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Everything posted by Farmfield

  1. Bullet and scale

    Yes, in the Cg Society destruction course, I think Pawel Grochola says 2x the scale for most sims, even doing something like a smaller building, if you have a lot of detail, at least. And it seems to work similarly in the other direction, you get to a point where too large simulations might start to behave weirdly and you need to scale them down. In both cases, you might have to compensate, tweaking the timescale, to get it looking correct for it's intended scale. That being said, I might be completely wrong and/or someone of the really smart people here will come in and explain it better.
  2. Grain Solver - Animated Geometry - Sandman

    ...but yeah, it's an amazing place. The most positive AND negative about OD Force, though, there's so many brilliant people roaming this place, it's easy to feel really dumb.
  3. Grain Solver - Animated Geometry - Sandman

    Now it's like 20 past midnight, stop pestering me, you "#¤%&/()
  4. Grain Solver - Animated Geometry - Sandman

    Ah, I just thought you wanted the surface emit. If you want to keep the grains contained within an animated shape, I would set it up using a volume gradient to keep the particles at a specific depth in the mesh. It's 15 minutes past midnight here, though, so I won't be setting up a demo for that right now. I'll see if I get the time tomorrow.
  5. Grain Solver - Animated Geometry - Sandman

    So grains is based on POPs thus you can set it to emit like any POP setup.:) sand_emit.hiplc
  6. One simulation 2 densities

    Looking at it now, I was actually wrong in what I answered you on Vimeo - I confused Mantra and Arnold's volume shaders. Now, you could build a (or modify the Pyro-) shader to do what I said, split up the fields in one shader, but you can't add fields in the shader GUI, you gotta do it in SHOPs. But it's also redundant as I at least thought you had two different volume objects in DOPs - with one object there's no way to split it up "after the fact".
  7. Cloth collision

    The good thing with grains is they are particles, so they are not only fast, you can also plug in POP forces directly into the solver - and there are a lot of great POP nodes. Well, check it out, if it works, it works - this is all trial and error.
  8. Cloth collision

    It all depends on what you need to do and what works. Grains (crap name, Position Based Dynamics is better) are like any other solver, great for a lot of stuff, less great for others.
  9. Cloth collision

    Kinda depending on what you wanna do, but check the grain sheets for cloth - they work when they work - but are tricky to tweak to look different than they look. This is an old, old setup and sadly I couldn't find the scene file, but it's pretty straight forward, grain sheets and POP forces in DOPs.
  10. So I had this idea for a very simplified setup for this kinda thing (link) but I ran into an issue very similar to what we solved for the "perfect tetrahedral tessellation". The idea is to create a per primitive "box" and then (in a foreach) copy and reshape the object box to each primitive box, then use the new point positions to shift the copy object into place with a lattice. I tried to use the extract transform setup we used in the tetrahedron reshaping setup, but no luck. My brow is just to low to solve this it seems. And yeah, it's kinda tricky to explain, hehe, but if you're wondering what the h*ll I'm drivelling on about, here's the setup. per.prim.lattice.v1.hiplc
  11. Oh yes, now we are talking. Though you still some VEX cleverness I need to dig into, you do a lot of stuff here in line with my original idea. This both answers the question as well as shows off some great workflows I know I'll have use for. An example being the wrangle SOP creating a point in the middle of a primitive (which I knew) also adding the normal from that prim (something I tried to solve in VEX for quite a while before giving up, creating my 6 node setup to do just that, hehe ). So yeah, great work and much appreciated, Petz.
  12. fluid driving rbd/bullet?

    Packed prims are particles, so you can use POP forces directly into the Rigid Body Solver as it has a multi solver inside. rbd_advect.hiplc
  13. LOL, yes, but you forego the whole point of doing this without being extremely clever with VEX. So even if you just posted one of the cooler setups I've seen in VEX, kinda solving the end goal of the setup, it doesn't answer the question. That being said, with this setup you basically did a knit setup with 1/25 the amount of nodes compared to the one that was posted here a couple of weeks ago. per.prim.copy.petz.hiplc
  14. How to perfect fractured a sphere into tetrahedrons ?

