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KarlRichter last won the day on May 8

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  1. crazy bright spots in volume

    Maybe try to clamp the volume rather than absolute value. I know volumes can render strangely with negative values.
  2. "extract transform" SOP is your friend...
  3. hair driven geo deformation setup

    The main advantage to this method is that you can use all the hair tools to setup and animate the wires to drive your deformations. Note that this does not work with instances, as each copy is actually being deformed, not just translated and scaled, by the wire.
  4. Melting geometry, UV issue...

    See attached for an example .hip of a simple method to preserve UV seams in a flip sim: UV_to_FLIP.hipnc
  5. Keep particles inside an volume

    Attached you will find an example of one way to use a volume to contain your particles: howToKeepInside_v02.hipnc
  6. particle position by VOP Mix

    Noboru, Your problem is that you're trying to use a dynamic network when you don't have to. Because your mixing positions in a pop network, you're getting feedback every iteration, making results that you are not expecting. You really don't need a particle system at all to achieve your goal (see what I did there ;-). Check out this modified file for a solution using just a point vop. goto_smooth_v002.003_mix.hipnc
  7. Packing tiles for mosaics

    A while ago, I was working on a project that had lots of animated tiles. It is actually quite a tricky problem to pack a bunch of shapes together with the smallest amount of "grout". While researching this, I stumbled across this paper "Simulating Decorative Mosaics" by Alejo Hausner, and thought this would be a perfect thing to implement in Houdini! Here is the input, the houdini logo: Also needed are curves that represent the color or element boundaries: Here is one iteration of the loop. This is basically the result you would get copying tiles using a scatter and copy sop: After running the loop for fifty iterations, the tiles seem to be pretty well packed, and are respecting the boundary curves very well: And lastly, here is a version with randomized tile sizes. Still works pretty well! While I never actually ended up using this in production, But I thought it was pretty cool and could be used for other stuff, like maybe packing houses in a procedurally generated map or something. Anyway, here is an example .hip file if anyone wants to play around with it: mosaics_example.hip
  8. hair driven geo deformation setup

    I have used this setup on a number of projects and thought I would share. Basically, it is a simple setup that uses the wire deformer and hair system to animate geometry. I used to do this all the time back in Maya using Shave and a haircut, and was surprised that there isn't a more straightforward method to do this kind of effect in Houdini. This is especially useful when you need to add flowers or other kinds of detailed grass to an existing grassy field that has wind blowing through it. grass_example.hip
  9. Vellum substep issue.

    Increasing the pscale without changing the constraint length is what is causing this sim to behave strangely. When the pscale is increased, it is making the sim fight against the constraint length and creates interpenetrations. At low substeps, the behaviour is not as noticable, but is still there (run the sim with the gravity off to see what I mean). This could be solved in a number of ways: - Turn off self collision. - Use another sop to run over the constraint geo and increase the length along with the pscale. - Turn down the stiffness of the stretch constraint.
  10. building 3D frames from mesh geo

    In 17.5, the measure sop has been improved. If you set the measure type to "curvature" and "Principal", you can then choose to output a direction vector.
  11. Evenly Distributed Hexagons On A Object

    Here is a cool trick that will work just for hexagons. Use a remesh node to turn your mesh into nice even triangles, then use the divide node with "compute dual" checked. Instant hexagons! Edit: Well, never mind. I guess that makes some pentagons too. Oh well...
  12. keep uvs on flip anim

    A while back i was playing with the UV fluid mesh seam issue with some amount of success. See attached for an example. uv_fluid_mesh.hip
  13. Your scene is using some external hda so it doesn't open right for me, but I suspect that you are over the geo display limitation. It is very easy to go over this threshold with instances because it's so easy to make so many of them! The default is set to 20 million polygons in the display options -> optimize tab.
  14. Liquid mix export to Maya-Arnold

    To be able to access alembic point data exported from Houdini in Maya with Arnold, you must export the attributes as vertex color data. The trick here is that it MUST be a color type attribute in houdini, a regular vector will not work, and it MUST be a vertex class attribute. So if you were to create a color node and use one of the RGB channels as your "weight", and then promote it to a vertex attribute it would export properly. In order to access this data in Maya with Arnold, you need to check the "Export Vertex Colors" box under the Arnold tab on the alembic shape node. Then you can use the "aiUserDataColor" node in a shader network to put your weight attribute to work using a ramp or something. Also, you can get motion blur data from alembic files with changing topology this way as well. Export your velocity vector as a vertex color and then use the "motion vector source" attribute on the shape node to access the velocity data.
  15. Grains - how to make 'em bounce off surfaces

    Look closer. I know it seems like setting ispbd to 0 would disable the grains entirely, but it doesn't! The particles bounce, but still maintain distance. It's hard to see in your test scene so I made one that illustrates this better. ispbd_test.hipnc The ispdb flag does not disable grains, it is there to tell the pop solver that a given particle is under control of pdb, so don't apply all the regular pop physics. Indecently, before I was aware of this flag I would fake a bounce by giving each particle a random upward velocity on the first impact.