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  1. I'm doing some research on 4D -> 3D projections and looking to create some 4D geometry in Houdini. I've seen an equation to do it here but could use some help converting this to VEX: https://hollasch.github.io/ray4/Four-Space_Visualization_of_4D_Objects.html#s4.3
  2. Pop Grains Friction Problem

    Thanks Henry, Clumping stiffness lowered to 20 seems a bit more stable. It's a little more slumpy than I'd like but it might work. In regards to the weights all adding up and == 1, its interesting... I can have a weight of 0.9 internal collision + 1.0 clumping = 1.9 and it seems to resolve more "stable". I could lower each one to 0.5 and 0.5 which would be technically more "correct mathematically" however then the clusters then really slump a lot. I guess its a balance of cheating physics until it becomes unstable, and we are allowed to do that with these controls but you never know when you might pass over that threshold and get a weird result!! I might look into explicit constraint for the grains to hold them together in clusters... I've never used them much but I imagine it works kind of like a glue constraint in an RBD simulation? but then explicit constraints also have a weight and stiffness so I'm kind of curious what's the benefit of using "clumping" over "constraints" they seem to be able to do the same thing in just a slightly different way?
  3. Pop Grains Friction Problem

    I have a grain setup with clusters using attraction weight. The particles with no cluster attraction weight come to rest nicely but the clumps of clustered particles look like they are on ice and skid along as if they had no friction. I tired increasing the scale kinetic value and although that does hold the big chunks with more added friction it really makes all the small individual particles come to rest way too fast and feel sticky. Any idea what the parameter is that I might use to get those bigger clusters to come to rest with friction a bit better while maintaining just a little bit of skid overall. popGrainIceSkate.hipnc
  4. shader noise on rest fields

    adding onto this topic, I am trying to do something similar, use a dual rest pos in a "Billowy" shader which is by default only setup for a single rest position. I wonder if its possible to copy an d paste the dual rest structure from the pyro into billowy? I see that the output of the dualrestsolver is of type "struct" however what I need is a type Vec3 postion to enter into the billowy noise position. Is there a way to convert this dual rest so that the output can drive the noise position properly?
  5. Constraint group broken

    Ahhhhhh ok great. makes a little more sense. This was an example network I was examining, not one of my own design. I'm using it for learning purposes Typically I would build it a little different instead of animating the @strength value in SOP land, I would put in a static attribute such as break frame where the constraint could be set in conditional statement in a sop solver within the DOP network to break at a predefined time. That might lead to more consistent/stable solving of results per frame. Now it makes sense why the constraints were re-making themselves because they were being brought in fresh every frame with the overwrite with SOP! this is great to know, thanks for the help.
  6. Constraint group broken

    Well well well would you look at that, the shelf tool does indeed create a delete node in a sop solver to remove constraint prims. I myself don't use the shelf tools and I would have to say about 99.9% of the tutorials about glue constraints also omit this sop solver step which removes the prim. It does seem that sideFX has enabled the breaking constraint without it, which makes me wonder if sop solver to force remove prims is now redundant? So I tried to add the delete prim into the sop solver network to make this particular example of constraints more stable and still getting blinking constraints on and off and on again. can't really explain it. maybe its somehow caught between a pre and a post solve state? Dop_glue_v01.hipnc
  7. Constraint group broken

    yes its not a problem per say, I'm just curious about the expected behavior. I always thought once broken a constraint was broke it was always broke... so this would fundamentally change how I need to think about how the solver behaves.
  8. Constraint group broken

    I've been messing around with constraints lately and I stumbled on an example where a glue constraint primitive would break, then unbreak, and break again. That is to say the impact value on a given frame was above the strength of the bond and so it added itself as "1" to the @group_broken then on subsequent frames it un broke giving the @group_broken a value of "0". Am I crazy or is that expected behavior? I thought once a glue constraint was broken it was forever broken?
  9. UV unwrap without holes

    Still looking into this to see if there might be a better way. I can potentially UV the voronoi clean at low res, and then apply the remesh after the UV but remesh kind of destroys the UV. Is there a way to preserve the UV's through the "remesh" operation?
  10. UV unwrap without holes

    Trying to use the uv unwrap on some high res geo but it produces holes in the planar projections (as expected but not desired). some of my texture baking operations in other applications are creating some artifacts because of the non seamless UV surfaces. Is there a way to weld them back together to make more seamless uv shell islands? Or to somehow make a "shell" attribute from a low res geo that could then stick to the high res remesh? UV_textureing_question.hipnc
  11. Particle collision Physics with RBD

    I'm trying to get good physical interaction between a baked RBD geo and a particle system and the particles seem like they are either all stuck or all slide with nothing in between? I'm bringing in the RBD as a static object collider, with deforming geometry turn on, and set the collisions to Use Surface Collisions (the green guide one). The particles collide but for the most part they stick really harshly even when friction is turned down all the way. If I go onto the pop solver and in the collision behaviour tab, set the response to slide.. they slide but then it looks like its on ice and the friction controls are disabled. Any ideas how to get a good setup? I'm trying to make something like rock debris on a cracking ground surface. so there should be some tumble and roll but eventually come to a stop, maybe a slight bit of bounce but not really too "bouncy" either.
  12. Debris source

    yea i noticed you could dive into it but wasn't sure the "standard" way to make an id... looks like in this case its just ptnum. In the case of the debris asset, I was worried about using id=point number because it seemed to adding, removing and changing point numbers on the output and creating an id based on that might lead to bad or inconsistent results. Now I see that you added the ID before the point culling "visualization" wrangle happens which makes it work. Now I also know how to also add in a rest position! It looks like this mysterious asset at its heart is a fancy scatter points. Cool!
  13. Instance Packed objects

    I'd love to have a way to keep it as a live network and reference a packed object in an op:string. I'm on a really complicated network where the path variables are out of my control and produce very complicated string paths if I write out files.
  14. Instance Packed objects

    I'm trying to create a voronoii fractured geo to make rocks that will instance onto scatter points. when I pack the object it will make a path attribute for each chunk something like this: op:/obj/debris/assemble1/pack/piece0 op:/obj/debris/assemble1/pack/piece1 etc. Is there a way to read those objects back in on an Instance SOP using scattered points on a grid? I have tried using a point wrangle to create the s@instancepath attribute variable... but I'm not able to get it to work right.
  15. Debris source

    Can you get unique point id's from the "debrissource" SOP tool? I need this because the "scatter points" have an age and so they die which tosses ptnum out the window for instancing. It seems like ID would be a built in option for this sort of thing?