ChristopherC Posted August 17, 2015 Share Posted August 17, 2015 Hi there! I've made a simple pyro setup (see attached scene) to see if changing the scale of a pyro simulation affects its behavior and I'm quite surprised with the results. In the scene there is a “SCALE” node affecting the size of the source volumes, as well as the size and divisions of the pyro container, and the buoyancy lift value. All this to keep the values relatively the same. I probably have to scale some other forces but I'm not sure which ones and I realize that it can quickly become both cumbersome and error-prone. In any case, if the “SCALE” node is set to a value of 1 then the pyro simulation do its usual thing, but if it is set to 0.01 for example, nothing works anymore. Did I miss something obvious to get the same results at any scale? Is it considered a best/required practice to run pyro simulations at a “normal” size before scaling them up/down to what's needed? Thanks, Christopher. pyro_scale.hipnc Quote Link to comment Share on other sites More sharing options...
Farmfield Posted August 17, 2015 Share Posted August 17, 2015 Houdini units are in meters so a 2 unit high box is 2 meters high and as the DOP solvers are set to the Houdini unit scale, just keep to real measurements and you will get the correct behavior from your simulations. Now, if you don't use the correct object scale, you can compensate for that using the scale parameter in DOPs, but I would propose it's "better" (easier) keeping to correct object scale in the scene. Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted August 18, 2015 Author Share Posted August 18, 2015 I know about Houdini units being meters and keeping the correct scale of my simulations is exactly what I'd love to do—the issue being that it behaves really (really) badly when I do so in my work scene, and its noticeable also in the test scene attached. I've found that adding a few substeps in that test scene seems to help to get back an expected result but this trick doesn't seem to be enough with my work scene. I'm not even sure why substeps would be needed, espcially since it doesn't seem to be a recommended approach to simulating fluids. I'll keep investigating! Cheers! Quote Link to comment Share on other sites More sharing options...
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