melazoma Posted July 17, 2009 Share Posted July 17, 2009 Hi all, This is more of a SOPs question than DOPs. I'm looking for a way to re-time the PyroFX volume primitive cache. Timeblend + Timewarp will work for deforming polys, but not for volumes. Does anyone have a solution to timeblend/interpolate the subframes of a deforming volume? Thanks. Quote Link to comment Share on other sites More sharing options...
Macha Posted July 17, 2009 Share Posted July 17, 2009 Would a timeshift and volumemix SOP do the job? Quote Link to comment Share on other sites More sharing options...
pclaes Posted July 17, 2009 Share Posted July 17, 2009 Have a look at that other thread where you go from particle to volume. You do the reverse by defining your grid with the same resolution as your voxels and then read the attributes in vops with gradient/sample from file. Once you have the attributes in place, do the usual blendshape based interpolation timewarping. Then transfer back to volumes. - not sure how many detail you will lose through conversion. Probably a direct volume interpolation in vops is the best solution, so yeah scrap the first suggestion . Quote Link to comment Share on other sites More sharing options...
melazoma Posted July 17, 2009 Author Share Posted July 17, 2009 Have a look at that other thread where you go from particle to volume. You do the reverse by defining your grid with the same resolution as your voxels and then read the attributes in vops with gradient/sample from file. Once you have the attributes in place, do the usual blendshape based interpolation timewarping. Then transfer back to volumes. - not sure how many detail you will lose through conversion. Probably a direct volume interpolation in vops is the best solution, so yeah scrap the first suggestion . Thanks for the tips, pclaes. "direct volume interpolation" May I ask how would one approach this? Is it as simple as grabbing the V voxel value from the previous and the next cached frame and interpolate between? Not that I have any idea which volume VOPs to use... But it couldn't hurt to ask. Quote Link to comment Share on other sites More sharing options...
anim Posted July 17, 2009 Share Posted July 17, 2009 ...May I ask how would one approach this? Is it as simple as grabbing the V voxel value from the previous and the next cached frame and interpolate between? Not that I have any idea which volume VOPs to use ... Macha just told you: timeshift and volumemix SOP the workflow is exactly the same as in TimeBlend(dive inside) just replace blendshapes with volumemix SOP (set to blend) just be aware of that pyro has more volume primitives so you have to blend all of them (inside foreach sop) Quote Link to comment Share on other sites More sharing options...
essencevfx Posted August 12, 2009 Share Posted August 12, 2009 how would you go about blending the volumes, I'm running into a problem using volume mix SOP to subtract sections of my pyro fields post sim. I assume this is why a single volume mix subtract doesn't remove all of the volume I'd expect it too. Quote Link to comment Share on other sites More sharing options...
pclaes Posted August 13, 2009 Share Posted August 13, 2009 how would you go about blending the volumes, I'm running into a problem using volume mix SOP to subtract sections of my pyro fields post sim. I assume this is why a single volume mix subtract doesn't remove all of the volume I'd expect it too. At the heart of the blending lies (linear) interpolation between the current and the next frame. Based upon this formula: (1-t)*V1 + t*V2 where V1 is your first volume, V2 your second volume and t a parameter between 0 and 1. Have a look at this file. I did not use vops, which would probably speed it up, but this way with expressions is probably more understandable. With vops you will most likely have to reference the volume with a gradient or vector from file as it only takes in a single input. The linear interpolation can be used everywhere where the point number or resolution does not change - that is why it will work fine for volumes or non-changing topologies. A bit trickier with particles - but you can check this other thread on that topic: Hope it helps. matrix_cheese_01.hipnc 2 Quote Link to comment Share on other sites More sharing options...
essencevfx Posted August 13, 2009 Share Posted August 13, 2009 (edited) cool thanks Ill give it a look. I made a quick hack that runs the volume through a series of blast/primitive/volumemix per prim , removes my volume, and then re-merges everything together....seems to work but quite a mess Cheers ! edit; oh i see this is an example for re-timing fluids, Nice ! , kinda makes my response make no sense though as I was chatting 'bout volume subtraction post sim blah...sorry Edited August 13, 2009 by essencevfx Quote Link to comment Share on other sites More sharing options...
johner Posted August 14, 2009 Share Posted August 14, 2009 Have a look at this file. I did not use vops, which would probably speed it up, but this way with expressions is probably more understandable. Nice one, Peter. And the cheesier the better. Quote Link to comment Share on other sites More sharing options...
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