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Everything posted by jamesr

  1. Can't Get Rid of Particle Stepping

    Whenever you're running into issues like this, it helps to throw down a Timeshift SOP, uncheck "integer frames", and break the connection in the "Frame" parameter. Use the ladder to scrub forward/back in like 0.1 increments. If the source moves smoothly no matter how granular the unit which which you're scrubbing is, you should be good. When you're simulating and you're caching to RAM, houdini has everything it needs to access subframe data (which is why you're seeing correct results when you don't cache your source). When you cache to disk, by default it saves on whole frames. When the cache is read back in, you only have access to what was written to disk, so when you're running a particle sim with say 5 substeps, and houdini looks up frame 1001.2 of the incoming source, there won't be anything there. The Time Blend SOP will interpolate between frames for you. In most cases, it is necessary to have an i@id attribute on your points, since especially for particle simulations the point count may not be stable, and the Time Blend SOP won't work correctly. Unless there is significant motion in between whole frames, it's not necessarily required to write substeps to disk.
  2. pop replicate 1st vs 2nd input

    The second input is "Reference Stream". You will notice a difference if you are merging the replicated points back in. In the left input, there will be double what you expect With it in the right input, the points will be replicated based on the input, but when you merge them back in there will be the correct amount. Check this example, I think it will help. popreplicate_second_input.hip
  3. popdrag - slower particle in selected radius

    Hi, your issue is in the pop drag node. You have "@falloff" in the activation slider, which is deactivating the whole node, because that expression isn't valid for that parameter. Think of activation as like a "global" parameter for the node. It can't be changed per particle, it's either on or off. Instead, you should leave Activation to 1 and use "VEXpressions" to multiply the drag (airresist) by your custom attribute. Also, you have "0.798" as the point number for your distance lookup in the VOP where you set the f@falloff attribute. You should be careful that it is set to the correct point number. Nodes changed are in red. particles_issue_jamesr.hip
  4. Exporting Material Diffuse Animation

    You can use COPs for this
  5. SDF from density in Dops

    It'd be cool to hear from the source, but here's what I figured out fog_to_sdf_dops.hip
  6. And the demo file doesn't work?
  7. Are you using layer mixing in your material? Or are you just trying to write custom aovs?
  8. Split geometry to parts by proximity

    Could you just ray the target points that are on each target onto your source starting geometry and call those the starting points? Then you have the target attribute/group already on the points, and already once they are minpos'd onto the source geo, they will always be as close as they can be to that target.
  9. Split geometry to parts by proximity

    Hmmm if all you care about is distance to the target geometry, you should be able to just assign an integer attribute called like "target" or something, and use nearpoint() and point() to get the closest one. int pt_near = nearpoint(1, v@P); i@target = point(1, "target", pt_near); and do stuff to your particles from there. You could even make them into groups if you wanted string groupname = sprintf("target_%d", i@target); setpointgroup(0, groupname, i@ptnum, 1, "set"); Maybe I'm missing something? close_point_targets.hip
  10. Here's your same setup, only one line different. See inside the SOP solver. Also to see color better you should unpack. SOP Solver Problem_james2.hip
  11. Does this help? SOP Solver Problem_james.hip
  12. You asked how to create your own AOV, which is what's demonstrated in the demo scene. I use some arbitrary noise to write out to their own image planes. Did you hit render and look at the extra image planes? You don't need set/get layer export to write out aovs.
  13. sort by attribute ?

    You can skip all the sorting parts business and just do skin after the merge. You'll see it works.
  14. All you should really have to do is bind export from the shader. Render this bad boy out and let me know if that's what you're after. aovs.hip
  15. sort by attribute ?

    It usually is but it wasn't coming through on my end properly (maybe cause it was an alembic in a normal file sop? idk). Anyways, group promote your edge group to points, or just group the points from the get go and it works.
  16. sort by attribute ?

    Can you reupload with an alembic sop frozen?
  17. Measure SOP Docs might help a bit to explain the curvature stuff. I think you're after the "Mean" method. measure_curvature.hip
  18. drop node on wire

    That's what I've been doing since 17.5. Still kind of a bummer though. You're right, you don't miss it until it's gone!
  19. drop node on wire

    It definitely did used to be the normal behavior. I believe they had to dump it for the new MMB options on nodes with multiple outputs. I'd really like to see it come back. Unless someone can chime in with the name of the preference (if there is one), I think it's just gone...
  20. Hi, this effect sounds neat. I don't know if you'll have much luck with the rigid body solver in this case the way you've got it (I could be very wrong though so anybody please chime in!). Shuffling your DOP setup around and changing the density of the RBD object seems to do sort of what I think you were saying? The torus is affected by the FLIP sim, but in a rigid sort of way. Otherwise, I'd be looking for ways to transfer the motion of the flip sim to the torus in SOPs post-sim. EDIT: Also if you're getting any jittery stuff on your object you wanna smooth out, try just using a little bit of a lag or filter CHOP on P and blend it back in. It can help with some small stuff. meshtest_jamesr.hipnc
  21. Distribute particles more evenly?

    @Krion It appears you piped an iso offset into the popnet. What they meant was to run your sphere into a Points from Volume SOP, then source from that. You can also try turning on the relax iterations on the POP Source DOP. By default it's turned off. Inside the POP Source is just a scatter node, so you can use those controls the same as you would in SOPs. Does this setup help? particles_even_jamesr.hipnc
  22. Transformation matrix object offset ?

    up aim and side vectors won't translate your object. can you post a hip?
  23. Reverse point order only for point group

    Maybe not the most elegant, but does this help? Pt_order_mess_jamesr.hip
  24. I think you're way overthinking it. No need for SOP solver, just turn on "Inherit Velocity from Point Velocity" on the RBD Packed object DOP. Keep it as "v@v" on the points. Is this what you're after? dop_ActiveAndVelocity_jamesr.hiplc
  25. Packed RBD from Pop Sim

    It might help to just think of your packed rbds as particles. You can apply all the normal pop forces to them, so the pop sim is maybe just extra. But maybe you like the pop sim's behavior or something, you could try looking up the point's position, and calculate a velocity vector towards that. Let me know if this helps at all. particleRbdTest_01_jamesr.hip