Fine control VEX modelling of Voxels with VDB Wrangle

[Trilec]

Hi Superior brains,

as I approach modelling methodologies, I've turn my attention towards VDB's

In the below example I've used a grid (but this would be an arbitrary shape Convex/concave "2Shape") with a noise pattern to create heights for a later extrude; I then convert to VDB to "cleanup the geo"

My question: is it possible to directly manipulate the VDB via VEX to do something similar without having to go through the conversion process (poly to VDB)

One reason behind this is the shape I wish to extrude can be fairly complex and dense thus making the conversion process slow, so perhaps adding voxels or extruding/expanding/manipulating voxels is possible in some way? ( VDB Wrangle?), feels like this is not possible but never hurts to ask... unless its physical...;)

 

[Librarian]

maybe It Helps
Nice examples with Files.
http://wordpress.discretization.de/houdini/
 

[Trilec]

Thanks Tesan,

Seems the Volume Wrangle geometry node might be worth exploring, ideally I'm trying to avoid advanced mathematics but certainly there might be some tricks here that are interesting. I will need to find some some simple examples using this node to get a better understanding. I assume this means there's no direct manipulation of voxels as in VDB only volume voxels.. or are these the same?

thanks again.

 

 

Edited July 4, 2020 by Trilec

[Librarian]

@Trilec
here it's maybe
Iso math some examples( scroll to find)file

https://forums.odforce.net/topic/44999-on-growth-and-form/?page=4

 

[konstantin magnus]

Hi Curt,

to shape a skyline you could write something like this into a volume wrangle:

vector pos = set(v@P.x, 0.0, v@P.z);
float dens = rand(floor(pos * 9.99));

f@density = v@P.y < dens;

 

voxel_buildings.hipnc

[Trilec]

thanks Konstantin ,

A nice simple example, It seems attribute transfer is problematic  for volumes.

I and trying to roll off at the edge and approched this with getOutsideGroups ...attribtransfer and attribpromote

Is there a good way to get the same or similar with voxels (volumes) (soft rolling off to the lower edge)?

thanks again

 

[konstantin magnus]

A signed distance field already is a volume that 'fades out' towards its borders. So as soon as you go VDB-from-volumes and use 'distance VDB' you should get what you want.

Or are you attempting to measure the distance from a voxel to an outline curve or anything?

[Trilec]

Thanks,

After further investigation, seems harder to control VDB than through pure poly mesh (for something like this)

I was trying for an even roll as the shapes are arbitrary from bottom to top.

Seems you can pass attributes via vdbfrompolygons , but not sure if this is the best solution as the vdb resolution with get very high.

using

vector rbox = relbbox( @P );

//boost the lower portion
if(rbox.y < 0.06) density = 1;

//shape
f@density  -= rbox.y *.2; 

 

In the wrangle I get a little way but it  removes the top and bottom and falloff not quite there yet.

 

Edited July 10, 2020 by Trilec
added code