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Hi, So I have a pop simulation project where I'm using a curve and a custom force in a volume to advect some particles. When the particles reach a certain point, I would like them to continue moving in the general direction, but not be 'stuck' to the popadvectbyvolume volume at that point. Can't seem to figure out how to get that working. I've tried groups and popstreams, but they are not working as expected. Thoughts? Thaniks, Jim

There is an enhanced scatter and align node with additional features. https://www.sidefx.com/docs/houdini/nodes/sop/scatteralign.html

Hi I'm running into this issue where my agent's footlocking is returning the feet back to the original location and not snapping to the nearest part of the grid. This is a stationary walkcycle and I am translating it forward which might be the problem. I attached the file. If you can help that would be awesome! scorp.hiplc

The point relax-node tries to achieve this. https://www.sidefx.com/docs/houdini/nodes/sop/relax.html

I appreciate your confidence in me - and the suggestions. I need to spend some serious time learning about constraints and dops, however... I think I just found a solution that may work in this case. Took me a while but I figured out a way to manipulate the constraint geo, which is with a "sop solver (constraint geometry)" node. Brought in the point scatter the same way as with the geo sop solver to get the wave force, then the constraint prims are deleted if the waveforce is above a certain value. Not sure if this is the best way to do it but since it seems to be working, I'd consider this a success. Thank you! customForces_v12.hiplc

Here's the same scene after playing with a few parameters. Lower density and gravity. Also played with the glue release control. ap_hard_glue_wall_breaking-2_040325.hiplc

Hey everyone, I want to scatter points on a surface while dynamically adjusting their distances based on the "pscale" attribute. When I change the "pscale" value, the spacing between points should automatically update to reflect the new scale. Any suggestions on how to achieve this? Thanks for helping. Points Pscale.hip

Maybe you could reverse engineer something like this. ap_hard_glue_wall_breaking_040325.hiplc

Hey Atom, thanks for checking out my project. I'm not exactly sure what the secret sauce is here but to me it seems like there's no longer any constraint geometry, even when turning off the waveforce node and gravity on the bullet solver. I'm imagining my goal as something like if waveforce > threshold, break constraint, so I'd like to keep the constraints until waveforce breaks them, if possible. And maybe this is too much to even say but another component of this will be the lack of ground and not having gravity affect the pieces until the constraints are broken, but maybe that part will come for free after the constraints, idk. Appreciate it!

Rig the tree with kine fx , animate the rig . convert Line the rig add vellum glue and vellum hair on freezed rig. Add attatch Geo constraint for attaching hair to your anim rig and setup stiffness Attribute there . Try Point deform to apply Sim /anim combination now Back to non abimated rig

You can keyframe time scale. Applying more force will auto-break the constraints. ap_customForces_v09.hiplc

not

A kind sir helped me with a tip to use attribute transfer node instead of vex. Been a minute since I picked up Houdini, apparently. Updated is attached. The forces are being transferred so the issue now will be figuring out how to break constraints / have gravity affect the pieces only once they reach a force threshold, or something like that. customForces_v09.hiplc

In the dopnet > sop solver > wrangle, it seems the nearpoints function only actually finds neighbors of point 0 for some reason... That might actually be my issue rather than not reading each frame.

Fixed! Fantastic, thanks so much for the advice, and the file. All makes sense.

Hey thanks! I'll check this out and report back :-)

uv_transfer_with_seams.hip try a for each loop

Wondering if there's a technique for this? I've got a megascan model with a bunch of UV islands. Convert to vdb, do some stuff then convert back to polys with the UV data along for the ride, then extract the UV data and re-apply it to the mesh. Works great, except at the edges of the UV islands - the UV points are all connected so there's glitches. I've made an edge group for all the stretched edges, selecting by length, so I've got them isolated and the UV islands look intact. But after that I'm running out of ideas - hopefully this has been solved before! Thanks :-)

Thanks! ill check out your notes, normally i would work with particle Cd attribute but i was worried that i wasnt the best approach if i wanted to see that mixing inside the fluid, not only over the surface so i thougt that maybe doing the process with volumes would allowed me later to obtaint a volume field that i could render but after some research, i think i might need a differetn sim witch pyro to "emulate" that effect...