    So I just painted myself into a similar corner, trying something similar, reshaping one box to another - and got as stuck as I did with this. I created a thread about it here, if anyone wanna take a look at it.
  15. Disregarding the complete control you have in Houdini, or rather the methodology that enables that control, the workflow in Thinking Particles is truly brilliant. In TP I exactly know how and in what order the data is handled, in Houdini DOP's, after 1-1/2 years I still don't understand completely how the data flows through the network, the order of calculation, so to speak - and it messes with my mind sometimes. Well, at some point I'll get it, hopefully. And I use the shelf stuff extremely sparsely and if I do - for creating setups - it's mostly to see how the SESI guy's set it up. My default approach is to come up with a solution, set it up and see if it works and if it does it now becomes about simplifying it as much as humanly possible, then start tweaking it. And if I need to set something up, if I know how, before using the way I know I try to come up with another way to do it. Because Houdini. For me this is like playing with Lego's, the fun isn't in building stuff from blueprints, it's just playing with that huge pile in front of you and see where it leads.
  16. To your defence, it's really not as simple to control spawning in TP or Pflow compared to Houdini - though there's a lot that is simpler in TP and Pflow than in Houdini POPs too, hehe... 1-1/2 years ago when I started out in Houdini, one of the first things I tried to set up was to rotate a particle around it's axis of travel (and I mean inside POPs, not after) - something I finally learned how to do like a month ago. But back to this subject of the thread... Constraints in Houdini can be really tricky to get it looking/acting like you want it too. For setups where you want clustering and that kinda sticky, flexible breaking, I believe a combo between glue and cone twist constraints are a good solution. The problem with cone twist constraints, though, is they haven't a breaking strength, so you gotta do a lookup on the constraint force and manually setup a dissolve/delete of those constraints in a SOP solver. That makes it really controllable, but it's not the most efficient in regard to tweaking the settings, but it is what it is, you gotta work around it. And I have yet to find a good, reliable way to setup a split constraint system for clustering, that is using a higher strength to cluster pieces and lower strength between them. Though the problem seems to be more in the constraints solver than in setting it up, because even if I create a setup like that, it's really hard to get it to behave like I want it too - but then again, perhaps I'm missing something. Another solution would be splitting clustered pieces in a SOP solver based on some rule. The clustering is done using the name attribute, so if you were to take a cluster and give it's pieces separate names, it'll be handles like separate pieces by the Bullet solver. Something I have yet to try is doing do secondary fracturing in a SOP solver... Think how you'd set it up in TP, a rule shuffles a particle into a group, then you use volume breaker to fracture them, it's just an awesome way to do recursive fracturing. And you could set it up similarly in Houdini. The idea is, you do the initial fracturing in SOPs, feeding that into the sim. Then you setup a threshold in a SOP solver where a set hit value for a piece will unpack it and run a voronoi fracturing, repack the pieces and feed them back into the simulation. It should work for doing recursive fracturing. You could even set up a constraint network for the new pieces.
  17. It's a lot of fun simplifying stuff, but it's also about simplifying stuff because it's easier to tweak, faster to tweak, and quality is always in the tweaking. I see a lot of VFX in movies where they used a lot of complicated setups, amazing simulations, but they didn't leave themselves time to tweak it so in the end it looks like crap anyway. And this is in part on the supervisors, but also on the artists not to spin too much into details. There's a lot of value in backing away, looking at the big picture.
  18. This is probably really, really simple but I just couldn't figure out how to do it using the group SOP. I just want to group the edge points between the primitive groups. As simple as - accept not simple enough to me to figure it out. group_problem.hiplc
  19. Group edge/edge points between groups

    Hehe, like I didn't try that - looking at your setup I realize I at least was on the right way, I just wasn't clever enough to make it work. And thanks, much appreciated. Hopefully this will be easy the next time I run into something similar.
  20. I was actually kinda baffled when I came up with this technique, it's almost like, nooo, it can't be that simple - but it worked. The ray SOP moves incoming points to the surface of the surface object piped into the second input - really handy to use in a SOP solver in DOPs for keeping particles on a surface, if nothing else. Attached a quick setup as that is the simplest way to get the concept of the thing. And I don't merge back the points, the attribute transfer transfers the position attribute, so I just shift the points of the outside edge of the fractured pieces towards the displace edge. My idea was actually to do the noise and ray operation directly on the edge points of the fractured pieces, but I couldn't manage to group just the edge/edge points between the inside and outside groups, so I worked around it with splitting the stream, doing the displace and attribute transferring the positions back. Good I came to think of it, I'm actually gonna start a thread on that and get the setup simplified even more. ray_demo.hiplc
  21. A lot of very advanced setups in this thread, just what I wanted to avoid when I created this. Sometimes you just need something simple. I feel almost ashamed to post a setup like this, but someone might have use for it. simple.edge.displace.v1.hiplc
  22. This is the setup. Link to the scene file in the description as usual but I'm attaching it to this post as well as it's in line with the thread. Scene file: simple.edge.displace.v1.hiplc And here's how you set it up to sim with lowres and render highres... Scene file: simple.edge.displace.SIM.hiplc
  23. I'm posting a setup I think you'll be interested in on Vimeo in a couple of hours, a very simple, fast, very straight forward way to break up voronoi fracture edges while keeping the edge normals so you don't get any obvious cracks before breaking stuff. The techniques I've used before was so friggin involved with using VOP's to align a displacement normal with the surface, etc, so I thought there just gotta be a simple way - and this is what I came up with. It's meant to be post sim effect and as it's still all convex geometry, it'll still be fast so sim with Bullet. In the clip I'm rendering I'm fading the fractured pieces from straight edges to the displaced one, thus the animated edge in the gif.
  24. Hehe, I think it's as simple as Houdini handling the normals correctly. As I said, you can't have a polygon (primitive) without a normal, so as long as you orient them correctly, it should be done right just from creating them in the first place. That being said, when you add detail to your inside surfaces, it can be a pain getting the normals looking good, though a material with displacement usually breaks that up enough for it not to be an issue.
  25. particle "beam"

    ^ also a very good point. (though AE makes me cry, even if VCP's plugin's are pretty awesome)