Create Velocity on "stick to location" Particles

[sant0s]

Hey all

If I emit particles on an object that has animations (shape animation for example) and these particle stick to emit location, the particles do not have velocity.
when I export the particles with alembic, alembic of course do not recognize any velocity.

is there a way, to create a second point cloud that follows the original particles so that they have particles? something like goal...
maybe there is a smarter way to create velocity?

thank you!
sant0s

[Tekano]

you could use 'inherit emit velocity' node after emission but stick to velocity ignores any velocity anyway

also you can compute your own velocity from current frame position and previous frame position and add it back on for the needded alembic attribute

[sant0s]

hey Tekano,
thx!

could you point in the right direction, how to compute the velocity between frame positions?

I actually do have another solution for my setup now, but always interested in how to do stuff like that.

[Pooby]

It's a simple subtraction one from the other

[sant0s]

dont understand it, I am from waldorf school.. always need to have colors and so
but no prob, just doing it another way.

edit: okay, I found the "previous frame" node.
but where do I have to plug that now?
and do I have to divide it by current frame or something to get a middle value?

[Tekano]

thats it you got it good. that is essentially what the velocity vector is - the difference in direction and magnitude (length) from one frame to the next for sure you can increase it or add whatever it with multiply by scalar and you can pass this vector down alembic as an attribute or rewrite the point velocity one , or which ever one is stored or asked for motion blur depending on renderer and what geometry type it is you intend to render

[sant0s]

ohhh... thats "easy"
motion blur is working , hehhe.
thank you very much guys.