lisux Posted October 20, 2011 Share Posted October 20, 2011 This is really cool eetu. I love this fractals. Quote Link to comment Share on other sites More sharing options...
KHERMAH Posted January 4, 2012 Share Posted January 4, 2012 After a whole year of missing in action, came back here and all I can say is WOW!! Drooolling. Thanx EETU Quote Link to comment Share on other sites More sharing options...
eetu Posted February 8, 2012 Author Share Posted February 8, 2012 (edited) Q: What does a TD do when he has some free time? A: Stupid shit. I saw the emNewton N-body particle video and began thinking whether it could be sped up with a FLIPish approach. Looks like it can grav_05.mov I'm doing it as follows: 1. Accumulate all masses to a volume, that is, add up all particles within a voxel. 2. Create another (vector) volume, and for each voxel, calculate the gravitational force exerted on it by the other mass voxels, considering them as a point in the center of each voxel, with the accumulated mass thereof. Add all these forces together. 3. For each particle, read an interpolated value from the volume with the gravitational forces, use it as acceleration. 4. Repeat. Steps 1 and 2 are done in a SOP Solver, step 3 in a POP Solver, both in the same DOPnet. This way it will work with any other forces as well. Example of mass and force volumes: The advantage of doing it this way is that you can stuff a shitload of particles through it. The naive particle-to-particle force calculation is of N^2 complexity with regards to particle count, this method is of N^6 complexity with regards to linear voxel resolution. I've done some 10 million particle sims and it didn't slow things down too much, but for emNewton going from 1 million (the highest in their video) to 10 million should slow them down 100-fold. The volume sizes I've used this far have been 30-60^3 - doesn't sound like much, but seems to be ok. The flipside (ha) of this method is that the result is somewhat incorrect The gravitational forces are greatest when the particles are next to each other, but in my version the particles within the same voxel do not affect each other. The result is a more tame version of the simulation. I should try and do the naive particle-to-particle approach too, would be interesting to compare. I do not have pretty renders like the emNewton stuff, but here are a few test quicktimes: grav_01.mov grav_02.mov grav_03.mov grav_04.mov Edited November 29, 2020 by eetu Quote Link to comment Share on other sites More sharing options...
magneto Posted February 8, 2012 Share Posted February 8, 2012 (edited) Hey Eetu, when you said "I've done some 10 million particle sims and it didn't slow things down too much", are you talking about the viewport performance? I liked how that guy had interactive feedback in the viewport. But your stuff must be better Edited February 8, 2012 by magneto Quote Link to comment Share on other sites More sharing options...
eetu Posted February 8, 2012 Author Share Posted February 8, 2012 Hey Eetu, when you said "I've done some 10 million particle sims and it didn't slow things down too much", are you talking about the viewport performance? I liked how that guy had interactive feedback in the viewport. But your stuff must be better Ohh, I didn't even watch the viewport video. This system is far from interactive. With "not too much" I meant going from 1 to 10 million doubled the sim time, as opposed to the 100 times I'd expect from their system. I think it was something like from 20 to 40 seconds per frame, with a small volume size. I think their rendered video said 10 sec sim time for 1 million particles, so 100x that would be 17 minutes per frame. They do quote only a 10-fold increase from 100k to 1 million, so maybe they are not using the brute force method. The only way this system is better, is that it will work in the "dozens of millions of particles" -range, while theirs will take forever. Unless their system uses some clever hierarchical acceleration scheme (barnes-hut or somesuch), in which case it is better in all respects Although it's nice that this is all VOPs, no code. 1 Quote Link to comment Share on other sites More sharing options...
magneto Posted February 8, 2012 Share Posted February 8, 2012 Still way awesome though man, that in no time you did what those guys do with a specially coded compound Btw same guy also has this: done using emFluid4, his flagship compound. Quote Link to comment Share on other sites More sharing options...
eetu Posted February 8, 2012 Author Share Posted February 8, 2012 Btw same guy also has this: Oy, that's wonderful, that needs to be plagiarized post haste! 3 Quote Link to comment Share on other sites More sharing options...
magneto Posted February 8, 2012 Share Posted February 8, 2012 Can it really be done in Houdini? Quote Link to comment Share on other sites More sharing options...
