - as the particle reaches the box, the collision should impart a 'reverse force' and prevent it from going through (and should set velocity to 0ish), but the animated minimum velocity forces the particle to keep moving through the box. Animating directional velocity using the directional velocity curve also causes this issue.

I think for good collisions you need to be using the "velocity limit" curve to allow the particles to be stopped by collisions while still limiting its maximum velocity.

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