Affect Volume Density by Geometry Distance

[whodini]

Would it be possible to have a sphere primitive or any geometry affect the density of a volume (fade density from 0 to 1) based on distance between the geometry's pivot (or all points) and the volume?

[lukeiamyourfather]

Long story short, yes. There many ways, some better than others. If you can explain the context it would help to make an example that would be meaningful to your workflow.

[whodini]

Thanks for replying, I just whipped up a diagram on my phone (excuse the poor handwriting) but this is what I am trying to achieve. Let A be the volume I want to affect, and let B represent an object (either geometry or volume) placed close to A. I'm trying to do something like an attribute transfer but with volume density, in this order: copy density from B to A with a given distance threshold.

Edited January 3, 2013 by rhussain

[tjeeds]

Here's a way to do it using 2 volumes. The key is to pad the volume that you want to use for falloff by the distance over which density will be affected, otherwise when you sample outside the bounding box you get a distance to the bounding box itself plus the distance to it's center (I think). Be careful plugging in large objects as the volume resolution is set to By Size in order to account for changes in padding.

Another approach might be to convert all voxels to points with a density attribute, use a Ray Sop to get the minimum distance and then sample the points back to a volume. This would save the step of converting the affecting object into an SDF and might be beneficial if you have a very large distance relative to voxel size. Might.

densityFalloffFromGeo.hip

[whodini]

thanks a lot for all the help. Your scene file was extremely useful, I like that approach a lot, it works well.

[anim]

if you want to fade just by distance to points, you can sample pointcloud from within volume vop, therefore you will avoid converting collision object to volume

volume_fade_near_points.hipnc

[tutumannyaque]

On 1/4/2013 at 9:09 PM, anim said:

if you want to fade just by distance to points, you can sample pointcloud from within volume vop, therefore you will avoid converting collision object to volume

volume_fade_near_points.hipnc

Thank you so much anim! Your technique works perfectly.

[x0z79592]

On 1/5/2013 at 10:09 AM, anim said:

if you want to fade just by distance to points, you can sample pointcloud from within volume vop, therefore you will avoid converting collision object to volume

volume_fade_near_points.hipnc

Hi, I can't find any help document about old for loop VOP. Can you kindly update your hip? Or please give me some link for tips?

[anim]

1 hour ago, x0z79592 said:

Can you kindly update your hip? Or please give me some link for tips?

wow, this is old

here is H18 version, you can directly query closest surface (minpos()) or closest point (nearpoint()) so no need for loops

volume_fade_near_points_h18.hipnc

[x0z79592]

On 5/5/2020 at 12:18 PM, anim said:

wow, this is old

here is H18 version, you can directly query closest surface (minpos()) or closest point (nearpoint()) so no need for loops

volume_fade_near_points_h18.hipnc

EDITED:wtf my comment was replaced to a porn site link by someone.

Edited July 16, 2020 by x0z79592