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About bentway23

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    Mark Reynolds
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  1. This is fantastic--thanks for the pointers!
  2. That gets the shape, but not the changes in velocity--what I'm looking for is the acceleration at the perigee and deceleration at the apogee. I tried basic trig early on, but couldn't translate that into varying velocities.
  3. What I'm looking for is an object to follow an elliptical curve, accelerating near the perigee and decelerating near the apogee. Theoretically I could wrestle with magnet forces and do a sim for this, but I feel that (1) that'd be unnecessarily complicated, and (2) that this is going to be a collider for another sim, and that might muck it up. I've tried follow path and using primuv, but I have not been able to find a way to accelerate and decelerate them as they follow the curve. I've tried something, attached, that is MOSTLY working. I get velocities from the tangent normals of the orbit curve, and a velocity multiplier based on the min and max x positions along the curve, so at the perigee the velocity multiplier is 1 (or whatever), and at the apogee it's 0.1. Using a solver SOP, each frame I transfer the curvevel attribute to the ball orbiting object at its current location, and then use @P += @curvevel. This actually works for the most part, except the orbiting object keeps going further and further out, creating a spiral orbit. Furthermore, even though I have a wrangle setting its initial position to be at point 0 of the path curve, starts farther away.(Also, I will need to figure out a way to orient it so it's always looking forward, but that will be easy enough, methinks.) I assume I'm missing something obvious within the solver SOP. This might be easy and dumb, so thanks for any help. (Also, if there's just a way better way to do this, I'm open to suggestions!) orbit_setup.hiplc
  4. Cool. In this case I didn't actually have a grid, but a very lumpy thing so there were few actual inline points. That's a good thing to keep in mind, though!
  5. Perfect. I sort the points, use a wrangle to delete all but the first and last, and I'm good to go. This requires it to be even with the grid(/surface) in y, but it's easy enough to throw a transform after to raise it up afterwards. Thanks!
  6. That's exactly what I want! What is happening with the intersection analysis and add?
  7. That's actually the reverse of what I want--I want the points to match the edges of the grid (and preferably not move in y). That moves the line in y but doesn't match the length to the point of the grid where it drops down.
  8. I know how to use that to, well, detect intersections, but I don't see any options on it useful here. Is it one of the output attributes?
  9. I have a line hovering above another object (in this example, it's just a grid, but it's more irregularly shaped in what I need). I would like it so that the line length matches the width of the object directly underneath, without reorienting the line, and preferably without actually snapping it to the new point (in y). Ideally, if I could extract a bbox D_XMIN (/MAX) (or a getbbox min.x), but only at the point in z where the line is, then I could just translate the points to that location. I'm sure this is super-simple, but I'm not quite sure how to go about it. A ray SOP gets me in the ballpark, but presents some problems, as in the pics. Thanks! lineray.hiplc
  10. Help/F1 now just pulls up Google

    That just opens Chrome and tries indefinitely (and fails) to load IP address I like it opening in Houdini, it's just no longer opening help, but a Google search window. Also, even though I've deleted the external browser line from the .env, it's still opening up in the external browser. How can I undo that so it's like it was earlier this morning--inside Houdini and pulling up help? EDIT: I changed the 1 to 0 in the .env, saved, restarted, and then re-deleted that line altogether and Houdini is opening help up in the program again, just not actually opening help, still the Google search.
  11. I usually hit F1 for help. I just hit the question mark in the upper right hand corner for the first time, and now "help" no longer pulls up "help," but a tab that searches Google instead of the Houdini help. Since that happened, now it does the same for hitting F1. I've shut down and restarted and it's still doing it. (The tab also tells me it's using an older version of Chrome, which my outside-of-Houdini browser is not.) How can I get Help to start showing, well, Help again? I'm running Houdini Indie 17.5. Thanks!
  12. Grouping points in cached FLIP sim?

    I have a pre-simmed/cached FLIP sim. I would like to create a group of a section of the particles of the sim so I can mesh them separately and apply different shaders to them later. Re-simming is difficult and slightly impractical, so I would love to be able to do this with the cached points as-is(/are). I can create a group of points, but it looks like point numbers are not constant in FLIP sims, as the group changes over the course of the sim (frame to frame, actually). Is there a way to create a group that then remains constant and flows with the existing sim? Or even a way to create a new group of particles that is advected by the existing cached sim? (I'm pretty sure it's no longer a "volume" by then, so I'm guessing a straightforward advection by volume POP wouldn't work.) Or a way to do some sort of "sort" operation to compel points to retain point numbers, which I could then group? Or advecting another form to follow the sim, and I could then use that as a bounding volume to create my group? (Point deforms with FLIP sims as the deformer seem to get really messy really quickly.) Thanks for any help!
  13. Flyaway particles in viscous FLIP

    I had heard that there were gods, wise and benevolent, who walk the earth and visit the forums to ease the troubles of mankind. I was dubious once; now, no longer, for you are obviously such a god. That was perfect. I reduced my viscosity from 2500 to 5, boosted the density to about 5K, and it's exactly what I was looking for! I had been varying the velocity of the emitters, and now they're not just making particles fly away, but rather making interesting, gooey shapes. Thanks so much!
  14. Flyaway particles in viscous FLIP

    I'm running a FLIP sim that I would like to make fairly viscous (read: blood from a wound). If I crank the viscosity high (2500 - 5000) I can see some general slowdown, but the problem is I still get lots of little flyaway particles and after meshing the result still looks very particle-y. I've toyed with surface tension, but have found that it either makes no apparent difference or it just makes the sim explode. Any idea on how I can make my viscous fluid more "stringy"/viscous? The emitter is very small as the scene is fairly small--I actually had to scale up the imported alembics so that the character's head is about a meter high, as "real life" size was too tiny for me to get anything useful out of FLIP. I'm testing at a particle separation of 0.002, doing more detailed tests at 0.0005. Could it just be a matter of cranking those down to ridiculous sim times for it to look less like popcorn? (Unfortunately posting the file isn't do-able, any more info needed I'm happy to supply.) Boosting reseeding to oversampling 48/bandwidth 3 seems to help with the overall feel, but just delays the flyaways, doesn't eliminate them. Thanks for any help!
  15. Using the rayed and then volume-extruded grid in addition to bumping the substeps way up (5 min/10 max), using volume collisions and the RBD solver are doing the trick on my quick test mesh. Haven't tried it on the final big guy yet--I'm guessing more substeps will be in order.