Help Raising stickiness in collision material makes particles spastic but not sticky

[josemendez]

The fluid just runs straight off though as you can see in the video, not a single particle sticks or shows any signs of friction.

Is the knife a kinematic rigidbody once you pick it up?

Friction and stickiness are forces. For them to have any effect, the objects they're interacting with (in this case, the knife) need to honor forces properly. To understand this, try placing a cube on top of a floor in Unity and give them a physics material with full friction. Then, move the floor around: the cube on top will simply slide as if the floor was made of ice, because as far as the physics engine goes you're not actually "moving" the floor: you're teleporting it around. For friction to kick in you'd need to apply the floor a force/acceleration to increase its velocity, then the box would also increase its velocity as a result on frictional contact between them.

Another possible cause would be the mass of the knife vs the mass of the fluid, check that the mass of the particles (should appear in an info box in the fluid blueprint inspector) is smaller than that of the knife.

And is there something that can be done about the jittering when using stickiness? Even lower values like 0.2 cause it. Is this the same problem that forces you to lower the simulation timestep for high viscosities or something else?

There should be no jittering when using stickiness... my guess is the mass ratio between the fluid and the knife is very large. See the included "Fluid Viscosity" sample scene for reference.