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j00ey last won the day on August 23 2015

j00ey had the most liked content!

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  1. I've just been working on an exporter to write out geometry descriptions and animation data for a realtime renderer and found it was quite manageable using python, the thing that can get tricky to get right is the formatting - square brackets, curly brackets, commas etc. This site might come in very handy for checking your output : jsonlint.com
  2. Sorry, I hadn't noticed before but I think you just need to turn on 'Initialise Simulation Ops' on the Geometry ROP. I just tested it and it came out as expected.
  3. I can't see anything set wrongly in your wedge ROP. Did you try turning off caching on your DOP network then running the wedge?
  4. I don't have that particular file to hand any more but I made you a file to demonstrate an easier method. If you take the dot product of the normalized vector P0->P1 in the drawing above, and the UNnormalized vector P0->P2 that will give you the magnitude of the vector in the (normalized) direction P0->P1 that the perpendicular projection point is. That's probably a bit garbled but if you look at the file I hope it will make sense... projection.hip
  5. Disable when doesn't work for handles it seems - unless my . I'm not talking about parameters, I want to hide a handle.
  6. I'm making an HDA and I need to have a couple of different modes, each of which need a translation control. I don't really want to have more than one visible at any one time to avoid confusion and all my UI hides and unhides itself according to what mode the user selects but I can't figure out how I can hide handles. The documentation is a bit sparse - i suspect it might be something to do with the ''onoff'' field but the ''disable when'' syntax doesn't seem to work... Does anyone know more how they work? Thanks for reading
  7. I figured it out, I had a plus instead of a minus...
  8. I'm having a little difficulty with some matrix maths. I have 3 points P0, P1 and P2 [as in the attached drawing] and I need to find the point on the line between p0 and p1, such that the line from it to P2 is perpendicular to it. The way I tried is to first find the angle between P0-->P1 and P0-->P2 [acos of the dot product], then from there find the lengths a, o and a using trig, from there it's simple to find the correct position but somewhere or other I'm going wrong. I'll persevere but I wondered if there is some standard function to find that position, I imagine it must be a common thing to want to do... Thanks in advance
  9. In case anyone else comes up against this problem, I found a workaround - go inside the sky SOP asset and copy and paste the contents of the CVEX shader builder inside shopnet/sky into a new volume VOP, then copy the parameters across. A bit of a hack but it's writing out properly now at least..
  10. Hi I've been banging my head on a wall trying to wedge a load of sections of a cloudscape and figured out that something inside the sky SOP seems to be causing the problem. If I make a standard VDB from poly andf write it to disc, it's fine but whenever I try and write a density VDB created by the sky SOP it comes out at 1Kb. IS it something to do with the CVEX shader inside it? I've tried using my standard VDB and using volumesample to get the density value from the sky but that also writes as a 1Kb file. Attached is a mockup file to make things clearer. Thanks in advance for any ideas... skybox_clouds_ODFORCE.hip
  11. Thanks very much Pavel - that looks like something to learn a few things from!
  12. Ok that's interesting, I'm not familiar with the composite CHOP, I'll have a look and see if I can switch to that and see what happens. Thanks Jon, much appreciated
  13. Hi Jon Thanks very much, I really appreciate your help. I do understand the slerping between two states, what I'm stuck with is slerping between A and B and then between B and C. I've made a file that's more or less the same setup as I have at work - it's not exhibiting quite the same flipping as that one as the work file has many more pieces that move back and forth along one vector with their normals pointing along it in opposite directions but it does have the same issue. I'm still something of a CHOPs novice so that part might be a bit inelegant but it does essentially what I'm trying to do except for the flipping. I make the target states in SOPs then interpolate between them in CHOPs and fetch the P and N values from there. So to do the quaternion VEX method I'd have to do it somehow inside a solver I think. I'm probably missing something simple but I'm not sure what... odforce_flipping_geo_orient_sequenced.hipnc
  14. Hi Jon Thanks for replying. That's exactly what I was trying to do yes but I'm struggling to get it to work. I have a point cloud which has a number of target states - other point clouds - which I'm fetching the position / normal and scale from and then I'm sequencing them in CHOPs so I can control the timing and animation between states and so on. So the problem arises when a point does what's happening in the scene file I uploaded - moves from one position to another and the normal flips 180 degrees. I could instead of getting the normal from CHOPs I could get a slerp bias but I don't understand how to get that working in conjunction with the wrangle method you're talking about. The bias would either go up from 0 to 1 and then from 1 to 2 etc or else I'd reset it so it goes from 0 to 1 and then back again. I can imagine getting that to work in a solver somehow but I thought there must be a CHOPs method. I imagine that probably all sounds a bit garbled. I can't put up an actual scene file but if I get chance I'll make a dummy version and upload it. Thanks for reading anyway
  15. I'm having difficulty with flipping normals when copying geometry onto points. I have a scene with a number of randomly generated structures, just points [each has the same number of points] and I have a CHOP setup to interpolate between them - basically a glorified blendshape - and after the interpolation I'm copying geometry on to them. The problem is that if I use the normal to orient the copies, it sometimes flips, as in the attached scene. I thought if I brought that into CHOPs and added a quaternion attrib with the attribute CHOP it might fix that problem but it doesn't seem to make any difference. Does anyone know a good way to approach this? odforce_flipping_geo.hip