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sim

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About sim

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    Peon

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    Simeon
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    Australia

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  1. I know one can do just about anything in Houdini, so really my question is: can this be done in a non-'insanely difficult' way? I'd love to try and set up a walking treadmill simulation. The idea is that a character starts from standstill to a walk and then to a run. And then just for fun the treadmill inclines upwards so the character ends up running up a slope. I'm hoping to make the treadmill react to the character. It works to keep the character stationary - however the character moves. I'm thinking I might be able to make use of the crowd agent toolset. As I understand it, each individual is a particle. Perhaps the treadmill can read the forces that motivate the particle and apply an equal opposite force to keep the particle 'stationary'. (Visually represented as a treadmill.) And the other thing I was hoping to leverage from the crowd tools is the terrain adaptation. So that the character's feet would adjust to the treadmill as it inclines upwards, and also leaning the torso forward to keep the character upright. Am I on the right path here? Is there perhaps a better alternative? I'm open to any suggestions. Character animation and crowds is not a part of Houdini I've spent much time in. 'regards, Simeon
  2. Hey, I just wanted to update here and mention that I changed my collision geometry from the curved tubes you see above to extruded boxes. The box was extruded along a path much like a 'V' with a little flat section at the bottom. The end result is pretty much identical to the image above - however no curved surfaces. The sim times are much, much faster. Didn't change anything else. -Sim
  3. Hi all, I'm doing a simulation of a cloth sail being gathered up. In real life, and in the final render, it would be done with ropes that loop around the bottom of the sail and pull it together. For my testing, I'm using thick 'hooks' that pull the cloth upwards. It sims verryyy slowly. I'm sure there must be a better way. I'm open to suggestions and I've included my file if anyone would like to take a look. I feel like I ought to be considering an entirely different type of collider. A point or wire collider - if those exist? In the dopnetwork I'm bringing the hooks in as a 'staticobject' that I've also pre-converted to a volume and using as a 'proxy volume' in the Collisions - Volume tab. Most other settings I've left at their defaults. The hooks are as thick as they are because I found that thinner ones kept passing through the cloth. 'regards, Sim cloth_hook_01.hipnc
  4. improving this smoke

