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monomind

17.5 - Vdb To Spheres - Different than before?

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Looks like VDB to spheres is working a bit different for me in V 17.5

The created spheres used to stay within the volume before but now it looks like some of them are exceeding the boundaries of the vdb.

I've tried opening older files, they also work differently.

Can anyone confirm this behavior, or if this is intentional or not?

Not sure if a bug is going on on my end.

 

V17.5.391

 

houdini_2019-10-14_13-03-20.png

Edited by monomind

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More obvious to see for a torus instead of a cube.

I'm pretty sure this was not the behavior before.

houdini_2019-10-14_13-18-09.png

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Same here in Houdini 17.5.293. I created the scene also from scratch and I get the same result, so it's not related just to your hip. 

Changing a little the parameters or decreasing the VDB resolution, helps. But seems random, I haven't noticed any correlation

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Created spheres used to stay in boundaries of the parent object before.

I sadly don't have an older version of Houdini installed at the moment but maybe later today I can install and check - or maybe someone can do the same in an older version and check.

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For sure this was also happening in Houdini 17 because of this I had to correct with a wrangle the pscale of the spheres after "VDB to spheres"

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How exactly do you correct it? 

If pscales are modified than the spheres don't fit any more. 

Edited by monomind

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For each sphere I was looking at the distance to the surface of the geometry. If the pscale was bigger than the distance to the surface, then I set pscale to be this distance. Of course later I had to instance back again spheres to these points.

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Hm but then the distances between those resales points and everything else would fail (too much gap) - wouldn't make perfect fit any more am I wrong 

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Doing what I mentioned before gives you a good collision geometry without extra stuff but of course the spheres are not perfectly close one to the other. I have always used this for getting correct collisions and ti was enough. To be honest I don't know if the spheres have ever been perfectly packed with no gaps

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As I have my old version always installed I test it.
The most notable difference is on the large spheres.

As on the old version the parameters are always activated I set it to have the same result as yours.

Top to bottom H15, H16, H17 or 175

H15.JPG

H16b.JPG

H175b.JPG

Capture.JPG

Edited by flcc

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just tried it in 17.5.173, default sized torus:

vdbfrompolygons voxel size 0.1 works just fine but as soon as i lower it some spheres are not contained in the torus' shape anymore

When I scale the torus up and leave the voxel size lower than 0.1 at some point it works again. Seems to be some sort of correlation/ratio that makes or breaks it :huh:

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@3dome yes, seems very random.

What's more interesting to me is that it's not fixed since 17

Edited by monomind

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This is an issue with the OpenVDB code being updated to 5.0, when I asked SideFX about it a while back they said they have let the OpenVDB team know about this issue.

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