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Everything posted by anbt

  1. I have selected the first points of some lines scattered around a tube like shape. I get what is on the image. I'd like to convert this into a polygon. You will tell me to just get the shape I used to scatter the line around, but to make it short, this is animated and the original tube shape doesn't move the same as the one you see in the picture (this comes out of a vellum solver) Hope I am clear. I could for example use a VDB from particles, but is there a node to just link all the points into a surface. A bit like a skin sop. Cheers
  2. @Dweeble yes indeed, just once, and potentially later again at another frame. But I have no clue if this is gonna fix my problem, this is just an idea to try
  3. I tried with a volume wrangle and multiply by -1 the name of my volume (collision), it didn't work if ($F>178) { @collision *= -1; } Any idea? Thank you
  4. Here is the full description of my issue with the hip file. I am generating a flip sim within a hollow VDB collider. That same VDB opens up at the top (ideally, I'd like the liquid to overflow from the top at some point), but for some unknown reason (possibly this VDB sign), the sim starts to get slow, and it stops filling up. https://www.sidefx.com/forum/topic/80058/?page=1#post-343937 I am baffled by this issue. And couldn't get any clue as to what's not working so far.
  5. I am silly, I have to use a volume wrangle, but in the end, it doesn't do what I expected so whatever, this is not the way
  6. Thanks for your answer, I tried but it doesn't change anything. Is my attribute wrangle placed correctly? I tried 'run over points' and primitive in the wrangle) Where can I see the sign value in the geometry spreadsheet of my static object VDB collider, so I can see if anything changes? Cheers
  7. thanks again for this @ibamobt. your 2nd method produces an interesting result but the VDB is made out of particles, so it gets full of holes as it grows! But it looks rad! In your first method, you polyfill the shape, so it's closed, and it works. I forgot to mention that instead of having a closed shape, I want to thicken it so it stays open at the top, but the VDB would work because it is extruded/thickened. I am trying to fill this shape with liquid as it grows. But I am encountering a problem at a certain frame. It stops filling and gets extremely slow. I think this is because the VDB is starting as a closed and hollow shape with the liquid generated inside, then it opens up at the top, and it starts getting weird. I have no idea how to fix this, perhaps I should invert the VDB sign at this specific frame, I don't know, it is a bit beyond me. I also have to thicken as hell my VDB collision geometry, and it doesn't match my initial geo anymore, that sucks, and couldn't find another way around this! If you have some knowledge in flip sim or anyone else can help, that would be awesome. I have attached the hip file Thanks! test_liquid_inside_vdb.hip
  8. Hi there, As you can see on the video attached, my VDB is jumping from being fine to suddenly being almost gone, and then appearing again. What could be happening? The geometry that has been turned into a VDB has a fixed number of points. It was a curve fed into a revolveSOP, curve has been resampled to a fixed number and then that curve is scaled. Thats why the number of points is not changing. I am mentioning this because maybe it matters, but it probably doesn't. I don't know! If anyone knows how to fix this, that would be awesome!!! Thanks 2021-07-08 17-06-31.mkv2021-07-08 17-06-31.mkv
  9. Oh thank you very much, I will look at this as soon as I can!
  10. @ibamobt here you go, thanks for having a look vdb_issue.hip
  11. fixed it by inadvertently adjusting the mass of these constraints points! Not sure to understand why this works because I would have thought the stiffness matters here
  12. I am really puzzled by this. It is a regular flag setup, with the top edge points attached to the collision geometry with some attach to geometry constraints. Whenever my collision geometry moves quickly, the constraints gets stretched even when I set them to be really stiff. Any idea? Thank you
  13. so now, I fixed one problem, but I get a new one in return for free I made my collision volume way thicker, which I didn't want to because I can't get a nice liquid filling closely along the inside surface but at least, it fills up the inside until a certain frame, and then, it suddenly stops. I noticed by visualising collisions in the flip object (the stuff in purple) that my collision area reverses itself at a specific time (it kind of inverts the sign of the SDF. I mean not kinda, this is what happens!) I figured out it comes from my shape which starts as a closed shape (a hollow shape but closed), and then it opens from the top. And it is at that specific moment my liquid starts to act weird. It doesn't fill, and it gets extremely slow. Any idea how to fix this? So far, I managed to fix everything but now, it starts to get too tricky and I am sure the answer will be a line of Vex to tell my volume to not inverse itself at the specific frame but I don't know how to do this. Or is it something else? Cheers!!
  14. Hello guys, I am desperate on this one! I want to fill with water this evolving shape that starts from nothing and expand like a flower. The idea is to make the fluid squirt out of it from the top (there is a hole on the top of the geo) but to start, I was thinking of filling the geo first. Maybe there are other ways to get the squirt going but I would like to fill the shape with liquid first. I am aware that I should use deforming VDB object for collision, I know the workflow but there is definitely something I don't know here. Whatever I do, the liquid goes through. I tried with a super high res VDB or even 8 substeps, nothing works. I suppose it will be easier if I attach the file so here it is test_ffluid_inside_growing_geo.hip Any idea? Thank you very much
  15. maybe I could turn those plants into a really stiff vellum and the collisions would be handled there, but with all the remeshing needed to get the geometry to work with vellum, I am not sure I would end up with a satisfying result. And it might be super slow if I instance thousands of plants!!!
  16. Hi there, I am growing and instancing a few plants on a surface. The growth animation is done at the SOP level. I am now trying to have them collide with one another. But because everything is done in SOP, I actually don't know how to tackle this issue. Any idea? Thank you
  17. thanks! ok, I understand that I was quite unclear. I animated the growth of different plants using different techniques. One is a rigged curve fed into a Revolve Sop. The animation is made of keyframes. I am also using a carve node for the stem, and I animate (with keyframes) the u and v. Basically only SOPS and keyframes. I am using some noise on the points to make them move. Then other ones are more or less done in the same way using only SOP nodes and instancing some geometries along the normals of the points of the stem. I am looking for different methods to make SOP based geo collide with each other. It might sound extremely vague, sorry for that, I don't know how to be more specific. So, the method would be to use volumes and some vex? If anyone knows some other ways, even if it doesn't apply to my issue, I'd still love to know. I am looking for directions to experiment with. Thank you very much
  18. Adjust orientation of N along curveu

