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AntoineSfx

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AntoineSfx last won the day on November 24 2019

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About AntoineSfx

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    Antoine L
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  1. copy to points with adjustment to size of objects

    It's trivial nowadays, thanks to Chain SOP (since 18.5) Have a look at the 18.5 presentation (H18.5 LAUNCH EVENT on Sidefx.com) Proof: books.hipnc
  2. The refraction looks right, but it looks like the object is casting a shadow as if it were opaque. Rendered with Mantra Not sure about the physics model used in Mantra though. So is it actually physically right, and if it's not, can I do something about it ? glass.hipnc
  3. What does resample / Subdivision curves converge to ?

    I may be overlooking something here. The points are in the XY plane. I'm not sure if a convert SOP using a polyline as input and its type set to NURBS curve is even supposed to converge to the same curve as the initial NURBS curve built on those same points, as there is also a knot vector associated with the sequence of points in each case. Also, it is not documented that resample / subdiv curve will actually converge to a NURBS curve, so I don't blame them. Some background here.. I'm trying to see if I can strategically place some points on a polyline so that it SOP resample / subdiv curve to a sequence of straight lines and circle arcs. Circles arcs and circles can actually be represented exactly with NURBS, so that's why I'm investigating this. If I can set the right order and knot sequence, I hope it will actually converge to circle arcs and straight lines, but I'm not there yet.. nurbs.hipnc
  4. Does SOP resample / subdivision curves converge to a specific curve ? If I use a polyline built on a NURBS control points as input, it almost converges to the original NURBS curve, except for the first and last three segments.
  5. Subdivide the result of a boolean. Issues.

    If you can't design the mesh for polybeveling that specific edge, i.e get rid of the edges between the adjacent planar primitives, then do one of those: group the ring primitives and the larger primitive together, the do a divide / uncheck convex polygons, check remove shared edges. This will be much more polybevel friendly. or: group the larger primitive, then group expand SOP it with: flood fill + restrict by normal = 0 The trick is .. polybevel can somehow slide on ring edges to hide small asymmetry problems in meshes, but it can't do magic. It doesn't somehow recursively slide on adjacent primitives until the target curvature radius is reached. So it's up to you to make sure there is no other edge too close to the edge you're trying to polybevel. At least that's how I see it.
  6. Flattening mesh with RaySOP

    No. You're assigning a point to a float. Also , promoting a 3 component vector attribute to its minimum doesn't seem like a good idea. Will it find the minimum value using a lexicographic comparison over R^3, or will it do it independently over each component ? The documentation is not clear about it
  7. Subdivide the result of a boolean. Issues.

    Also: circle --- polyextrude: Distance 0, inset some value -- polyextrude -- polybevel Set some value greater than 1 in the divisions in the polyextrude SOP so that the quads have roughly the same size. It will result in a correctly quadrangulated geometry that will be subdivided as expected, and the subdivided result will have a nice topology, which you will appreciate downstream.
  8. Procedurally Select Points on Outside Corners

    Measure SOP Parameters: Element Type:Points Measure: Curvature (Principal) Group: points with @curvature>0 Polybevel previous group Less likely to break...
  9. Flattening mesh with RaySOP

    Not sure what your problem is, but you can try setting Scale in Ray SOP to .999 to make sure the primitives from one side don't end up in the same plane (i.e. sharing the Y coordinate) as the primitives from the other side in the case you're projecting on a plane. See https://en.wikipedia.org/wiki/Z-fighting
  10. Skin SOP, shift pairing

    Actually, yes, it's possible directly. I just found this: Reverse SOP, vertex shift, U Offset Change U offset until you're satisfied with the pairing.
  11. Fuse edge to generate center line

    No. The problem is called Straight Skeleton. It is a well studied comptl geo problem. There is a robust implementation in CGAL, but it's most likely not an acceptable answer. It's a hard problem that you can't just solve with a few chained SOPs sadly. The closest you will have in Houdini is this: do a polyexpand SOP with those parameters: Output: Offset Surfaces Offset: some large number greater that the dimensions of your object. After that, finding the actual straight skeleton is not trivial either, because it is not a curve, but a tree. It does not exist as an object in Houdini. You can have a look at the vertex attribute EdgeDist, in some cases it may help to delete some points to help you build the skeleton.
  12. Skin SOP, shift pairing

    I have a curve, which I modify with edits and resamples. I later merge it with the original geometry, and skin the result. How can I shift the points in a curve to affect how Skin SOP pairs points ? I tried Sort SOP/shift but Skin SOP doesn't seem to use that information. It's using the same point order as in Carve SO, so I think it's related to how a polygon is uv parametrized internally, so I'm looking for a way to shift that..
  13. Polybevel on two merged objects . Topology Help

    Boolean SOP is too unstable to do this properly. On top of that, Polybevel is also very numerically unstable. It will try its best to slide the bevel on edges, but with an intersection of two polygonal (meaning a lot of points and straight edges), it will lead to a different result depending on the relative locations of the two intersection objects. It will break / jump as soon as there is a topology change in the result, and it will if you animate it. Also, you're using two beams of the exact same width, which leads to a bad edge case in boolean where you end up triangulating a set of coplanar points, which is guaranteed to give random results ( look at the tooltip help on Random seed in triangulate2d SOP parameter: I think it's related, not necessarily in term of internal implementation, but the general idea) Can you modify the scene so that one of the beam is larger than the other by the amount of bevel you intent to put on the seam (see abseams in Boolean SOP) If you animate it, can you retrain it so that the primitives that intersect in each input of the boolean SOP remain the same ? I know it's restrictive.. Also, see the other output groups in Boolean SOP.
  14. Polybevel, how to round to an actual circle arc ?

    Interesting. Polybevel is using a different algorithm to bevel those edges, and it results in actual circle arcs.
  15. Polybevel, how to round to an actual circle arc ?

    Indian hemp. It's a vegetable. Anyway.. The reason I need a proper circle arc is because I'm using Houdini to model pieces that will be 3d printed and need to fit another piece that is an actual circle arc of a known radius. Not sure if I want to file an RFE for this, as Polybevel is already very unstable as soon as the input is a bit complex. I guess I can build it myself for a one off shape, as I don't see an easy way to fix it in the general case, as it would require to compute the center of curvature and whatnot. So if you don't know, now you know.
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