    Hi, here's the file. I cut out everything else that wasn't related to the smoke sim. And unfortunately the geo that feeds the sim is too large to include here. But it does show my setup and all the settings I've used. -Simeon smoke_cluster_01.hip
  5. Hi all. I've been learning much about smoke sims in the last few weeks. I have here a smoke test and I'd like to improve it. There's a number of issues going on here, but the first one I'd like to get to the bottom of is the way the smoke is popping (pops) into existence. In the clip below, the popping starts happening 3sec in, but you can particularly see it from 8secs onwards. Solid blocks of smoke appearing before they start dispersing - way too rapidly. So what's happening is that I have a large (110, 3, 60) voronoi fractured terrain that suddenly cracks all the way through the middle and then starting from the camera pieces start falling away. I'm using a 'delete' sop that's deleting geometry that isn't moving (v<0.9). So the blocks of smoke that suddenly appear are when the terrain pieces start falling fast enough to go into the smoke source. And the smoke sim is a cluster system with ten points. But it's too sudden and strong, how can I make them fade in? I'd appreciate it if anyone could give some input on this and on any of the other issues I'm seeing in this smoke test. (Other issues being the stair stepping in the close to camera smoke, and that the turbulence and dispersion? seems much too high. I'd like to slow the smoke down a lot.) 'cheers, Simeon
  6. I'm sure this is simple, but I can't figure it out. I have a destruction sim of ground falling away. I'm now adding smoke to this. For the fuel source I am deleting the geometry based on velocity, so that only moving points of the geo remain to be fuel. But now I'd like to put down a point attribute that lists the frame that a point comes into existence? I've tried using an attribVOP with an 'if' block inside. For the 'if' condition I use a 'compare' of the 'frame' attribute itself. If It's zero, then go ahead and change it, otherwise leave it alone. (Is what I think my logic is doing.) But this isn't working. I've attached here a very simple setup showing what I've tried to do. Currently it's failing and writing the current frame number to every single point. I'd appreciate any help. -Simeon startFrameAttribute_01.hip
  7. That's awesome. Thank you. I was so close, (But no cigar.) Looking at 'fractureTesting_04_post_2.hipnc' - the important things was to move the velocity transfer to after the assemble sop. And then in the rbdPackedObject to 'inherit velocity from point velocity', but turn off 'Create Active Object'. I read the description of the 'Create Active Object'. It kinda makes sense. The way I've interpret it is that when it's ticked, all the objects inheriting velocity will move on the the first solving frame before the popwrangle node can make them all inactive again? Thanks again, Simeon
  8. Hi all, when I use 'Inherit Velocities' on the rbdPackedObject in my sim, the pieces all jump (or pop) to a different position based on their velocities in the first solve frame - Frame 2. I'm trying to get better control of the exploding animation of my fractured rbd object. I came across the qlib destruction example recently and have been modifying my setup to use their method. It involves putting velocities onto the fractured object before it goes into dops. I like the controllability of this. I've spent all day trying to find a way to get those velocities on my pieces without the initial pop/jump happening. I've attached my testing file. Any help would be greatly welcomed. By me -Sim fractureTesting_04_post.hipnc
  9. Hey those are both great ideas. Pavel, I tried out your suggestion a few days ago. Thank you. Took me a while to understand how to do it, but I got there and I've definitely learnt along the way. The results I have are promising. Though I have to say I can't get the spring constraints to be very stable. I've played with strength, damping and mass. I can only use low values of strength, before pieces start popping to the ends of the universe on frame 2. So I use low strength, and quickly delete the spring constraint before the pieces start looking like they drooping away, and it's enough to start a tumble on most pieces. Travis, I'm not sure about the noisy point velocities - can't picture how that would give a tumble in the right direction/axis. But the random cubes placed right under pieces and deleted away just slower than the constraints. Brilliant! What a simple, but effective idea. I will post back with more results. Sim.
  10. Hi all, I have an voronoi fractured terrain and in classic fashion, there's a crack through the middle and the pieces start falling from the central crack down into an abyss. To get the falling propagating outwards from the middle, I'm using a Glue network and dissolving the constraints outwards over time. My object is an RBD packed primitive . This all works, but the pieces tend to fall straight down as their constraints dissolve. I'd really like to get the pieces to tumble as they fall. So that just as the piece is about to fall , the exposed side closest to the abyss - starts to tilt down before the whole piece gives. I'm stuck at this. I've tried simple things like increasing friction. I know one way to do this would be to model a lip on the bottom of every piece facing the centre of the terrain. But doing that by hand would be prohibitive. Does anyone know how I could approach this? Sim.
  11. Hey thanks a lot. I remember looking at the debris tool a while ago out of curiosity, but didn't need it then time and promptly forgot about it. I've had a quick squiz, and it looks to be very close to what I'm looking for. -Sim
  12. Hi, Couldn't find anything on this, but I have a landscape that I've voronoi fractured. It's falling away piece by piece. I want to have sand (particles) falling from the edges of the exposed pieces. I know how to generate an edge attribute for each piece. But I'm hoping someone can help me with how I can find each exposed piece? -As pieces of the landscape drop away. New edges/primitives/points become exposed. How can I find these? I'd appreciate any input on this. -Sim
  13. Just an update, I've come across the idea of clustering and pyro tank instancing. I'm in the middle of working out how to implement it for my particular case and I'll come back with my results. (Also let me know if I've posted this in the wrong area.) -Sim.
  14. Hi all, my scene is of a cracking landscape comprised of a fractured rbd simulation. The pieces of terrain falling down into an abyss. I'm using the 'billowy smoke' shelf tool to create smoke for the falling pieces. The division size I'm using (0.25), is taking about five hours to simulate the 900 frames I need, however that's producing around 100GB of bgeo cache data! And I'm not getting the level of detail that I'm after. I'm happy to do substantially longer sim times. But I'm not sure I can afford the massive file sizes I'll end up with. My plan had been to use this 100GB of data to drive an upres simulation - that I wasn't going to cache out but rather have each farm computer do their 100odd frames worth on the fly as they do final rendering. I'm not sure this is the best way to go about doing it? I'm open to any ideas on how I might better approach this. I'm only simulating a foreground area that's the first couple hundred of meters (of an area that stretches 3km to mountains.) I've tightened the pyro tank as much as I can. I'm using a fixed size. (I deleted the auto-resize gas node) I'm relatively new to pyro fluid sims. I've experimented with the upres shelf tool on simple sims. It works fine, but I'm not sure how to use it with a bgeo cache. For starters I can't seem to fully disconnect it from the lowres sim. In the upres node itself I can set the 'source' to a bgeo file sequence. But deleting the lowres dop network causes the Upres node to error. I can't find the remaining links, and I'm not confident that the lowres sim isn't being recalculated at the same time. I'd appreciate any help on dealing with a large scale smoke sim like this. 'regards, Sim.
  15. Splash

    Sorry probably the single most unhelpful response you could have hoped for, but: That sim looks great. What else would you hope for?
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