    almost the same. I can't rotate the normals completely around the axis (360*), but I can achieve the same result until a certain angle of rotation
  19. Hello guys, could anyone help me achieve what I just draw? I used the OrientAlongCurve to orient my normals along my curve. Then I use the AttribRandomize with N as Direction Attribute in the parameters. So far so good, I have the drawing on the left. I would like my normals at the bottom to be closer to my curve and the ones at the end more perpendicular. What should I do? basically it is the Cone Angle parameter of the attribute randomize (set to Distribution Inside Sphere) that I would like to scale by curveu (I think this is what I have to do). But how can I fetch a parameter and use it as an attribute in a wrangle or VOP. I probably don’t have to do this for my issue but this is something I was wondering how to do. Thank you !
  20. Adjust orientation of N along curveu

    I found another way without using matrices (which seems to produce the same result, as far as I can see) by using the Attribute Transfer and the lerp() function between the two different normals: float amount = chf('amount'); @curveu *= amount; amount = chramp('ramp', @curveu); v@N = lerp(v@N, v@N2, amount);
  21. Adjust orientation of N along curveu

    wow, thank you. I am decrypting your code at the moment and trying to understand it. So far, from my understanding is that you: - create N along the curve - create another N perpendicular to the curve - create an axis from the cross product of those two different normals - create an identity matrix - rotate that identity matrix according to the position on the curve - multiply N by this new rotation Well, I think I get it, the only tricky thing is that identity matrix because I had not seen it before. Thank you very much
  22. I suppose I do this with the GroupFromAttributeBoundary sop node? I did this, it works more or less. it kind of deform a bit my geometry. Is there another way? Cheers
  23. Hello, I would like to get rid of these edges and keep the bigger rectangle. How can I do this? Thank you
  24. but it doesn't work for constraintGeometry... anyone?