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Everything posted by art3mis

  1. Multiple Vellum Solvers?

    Have gone thru the Vellum Masterclass, the THUG presentation and all of Entagma's introductory vellum tutorials. Still a few questions. If you have multiple separate clothing items on a single character, is it considered 'best practice' to have multiple vellum solvers, one for each piece of clothing, or is it necessary to merge ALL clothing items before using a single solver? Also, I've read the documentation in regards to Stitch Points and Weld Points constraints. http://www.sidefx.com/docs/houdini/nodes/sop/vellumconstraints.html They both seem to be somewhat interchangeable. Can anyone provide an example of when you would use one over another?
  2. Yes the Volume Tab. AFAIK for a Spot light its the only place you can enter Samples.
  3. Created kind of a render torture test. All that is missing is caustics! Would appreciate some expert RS feedback on some starting settings to try for a quality render. Assume I will be enabling motion blur on the water droplets as well. In this simple scene are there any advantages to setting samples at the Material level (water, glass)? Using 2 Dome Lights, a Volumetric Spot and slight accent with backlight area. glass_water_volumetric.mp4
  4. OP Edited post to include 2 images. Getting a lot of noise and fireflies in the reflections. Again 2 dome lights 1 volumetric spot with 1024 samples ray contribution Uniform Settings 16 min 512 max Adaptive error .01 Sample Filtering Gaussian 2,4,4 GI disabled.
  5. Thanks. Will try and post a higher res frame once I am closer to completion. So I assume no need for GI?
  6. Any CHOPs experts? How do you enable MotionFX but only to start at a specific(current) frame? Simply keyframing in the main timeline doesn't work.
  7. Thanks. I am using the proxy volume so I guess I am ok.
  8. Question about proper way to animate your geometry when using for collision. If you animate some geometry and then use an Object Merge to bring this geometry inside another geo where you create your collisions (using either Collision SOP or VDB From Polygons) ,does this mean in essence you are recreating your collision VDBs on every frame? AFAIK the important thing is that your collision VDBs contain correct velocity values.
  9. If your simulation is using substeps can anyone confirm whether its necessary to also cache your source collision VDB's with substeps (ie using $FF instead of just $F) ? The cached collision VDB's then being referenced by the Static Object DOP in your DOP network.
  10. So used Collision separation override but still have issue. Through trial and error though I think I am getting closer to figuring out why. In 2 tests with the exact same settings, the only thing I changed was the Collision Separation override on my FLIP Object. When it was set to .5 * Particle Separation the simulation fails at around frame 100.(the particles rapidly drain away) When it was set to .25 * Particle Separation the simulation fails on or around frame 40. I checked and OpenCL is NOT enabled on my Solver. The issue seems to go away when I have a coarse Particle Separation of .05 or more. What else could be causing this? Is this possibly memory related?? Launchv12__FLIP_Failure025ps.mp4
  11. AFAIK the ONLY difference in the 2 attached simulations is that in the 'failed' one I have simply reduced my particle Separation from .05 to .025. In each case the resolution of my collision VDBs is directly tied to this resolution. WTF is happening? What should I try to fix this? I need the increased resolution. Pulling my hair out. Launchv11_025ps.mp4 Launchv8_05ps.mp4
  12. Thanks. Will try enabling Collision Separation override and using ch("particlesep")*.5 as a start.
  13. Thanks. Still gaps in my full understanding of FLIP but wouldn't decoupling in this way mean that your collision resolution would be 'coarser' than the particle separation and make the issue worse? Just to clarify I've created a custom Voxel Size parameter on my Flip Object which is a product of Particle Separation * Grid Scale It is this custom Voxel Size parameter I am linking to on my Collision Source SOP>Volume>Voxel Size The problem seems to happen when I increase my resolution (reduce particle separation and hence voxel size).
  14. With fast moving collision geometry and FLIP, what are some things to try to stop fluid from passing thru your geometry? Things I've tried - increasing substeps (using 8 currently) - reducing particle separation (I'm at .01 currently) What else should I try?
  15. Proper scale for FLIP

    So this has been mentioned in a few other threads but need some guidelines. My understanding is that FLIP has issues (unstable, flickering, collision, etc) for "small" scale simulations. By that I assume means anything under roughly a metre in largest dimension. What are some suggested starting points for scaling up your simulation for FLIP if its say, roughly a foot or so in diameter. 3X? 10 X? And what about speed to compensate. If you increase the scale 3X do you also need to speed it up 3x as well? There is also Spatial Scale on Solver and was wondering as a first step if i should try reducing to say .1 before I do anything else?
  16. FLIP- fluid going thru collision geometry

    Thanks Atom! Will have a look. Went thru the Collisions Masterclass and seem to recall problems with leaking fluids but no 100% solution. After reading the thread also had the same question as OP, re POP fluids, especially for table top size FLIP sims. I notice in the animated gif the fluid never leaves the container, even when upside down. Is this expected behaviour?
  17. For better collisions of fluid with geometry with FLIP, should you add your substeps on the FLIP Solver, or on the parent DOP Network?
  18. Out of sync collision mesh and fluid

    Attached fileUpload.hiplc
  19. Have a frustrating problem with a simulation involving a rotating cup mesh containing fluid. The collision appears out of sync and is worse with increased velocity. I've already solved most of the collision issues (I think) by increasing both voxel density (using particle separation of .01) and simulation substeps.( using 8 currently). The cup in this case is an inverted pyramid. The motion is oscillating rotation in y axis, think 'washing machine'. The attached Top View mp4 should make this clear. Something to do I assume with the velocity of the collision vdb(cup) being passed to the fluid particles or...? Anyone care to diagnose what is happening? simulation_collisionOutOfSync.mp4
  20. Out of sync collision mesh and fluid

    Here's just the first 120 frames with the premesh particles and actual collision vdb. I reduced the Collision Velocity Scale to 1 from 1.5 which seems to help a bit but still an issue. I am wondering if its another setting in my FLIP solver I need to play with? collision_sync_v2.mp4
  21. Normals not normal

    Thanks Henry. Makes a lot more sense.
  22. Can any uv, modelling experts have a look at my geometry in the attached and tell me if my Normals are 'ok'? The geometry is an inverted pyramid shape hollowed out. I should have a normal perpendicular to each face in my geometry which deosn't seem to be the case. I'f tried every setting on the Normal SOP and nothing seems to make a difference. Also, when do you know if you should be applying normals to vertices, points or primitives?
  23. Moving Liquid in Glass

    Thanks! Great tips.