Houdini learning

Houdini learning

Increase Volume Density

// In a volumewrangle

@density *= 10;

Substract any VDB by another VDB

// In a volumewrangle

if (volumesample(1,"surface",@P)<0)@density=0;

//inverse:

if (volumesample(1,"surface",@P)>0)@density=0;

Get bound & centroid

// In a null object

bbox(opinputpath('.',0),D_XSIZE)
bbox(opinputpath('.',0),D_YSIZE)
bbox(opinputpath('.',0),D_ZSIZE)

centroid(opinputpath('.',0),D_X)
centroid(opinputpath('.',0),D_Y)
centroid(opinputpath('.',0),D_Z)

UVs

// In this order : uvautoseam - uvflatten - uvlayout
In uvflatten : Seams = seams

Attribwrangle - if...

// Kill emission on a smoke source after frame 300
if (@Frame>300) @density = 0;

Attribfrommap - Use UDIMs images

// Replace 1001 by <UDIM> and check UDIM Filename Expansion

Attribwrangle - Udim number on primitives attributes

// In a wrangle set on Primitives
vector uv = primuv(0, "uv", @primnum, set(0.5, 0.5, 0));
i@udim = 1001 + int(uv.x) + int(uv.y)*10;

Place at World center, scale et re-transform for export

// In a transform translates
-centroid(0,0) -centroid(0,1) -centroid(0,2)
// In a transform Uniform scale
(bbox("/obj/neigeSol/timeshift1/", D_ZSIZE))/(bbox("/obj/neigeSol/transform_centerWorld/", D_ZSIZE))

// At end, in a transform Uniform scale
1/((bbox("/obj/neigeSol/timeshift1/", D_ZSIZE))/(bbox("/obj/neigeSol/transform_centerWorld/", D_ZSIZE)))

Misc Attr Wrangle expressions

// Delete by color
if (@Cd.x<chf("seuilColor"))removepoint(0,@ptnum);

// Set random pscale
@pscale = fit01(pow(rand(@ptnum), ch("power")), ch("pscale_min"), ch("pscale_max"));

// Udim attr for each Udim
vector uv = primuv(0, "uv", @primnum, set(0.5, 0.5, 0));
i@udim = 1001 + int(uv.x) + int(uv.y)*10;

// Set pscale Min/Max
@pscale = fit01(pow(rand(@ptnum), ch("power")), ch("pscale_min"), ch("pscale_max"));