Solitude Posted February 9, 2012 Share Posted February 9, 2012 Can it really be done in Houdini? Totally. Shouldn't be too hard either... Smoke sim -> advect points -> color, scale, rotation based on velocity -> copy boxes to points (or instance). Done. --Ian 1 Quote Link to comment Share on other sites More sharing options...
magneto Posted February 9, 2012 Share Posted February 9, 2012 Totally. Shouldn't be too hard either... Smoke sim -> advect points -> color, scale, rotation based on velocity -> copy boxes to points (or instance). Done. --Ian Awesome man, I love the power of Houdini Quote Link to comment Share on other sites More sharing options...
Solitude Posted February 9, 2012 Share Posted February 9, 2012 Awesome man, I love the power of Houdini Me too! I'll give it a shot when I get home tonight I think. Quote Link to comment Share on other sites More sharing options...
magneto Posted February 9, 2012 Share Posted February 9, 2012 Me too! I'll give it a shot when I get home tonight I think. Thanks man, I don't know about smoke sims yet but my only concern is would the boxes not have to be high-res enough in length/height to deform like that in the vid, which didn't look segmented but smooth? Quote Link to comment Share on other sites More sharing options...
Solitude Posted February 9, 2012 Share Posted February 9, 2012 (edited) Thanks man, I don't know about smoke sims yet but my only concern is would the boxes not have to be high-res enough in length/height to deform like that in the vid, which didn't look segmented but smooth? I don't think the boxes themselves are actually deforming outside of scaling along the direction that they are moving... 99% sure it's just an optical illusion since there are so many overlapping boxes. Edit -- that'd still be possible -- however much more computationally complex. Edited February 9, 2012 by Solitude Quote Link to comment Share on other sites More sharing options...
magneto Posted February 9, 2012 Share Posted February 9, 2012 I hear you, I sort of noticed that illusion when I watched it again Still would be good to put emFluid4 to shame with some Houdini magic Quote Link to comment Share on other sites More sharing options...
Solitude Posted February 9, 2012 Share Posted February 9, 2012 I hear you, I sort of noticed that illusion when I watched it again Still would be good to put emFluid4 to shame with some Houdini magic ....annnndd Done. Cubes: http://fx-td.com/content/misc/Pyro_Cubes.mov Not perfect, but certainly a good start in the right direction. Wires: http://fx-td.com/content/misc/Pyro_Wire.mov I keep forgetting about polywire... sooo bendy 'cubes' is actually quite easy in this case, just a little slower to generate the geo. I lowered the particle count a lot so I didn't have to wait too long. Also note: the normals are smoothed so they look rounder than they actually are. Also, the artifacting at the beginnning -- I think you should only have to add a radius attribute to clean that up... can also drive that by speed as well if you wanted. Hip file: http://fx-td.com/content/misc/Pyro_Cubes.hip Enjoy! P.S. -- Sorry Eetu for hijacking the thread! Just looked like too much fun to pass up. I'll move it elsewhere..earlier next time. 3 Quote Link to comment Share on other sites More sharing options...
magneto Posted February 9, 2012 Share Posted February 9, 2012 Dude, that's awesome. Well done Also thanks for the scene, will be good to study. Quote Link to comment Share on other sites More sharing options...
rdg Posted February 9, 2012 Share Posted February 9, 2012 I really hate to hijack this thread - but: Bring it on, Eetu! Quote Link to comment Share on other sites More sharing options...
Magnus Pettersson Posted February 14, 2012 Share Posted February 14, 2012 (edited) I hear you, I sort of noticed that illusion when I watched it again Still would be good to put emFluid4 to shame with some Houdini magic Another hijacking of eetus lab, he will need to bring out the shotgun soon to clean up his lab .. Decided to actually make a render this time: .. houdini boxes for the win Edited February 14, 2012 by Magnus Pettersson 3 Quote Link to comment Share on other sites More sharing options...
magneto Posted February 17, 2012 Share Posted February 17, 2012 You pulled out that effect pretty well, and made it even better that the ICE vid Quote Link to comment Share on other sites More sharing options...
Sifis Posted February 17, 2012 Share Posted February 17, 2012 You pulled out that effect pretty well, and made it even better that the ICE vid Yeah, much more visually interesting than the ICE videos, Awesome! 1 Quote Link to comment Share on other sites More sharing options...
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