Hello,

I'm working on a project, where I want to make particles emanate from a human shaped character, but I want the particle flow to feel as if handdrawn, i.e. with notable ‘frames’, though I still want them to flow in a fast pace (see attached video example). I can do this in Blender (where I mainly work on the project) by making the particle simulation skip 4 out of 5 frames when I cache it out, and then slow the video down significantly when editing the video later. But this method doesn't work when I want to animate the characters, because then I'd have to take all the retiming into account when doing the animations, and that'd be to big of a hassle.

So I'm thinking of a way to set this up in Houdini, so that I can import the animated characters from Blender and add the particles here instead. Using a pretty basic setup with a popsolver in a dop network, I'm thinking the most obvious way to achieve this effect would be to make the simulation really fast, and then somehow make the particles freeze for 4 frames every 5 frames, so that I get a result similar to what I made in Blender, but directly in the simulation instead of having to retime the video material later.

Is there a way to make a particle simulation behave like this? Or should I go about it another way?

Thanks in advance!

//William

You can use POP Wrangles connected to both the pre-solve and post-solve inputs of the popsolver to cause the visible particle position to update only every couple of frames for a stop-motion effect, without affecting the underlying particle simulation. Let me know if the attached hip file contains the effect you were looking for.

ziconic
You can use POP Wrangles connected to both the pre-solve and post-solve inputs of the popsolver to cause the visible particle position to update only every couple of frames for a stop-motion effect, without affecting the underlying particle simulation. Let me know if the attached hip file contains the effect you were looking for.

Yes, this is exactly what I was looking for. Thank you so much ziconic

ziconic
You can use POP Wrangles connected to both the pre-solve and post-solve inputs of the popsolver to cause the visible particle position to update only every couple of frames for a stop-motion effect, without affecting the underlying particle simulation. Let me know if the attached hip file contains the effect you were looking for.

The setup has a problem, however. For some reason the popwrangle nodes causes particle birth at o, o, o, world space (see attached picture). I believe it's caused by the @P = v@simP; line of code. Why is this??

Oops yeah that's because we should not be setting @P to @frozenP if @frozenP hasn't been set (which is true of newly added particles).

The fix is simple. In popwrangle2, add the line i@has_frozen = 1; to the end. Then, in popwrangle4, wrap the @P assignment in an if (@has_frozen) block.

Beautiful! It works. Thanks a ton for your help, I really appreciate it