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Everything posted by anupamd

  1. Just curious if there is a way to control simulation attributes per point? For example, if I have a fluid flowing over a surface, and want the friction coefficient of the surface to vary across the surface using a noise pattern..so that the fluid breaks up in an organic way as it flows down. (this would be a nice way to get good detail without using complex collisions) Perhaps another way to do it is to vary the separation scale per fluid particle, to get a sort of per-particle viscosity. Or.. perhaps if all we are doing is modifying the divergence field, some way to modify the existing divergence field to get the desired result? Either way, these are great ideas however I do not see a way to get at the data and manipulate it. I dont see this data existing as a scalar/vector field anywhere. Any help would be great thanks! - Anupam
  2. Pyro fire RnD and questions.

    well Im trying to sell my team on using houdini for fire and smoke. First pass at fire here: This is all H12, Movement is pretty good, detail and shading kind of $hit to be honest. grid size is 300x300. Fume/Maya does a better job at the shading and detail bit, Houdini seems to have more realistic movement. Next step is to see if uprezed fire looks good or not. (this fire sim is not uprezed) Also the pyro shader is just horribly slow. Sim time here was 10 minutes which is amazing (Im using OpenCL HW acceleration) BUT..8 HOURS for rendering without any scattering???. I played with the voxel step size to no avail. Thats a bottleneck. Does anyone out there have a decent fire shader (something just kitchen sink) that doesn't soak up gobs of time?
  3. So I've never had much luck using rest fields in pyro to add more detail via texturing. However the technique of advecting particles through the fluid and carrying over the local coordinates seems really promising. my question is how would one approach this? Seems to have worked amazingly well for the Main Road Post guys: "ultimately they determined that their best course of action was to run most of their Pyro FX simulations using advected particles inside volumes and then carry over the local coordinates. Taking this route allowed them to find the sweet spot they were looking for." rendered results: article from; https://www.sidefx.com/index.php?option=com_content&task=view&id=2692&Itemid=68
  4. Im trying to grab the nice flip color visualization in SOPs. If I file cache out of dop-import in SOPS I loose the color after the file cache node. Where is the color coming from and how can I use it in sops? *see attached*
  5. I tried to follow Scott Keatings foam shading tutorial exactly for rendering points as volumes using the vex volume procedural. But it does not work for me and I cant figure out why. Could someone take a look at my hip file and see what im doing wrong? (ps: in trying to render flip foam with this technique)
  6. vex volume procedural not working on points.

    Anyone? Is no one using uniformvolumes to render points for stuff like foam for your flipfluid sims?
  7. vex volume procedural not working on points.

    Also, I it does work if I create a volume with the points (eg: via volumerasteriseaspoints), etc.. but I do not want to do this step as it is very slow for millions of particles. As per scott keatings tutorial, you just need the points and the shader to render each point as a spherical volume blob, and that is what I am interested in.
  8. vex volume procedural not working on points.

    oops.. here is the hip file. uniformvolproblem.hip
  9. Hi guys, I would love to use PointReplicate to do krakatoa like point rendering for my splash and foam elements of my flip sim. The issue is that I randomize the input points based on pointID (each ID gets a different seed for the randomization). The problem is that with foam/splashes the point id's change ( I think.. no?) . So how does one use pointreplicate with changing Point ID? Is tehre another attribute ont he particles that do not change that I can use instead? Thanks!
  10. ah hah.. that makes sense. duh.. Thanks!
  11. Hi guys, I've seen some topics related to this but none of the suggestions have helped. so here goes I have a relatively simple object (roughly a box), that im fracturing with voronoi fracture then pushing off to the side with a windforce. The issues is some of the pieces that are really small are getting a really huge velocity. If I disable compute mass in the physical attributes, then it all works. So I have a feeling its because of very small masses that the problem is ocuring. Is there a workable solution to this that does not involve deleting the small chunks before the sim? if not: how does one go about identifying the small pieces for deletion prior to the sim? Also here are things i've tried that did not work: 1. adding a drag force 2. more substeps, 3. double checking convexity in collision 4. shrinking down the collisions slightly Any help would be great, thanks!
  12. also I noticed a lot of guys using packed prims with a pointwrangle DOP to limit the velocities, problem is I cannot use packed prims for other reasons.
  13. I know to some extent this has been discussed on other threads but its not clear to me. To what extent does Flip , Pyro, and RBD use multi-core processors? Is it necessary to tweak any settings to optimize for multi-core machines. If so is there any documentation available for this? I am currently building a dual 6 core intel I5 and want to make sure im not wasting money on the dual proc if houdini is not even going to utilize the multi cores. Thanks,
  14. Flip, Pyro and RBD with Dual- multi core processors.

