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csp last won the day on December 23 2014

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  1. Hi, I compute the velocity on an animated point and I copy a geometry on it which inherits the velocity but of course is not correct as every point now has the exact same vector. How can I realign the existing velocity in the geometry using vex without having to recompute it? I have attached an example hip. orientvelocity.hipnc
  2. primfind in vex seems to do pretty good job but it will use the bounding box of the filter-geometry and not its actual shape.
  3. Hi there, Lets say we have a bunch of packed primitives scattered in an area on the left side and a on the right side a geometry, like frustum. I want to detect all the packed primitives that even a small portion of their bounding box is intersecting with the geometry. I have one method of doing this but its not ideal, I was wondering if anyone knows an efficient and preferably with vex way to do this. Cheers, C
  4. Combine VDB vectors

    You are right, you need some editional calculation. I measure the length of vector for each merged vowel and if its higher than 0 then it will be part of the average computation.
  5. Combine VDB vectors

    That also will not give accurate velocity as not all combined vdbs contributed to every voxel. By using the volumesamplev in a volume wrangler you can get better results.
  6. Combine VDB vectors

    You gave me a wonderful idea. With a vdbCombine Activity Union I create the combine vdb and with a single volume ranger I loop through all the merged velocities fields in the second input and I store in a array the vector for each field. Finally at the end I do an avg(array) and works!
  7. Combine VDB vectors

    That's also not a average, the last combined field will override the previous.
  8. Combine VDB vectors

    Yes it can but then you are limited to 4 inputs.
  9. Combine VDB vectors

    Hi, I was wondering if anyone knows any method to combine velocity vectors of x number of VDBs with an average operation. With VDBCombine SOP either Add or Maximum operation will not give me the correct result because the add will put one vector on top of the other and the maximum will just keep the vector with the greater length. I can produce average using a volume wrangler and the avg() vex function but then I am limited to 4 volumes. cheers, C
  10. RGB to Kelvin

    Hi, I would like to convert an rgb color value of an attribute at points to temperature (kelvin). I am wondering if anyone is aware of any algorithm related to that. cheers, C
  11. Procedural (non sim) cloth creases

    It's a mistary, almost everytime I post a question few minutes later I will find the answer my self. ToPolar node will do most of the job. Still need more work for secondary creases. If you have any ideas or knowlenge to improve this setup please share it here.
  12. Hi, I am wondering if there is any noise setup in vex to create radial creases/wrinkles on a grid? Like on image from 3dsmask but on flat, ingore the bump.
  13. mask surface tension

    Can we take it one step further? How to apply surface tension only to points with velocity greater than a given threshold?
  14. mask surface tension

    Thanks David, this what exactly I was trying to do with the masking method but instead of gasparticletosdf I used gasparticletofield as I described above. Thanks again. It would be nice if surface tension was like viscosity or density which can be attribute driven.
  15. mask surface tension

    Hi, I have two sources in a flip solver and I want to have different surface tension to each one of those sources, how that's possible? In general how the group parameter in a gas microsolvers as surface tension can be used in order to effect part of a flip silumation? Or is there any way to mask it? I tried unsuccessfully to create a new scalar field matched to surface and use it as mask using gasparticletofield which was reading particle custom attribute where points of one source had value of 1 and the other of 0. Then I replaced Surface Field parameter in Gas Surface Tension with that mask filed, but as I said it didn't worked. regards, Christos