Hello, I have a primitive string attribute: Bridge_Small_Dark_01 I need to procedurally extract the part of the string before "_Dark". Using split it seems it only accepts singular symbols as a separator (eg "/"), I need to find a way to use the specific string as the separator. Using s@name = split(s@name, "_Dark")[0]; does not work. Is there another function I should be looking into? EDIT: using "_" as separator and using [0] + [1] etc in split would not work since not all assets have the same number of words before "_Dark" EDIT2: Big thanks to Tomas Slancik for answering this on sidefx forums. Answer below: use re_split() [www.sidefx.com] string s = "Bridge_Small_Dark_01"; s[]@split = re_split( "_Dark", s );

Hello, I'm trying to create an outward glass shatter effect similar to the helicopter crash scene in The Matrix. So far I have rbdmaterialfracture > rbdconfigure > rbdbulletsolver and on a separate branch is a point scatter with velocity attributes I want to use to affect the glass sim, but I'm having a few issues with that (I'm a sim noob). The first problem is that I can't get the bullet solver to read the velocity each frame. It seems to read the first frame in which there's a non-zero velocity value but stops after that. If I crank the velocity on the scatter points, it seems like mayyyybe the other frames are being brought over, but not as clearly as the first frame and the sim sometimes just stops after a few frames... Secondly, I'd like the glass to have glue constraints and I just learned glue can't be broken with just forces, or they'd have to be manually broken. There's this tutorial that seems to be exactly what I'm looking for, but I get lost when trying to follow it in 20.5. Does anyone have any resources that could help me bridge the knowledge gap there? He breaks glue constraints in a sop solver within the bullet solver at 16:22. https://www.youtube.com/watch?v=fzRJcGFuPXU&t=982s Attached simplified file with my issues. Inside the bullet solver are only my best attempts... Right now I'm just trying to get the velocity transferred each frame so I turned off constraints in the rbdmaterialfracture node and gravity on the solver. It might not come through in the project file but a visualization marker for @v would show the effect I'm going for on the point scatter and also the transfer problem on the bullet solver. Any help would be greatly appreciated - Thanks for taking a look. Robert customForces_v06.hiplc

timeshift and then attrib copy to anim. . maybe send an scene example then i can fix it

Hi Everyone I'm studying the FLIP solver a bit in depth in my free time, going node by node and reading a bit of theory. However, there is a part that I can't understand and I hope you can help me understand the logic. I often read in the literature that in transferring velocities from Lagrangian particles (v@v attribute) to Eulerian grids (v@vel field) a sort of weighted average is made taking into account the velocities of the nearby particles. Example: https://nccastaff.bournemouth.ac.uk/jmacey/MastersProject/MSc12/Ioannidis/Thesis.pdf (page 43), here an abstract: In other more detailed cases the kernel functions are described numerically, for example: https://nccastaff.bournemouth.ac.uk/jmacey/MastersProject/MSc16/01/thesis.pdf (page 12) Or http://alexey.stomakhin.com/research/siggraph2013_snow.pdf Given this, let's say I have a point cloud with certain attributes (v@v, @mass, @pscale), my main questions are: - Does the Gas Particle to Field, when rasterizing the velocities of a point cloud, already perform a weighted average taking into account the velocities of nearby particles like described in above abstracts? - If so, how and what are the mathematical operations behind each option? For example, reading the houdini documentation, does the Accumulated option take into account these kernel functions: - What could be a code/pseudo-code to compute the weighted average of the contribution of nearby particles based on their mass, their distance from the current evaluated cell using a kernel function of a specified radius? - If I wanted to "build" a Gas Particle to Field from scratch, for example to implement the functions and methods proposed in the literature (like the ones proposed above) in which language would it be possible to do it? VEX, Python, OpenCL, C++? Any information will be really useful, thank you very much everyone.

Thank you, I watched a tutorial on how to bake the camera in Houdini, and then I used 'Scene Import (Camera)' in LOP to import it.

Houdini has sooo many cool nodes, thanks for sharing the file. I learn new things every day.