    Thanks for the info Ian. Another quick question. I have the option of utilizing a dual 6core 2.6ghz or a dual 4 core 3.5ghz. Not sure which to get as im unclear as to if the number of cores will win over raw horsepower per processor. Any opinions on the matter would be helpful. - Anupam
  15. (kudos to Matt Radford)First check this out, 3DS max + thinking particles / volumebreaker. This is seriously good guys, we should be able to do this with houdini... the physics is fairly straight forward with gluenets and bullet, but the issue is the fracturing and getting that to look natural. Has anyone looked in to fracturing geometry without using voronoi? The fragments that voronoi produces often look un-natural and sort of rock-like. Im interested in coming up with a solution if none exists, and I thought I'd start a thread about it. So one solution is to go through a for-each and chop up geo with cutting planes, this has been attempted before by others on odforce.. but it seems to be that the cookie sop produces bad geometry and is UN-reliable. I believe there was talk of "fixing" the cookie sop but clearly sidefx hasnt done anything yet... so there is there bottleneck . Is there a better cookie sop out there somewhere?
  16. proper height map in a shader

    I cant believe Im having issues with this simple shader: Trying to get a height map (well its actually a z-depth map) that has a very narrow range. For example my furthest point is -2 on z and the nearest point is +2 on z. I want to generate a greyscale map that has a value from 0 to 1. The math Im using is just pz-farplane. in this example our values will range from 0 where z is the farthest point and 4 where the point is at the near plane. if I use a fitrange and remap the values 0->4 to 0->1 i should get a nice smooth ramp. But that is not working. Is there a better way to do this or a shader that already exists? Thanks,
  17. strange artifact in pyro render

    So its funny, I've been noticing these streaking artifact in my pyro tests I've been doing lately. Was browsing vimeo and saw another guy having the same exact issue. I always seem to get it when using a lot of shredding with large grid sizes and cant seem to get rid of it no matter what. Im seeing this over and over again any time I use shredding, so Im wondering if there is something funky going with the solver. Check out this video; Go to 00:32 ps: Props for these tests go to Meradi Omar, these are not my tests. -A
  18. non voronoi more realistic fracturing.

    Well i think what Macha means is deform the space that the fracturing takes place. See attached HIP. So yea, you can do this now by just deforming the object, fracturing, then deforming it back. Here is a quick example of that I came up with. I have to say it looks way better than I expected.. and actually looks better than the odd looking voronoi patterns. Im playing with other techniques too and I'll post sample hips here if I come up with anything interesting. .. now if I could only figure out how glue networks work.. argggh! fracture_deform.hip
  19. So I've got a simple morph form one shape to another. I comb the normals slightly on one of the morph targets and it ignores my combed normals when I morph. I would like the normals to rotate as the object morphs. How do you do this? Do I have to re-calculate the normals manually (by converting to tangent space..etc) Take a look at my hip it will be clear? morph_normals.hipnc
  20. Sphere-sphere collision in VOPPOP

    you could just do simple sphere collision in bullet.. its probably about the same speed as if you did it in POPs.,.. Im guessing.. not that I actually tried.. but I probably should
  21. Does anyone know have any info/docs on .geo/.bgeo file format as it relates to volumes. The current docs don’t really say anything about how volumes are stored (other than they are primitive attributes). I am trying to export velocity fields out of a fluid sim for use elsewhere and writing these out of Houdini as .geo ascii files. For a 10x10x10 volume we get 3 data blocks (one for each dimention). That makes sense to me. But for a 20x20x20 we get 8 data blocks per dimension, which I cant make sense of. Attached are the two files. If someone knows more about how volumes are written out to .geo files I'd love to speak with you further. Any assistance would be appreciated. See attached. pyro_velexport_debug.hip
  22. Wow this is great help an will also check out additional documentation in UT_VoxelArray.h. Ok I will try that out! Thanks so much for the speedy response! ps: need to export velocity fields out of houdini for use in a seperate propritary application (not houdini).
  23. nissan altima - wouldnt be cool

    The cubes thing: pretty standard houdini pyro with advected particles, then copysop with cubes. The wires thing is carve sop with wire sop. See attached examples WIRE_SOP_EXAMPLE.hip advect_particles.hip
  24. Hi guys, is there some trick to converting or "flattening" a mesh into its UV space representation. Essentially the same thing that this does: http://www.scriptspot.com/3ds-max/scripts/uv-2-mesh The reason why I want this is that I'd like to do some modeling transoformations on the UVs themselves, and then render an image from UV space. Essentially Im sort of generating a normal map. There still doesnt seem to be a good way to do this. Im hoping someone has been down this path and found an ideal solution. Attached is a pic of the object and the UV layout.. you'll get a better understanding once you see the pix. ps: i know I could just bake a normal map in maya..etc.. or use that max script from scriptspot, but I'd like to keep this process in houdini if possible. - Anupam
  25. clever trick to convert UV to mesh?

    Dennis, ****I just fell off my chair**** I cannot believe how obvious of a solution that was. LOL. 3DSMax = Plugin. Houdini = Just a point sop. WINNING! Thanks a million...