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Everything posted by jamesr

  1. If you have two boxes plugged into a merge node, you can select the box you want in the network editor, then hit "enter" in the viewport to get the handles for that box.
  2. krakatoa style rendering

    A lot of the look comes from the sheer amount of tiny particles. Krakatoa uses a concept they call partitioning to render particles over and over again with slightly different positions. You can do the same in houdini with wedging by randomly varying a seed value in your particle sim for each time the wedge is run. This lets you design one sim, then run a bunch of wedges (like partitions in krakatoa) instead of directly simulating potentially millions and millions of particles all in one go. If you want more detail, simply add more wedges! You can then load all the wedges at rendertime and get a very similar result. A couple of things that can help push the look are both tweaking the Alpha attribute of your particles, and adding a volume around it to help fill in the space.
  3. Oh ok! You should be able to head to your group sop, and on the very far right of the "Base Group" parameter there's an arrow pointing up. Click it, then shift+select the new points the viewport and hit enter.
  4. Do you mean add points to a group selection like in the group parameter of a node where you can isolate the effect of the node to just those points? Or are you actually creating a group and need to add points to it?
  5. Clean Growth PolyWires, Tutorials?

    Here you go: Curl Noise Flow - Entagma
  6. houdini alembic to maya problem

    Which renderer are you using?
  7. workflow for flip fluid sim/mesh/render

    Yup! They've got some example scene files you can download, too.
  8. Ramping into a group in POPS

    Try using a fit() function to remap the age, then scale the force itself by that. Should be possible in the VEXPression section of your POP Force. You don't even need to put the particles in a group (unless you want to). float newage = fit(@age, 1.5, 3, 0,10); force *= newage; This will ramp the force from 0 - 10 as the particle goes from age 1.5 - 3. Before that, the force is 0. Same can be done with "amp" in the noise section.
  9. You could copy/paste it into an empty houdini scene, then open that and copy/paste. Or simpler you just make the shop into an HDA and save it someplace and load it in.
  10. Ash and Disintegrate in Houdini

    I haven't watched it, but check out Peter Quint's peeling tutorial. It looks like a similar effect for the ashy part. You could probably get similar motion if you emit smoke from your object (sphere or what have you), shape the look with some initial velocity/forces, and advect the points through the volume. Search "advect points through volume" to get some info on that. Also, look into voronoi fracturing to get a pattern for the pieces to break into, VOPs and various types of noise to break up straight edges and for shading (need to know vops for everything!), and maybe the wire solver (or maybe springs) to give the pieces some organic feel. If you're getting started, check out Matt Estela's page http://www.tokeru.com/cgwiki/?title=Houdini It's an amazing wiki with a lot of the best info and links for learning houdini. Good Luck!
  11. workflow for flip fluid sim/mesh/render

    That looks correct. You can leave "load from disk on" even if there's nothing on disk. It will error at first bc there's nothing there, then it will write and load from that location.
  12. workflow for flip fluid sim/mesh/render

    That's the standard workflow using the shelf tools, which should be just fine. If you want to go straight from sim --> rendered frames overnight, you can set up a dependency of fetch nodes inside a ropnet. A "Fetch" ROP simply looks for a "ROP Output Driver" to render. If you have multiple fetch nodes piped into a "merge" ROP, it will render them in order left to right. I would suggest: Make 2 Fetch ROPs and 1 Mantra ROP, and a Merge. Name them something useful (ie: "fetch_flip_particles", "fetch_surface", etc) In the first Fetch, click the dropdown and navigate to the filecache node that write the flip particles. Inside that, there's an Output Driver called "render". Select that one. In the second Fetch, do the same, but for the flip surface cache. Configure your desired mantra render settings in the Mantra ROP From left to right, wire the nodes particles, surface, render. Order counts! On the merge node, hit the Render flag button on the right. Important! There's an option that says "Frame by Frame". You will want to change this to "node by node", so that each node is dependent upon the one to the left of it to finish before it can start. Grab a beer, have a nap, and return in a few hours to comp your frames! You can do this with any cache that depends on another to be finished in order to produce desired results. I hope this helps.
  13. Hey I know you were hoping for a scene file earlier, so here is one I made for you. I hope this helps/is what you're after. sourcevolume_collisions_for_tagosaku.hiplc
  14. @tagosaku You say it's like it's not colliding at all right? But you can see collision geo when you enable the guide on the FLIP Object? Is your sourcevolume DOP wired into "sourcing"? If so, try switching it to the third input, "Volume Velocity". I'm unable to send a scene atm.
  15. If using a VDB surface with the Source Volume DOP for collisions, you need to switch the "Source Volume" Parameter from 1 to -1
  16. Advecting Pyro with Object (Help)

    Have you tried doing a Trail SOP on the skull, converting to VDB w/velocity and sourcing in DOPs with a 'Source Volume" set to collision?
  17. Animate pScale of flip overtime?

    *= is a shorter way of saying @pscale = @pscale * 0.99; The wrangle evaluates at every timestep, so each time it does, it makes pscale be only 99% of what it was on the previous time step. That will make it get closer and closer to zero.
  18. Try: npoints(opinputpath(".", 0))
  19. Solver SOP and substeps

    should be on that last line @Cd.x *= decay_val * @TimeInc;
  20. pop gravity node

    I'm not sure I fully understand your intent, but you could try grouping whatever spray particles you have, and adding a POP Force on just that group, or set a rule in the VEXPression section of a POP Force to single out the particles acting as spray by some attribute or another.
  21. Solver SOP and substeps

    You need to multiply decal_val * @TimeInc to make sure that substeps are being taken into account, or else it will evaluate that every timestep and will decay much faster the more substeps you add.
  22. Have you tried plugging the .sim frame into the dopnet's initial state parameter?
  23. Hey! This can be done by hooking up a Pop Force into the "Particle velocity" input of the FLIP Solver. Let's assume the left part of your fluid is on the Z+ side and the right part is on the Z- side. Inside the Pop Force, you can check the box that under force that says "Use VEXpressions" and enter something like this: if(@P.z<0){ force.y = -9.8; } else { force.y = 9.8; } This will cause all the points on the right side to fall, while the left half rises up. Hope this helps!
  24. move pivot to specific point

    Hi! If I have a polygon sphere, and I want to put the pivot of my transform sop to point number 30 on my sphere, I would write like so point("../sphere1", 30, "P", 0) point("../sphere1", 30, "P", 1) point("../sphere1", 30, "P", 2) You're trying to do "P.x". The function is looking for an attribute, so you just need put "P" for position. Since position is a vector, it has 3 components which are what the last number in the function refer to. 0 for x, 1 for y, and 2 for z. Hope this helps!
  25. Flip with multiple layers of liquids

    If you're trying to mix something around like blood/water, coffee/cream, oil, etc, you can try using the density+viscosity parameters in the FLIP solver and see if you get desired results. You could do a "points from volume" and source that in as a particle field in the flipfluid object, and create an attribute on the points in SOPs called f@density Then turn on "density by attribute" in the FLIP solver. EDIT: After re-reading your post, I don't think I really answered your question as I don't think density by itself will cause the two viscous fluids to rub against each other...