SDF Blending

[GallenWolf]

Levelsets In Production: Spider Man 3 / SDF Blending
http://www.jcohen.na...elsets_2007.pdf

I've been passing this hip file around, so thought I'd just put it up in the forums

GW

sdfBlending.hipnc

[J.Santos]

That looks really cool!

Thanks for the file!!!

[anim]

hey Alvin, nice example, I hope you are doing well in Montreal

[GallenWolf]

I'm doing ok, thanks for asking

[hanton]

Amazing work!

[Pazuzu]

Thank you very much for sharing this!!!

[pcbiajante]

Great work! Thank you very much for sharing!

[Hudson]

Very nice and thank you for sharing this Alvin!

[j00ey]

Yes this is very interesting, thanks for sharing.

I'm trying to do something similar but with some very large, detailed models so I had been using VDBs and doing a pretty simple merge. So I tried recreating this 2 box setup with them but I can't get it to work. I'm pretty new to Houdini so maybe I'm missing something really simple.

Does the Volume VOP not support VDB for instance?

Thanks again

[edward]

The Volume VOP supports VDBs, however it will only operate on the active voxels.

[j00ey]

Hi Edward

Thanks for replying. I realised eventually that that was what was going on. I was using a VDB Activate SOP with the second box geometry plugged but had misunderstood what it actually did. So I've been thinking how I can activate just the voxels in the area of the fillet without using a volume to determine that area. I think for now it's beyond me.

Thanks again anyway

[kgoossens]

Thanks for the example file Alvin!

[Mzigaib]

Awesome! Very useful thanks for sharing dude! 

[Mzigaib]

Hi Edward

Thanks for replying. I realised eventually that that was what was going on. I was using a VDB Activate SOP with the second box geometry plugged but had misunderstood what it actually did. So I've been thinking how I can activate just the voxels in the area of the fillet without using a volume to determine that area. I think for now it's beyond me.

Thanks again anyway

Any updates on that?

[Falcon]

Thanks a lot! Very nice example

[kurtw]

Does the Volume VOP not support VDB for instance?

 

Actually the supplied VOP will work with VDB's but VDB's handles it's data a bit differently, where the range where it will work is .. very small depending on you scale & grid resolution.

 

The solution is to ensure you have enough "working space" around the VDB surface by adding enough padding around it. To do this during the VDB from polygons step, make sure you raise the Exterior Band Voxels so it encompasses the areas where you wish to blend/fillet the vdb's together.

 

The default of 3 won't work, so I found values of 20-100 would work, it will slow things down since you are creating a larger "band" of active voxels around each of your inputs, but it'll still be an order of magnitude faster and more precise than using iso offset.

 

So for very irregular shapes, you'll want to put down an Open VDB Visualize or VDB visualize tree and look at the active voxels of both inputs to make sure the working active voxel radius will give you enough working area for the surface blending.

 

One thing I've tried and I've seen others tried is to manually [as a post process to the vdb surface generation] enlarge the active VDB grid, either by combining the two input grids into one via a volume mix, or using vdb resample/reshape to make a bigger grid, but that doesn't seem to work with the volume vop as presented, a step is missing that is applied during the active voxel generation of the initial surface creation.

 

Either way, adding enough active voxel padding will work.