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j00ey

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About j00ey

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  • Name Tim
  • Location London

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  1. I figured it out, I had a plus instead of a minus...
  2. 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
  3. 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..
  4. 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
  5. Thanks very much Pavel - that looks like something to learn a few things from!
  6. 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
  7. 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
  8. 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
  9. 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
  10. Thanks both, I will look into those. At first glance the detail intrinsic approach looks good, though I'm sure I'll learn something from the other link too.
  11. I'm having difficulty with some regular expressions. I have some geometry which contains a load of groups called cluster_0, cluster_1, cluster_2 etc. The number of groups will vary and I need to be able to affect them in batches. Essentially every 5th group needs to have one set of transforms applied, so I need to do some sort of modulus in the group field. I tried cluster_[0-999:5] , cluster_[1-999:5] etc but that only gets cluster_0, cluster_1, cluster_2, cluster_3 and cluster_4 Can anyone give me a pointer? Thanks for reading
  12. No problem. I think we've all been in that situation some time!
  13. Try this, there are a couple of options for the normal orientation in there. **edit I added backface culling quick outline5_VEX01.hiplc
  14. Isn't that what space + z does?
  15. I see, but I'm only getting 4 digits in my arrays. You can see in the jpg attachment on the original post. It's actually fine for my purposes, I was just curious as to why it happened. Thanks for the info.