Next up is the loop unedited on the left, and on the right are the new particles from frames 20 – 44 that I’m merging in from frame 66 onward:Īnd now, the unedited loop next to the previous red, green and blue particles combined:Īnd finally, just the result of the looping by itself without the point colours: To illustrate, this gif shows the unedited loop on the left, and next to it on the right is the loop with no new particles spawned after frame 66 (particles go red on 66):

This guarantees that all the particles that are alive on frame 89 match exactly with frame 44. From frames 66 to 90, copying in all the particles that spawn between frame 20 –> 44.Deleting any particles that are spawning after frame 66 (i.e, making sure all particles have died before frame 90).The technique I’m going to use to improve the looping is somewhat like a crossfade.įor this loop from 44 –> 90, I’m modifying the particles in two ways: This makes a loop that is 46 frames long, here it is with no blending: The last frame needs to be after frame 68, so I’m choosing 90. Going back to my rules, with particles that live 24 frames I must choose a first frame >= 24 (for this example, I’ll choose 44). The simulation is 400 frames long (not all shown here), but that ended up being overkill, I could have got away with a much shorter sim. The fluid sim I’m using is some lumpy fluid going into a bowl: I have some ideas about how to get rid of these requirements, but not sure if I’ll get back to that any time soon.įor the example in this post, I am keeping particle lifetime pretty low (0.8 to 1.0 seconds, using a attribute on the source particles, so a 24 frame loop). The last frame of the loop must be >= the first frame number + the particle lifetime.The first chosen frame of the simulation must have a lead up number of frames >= the particle lifetime.There are a few conditions that make my approach work: I won’t go into the fluid sim setup, it doesn’t really matter too much what it is. So begins the looping particle journey… Technique overview I don’t really do much VFX related work at the best of times, something I need to do more of in the future 🙂Īnyway, I was recently chatting with Martin Kepplinger, who is working on Clans Of Reign, and he was looking to do a similar thing! For a while I’d been planning to look into making looping particle systems in Houdini, but hadn’t found a good excuse to jump in.

Houdini 16.5 no promote parameter