Difference between revisions of "Houdini learning"

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=Houdini learning=
 
=Houdini learning=
 +
=== Center Pivot ===
 +
<pre>
 +
// In Pivot Translate in a Transform node
 +
 +
centroid(0,0)
 +
centroid(0,1)
 +
centroid(0,2)
 +
 +
</pre>
 +
 +
=== Delete by Connectivity attribute ===
 +
<pre>
 +
// In a Delete node, in Group (by example)
 +
 +
@class=7777
 +
 +
</pre>
 +
 
=== Increase Volume Density ===
 
=== Increase Volume Density ===
 
<pre>
 
<pre>
 
// In a volumewrangle
 
// In a volumewrangle
  
−
@density*=10;
+
@density *= 10;
  
 
</pre>
 
</pre>
Line 18: Line 36:
 
if (volumesample(1,"surface",@P)>0)@density=0;
 
if (volumesample(1,"surface",@P)>0)@density=0;
  
 +
</pre>
 +
 +
=== Get bound & centroid ===
 +
<pre>
 +
// 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)
 +
 +
</pre>
 +
 +
=== UVs ===
 +
<pre>
 +
// In this order : uvautoseam - uvflatten - uvlayout
 +
In uvflatten : Seams = seams
 +
</pre>
 +
 +
=== Kill emission on a smoke source after frame 300 ===
 +
<pre>
 +
if (@Frame>300) @density = 0;
 +
</pre>
 +
 +
=== Attribfrommap - Use UDIMs images ===
 +
<pre>
 +
// Replace 1001 by <UDIM> and check UDIM Filename Expansion
 +
</pre>
 +
 +
=== Attribwrangle - Udim number on primitives attributes ===
 +
<pre>
 +
// 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;
 +
</pre>
 +
 +
=== Place at World center, scale et re-transform for export ===
 +
<pre>
 +
// 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)))
 +
</pre>
 +
 +
=== Misc Attr Wrangle expressions ===
 +
<pre>
 +
// 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;
 +
// Next, with a Delete SOP: Group: @udim=$F - Pattern mode !*
 +
 +
// Set pscale Min/Max
 +
@pscale = fit01(pow(rand(@ptnum), ch("power")), ch("pscale_min"), ch("pscale_max"));
 +
 +
// Remove small parts - In a Foreach connected piece loop
 +
@size = (getbbox_size(0).x+getbbox_size(0).y+getbbox_size(0).z);
 +
 +
if(@size < chf("taille"))
 +
removepoint(geoself(), @ptnum);
 +
 +
// Set @variant integer for Copytopoints (change objects number)
 +
i@variant =floor(rand(@id)*3);
 +
 +
//// Get position difference between two objects, and match animation
 +
// On Rest pose object:
 +
v@fixe = 0;
 +
@fixe.x = getbbox_center(0).x;
 +
@fixe.y = getbbox_center(0).y;
 +
@fixe.z = getbbox_center(0).z;
 +
// On animated object:
 +
v@anim = 0;
 +
@anim.x = getbbox_center(0).x;
 +
@anim.y = getbbox_center(0).y;
 +
@anim.z = getbbox_center(0).z;
 +
// After two previous AttrWrangles:
 +
v@anim_offset = point(0, 'fixe', 1) - point(1, 'anim', 1);
 +
// To match animation:
 +
@P = point(0, "P", @ptnum) + point(1, 'anim_offset', 1);
 +
 +
//// Blend shape through a mask attribute - Posted by Cudarsjanis on Odforce
 +
// Geo with mask attribute in first input, blend shape in second
 +
v@P=lerp(v@P, point(1,'P',@ptnum), f@mask*ch('blend'));
 +
 +
//// Set a fixed normal attribute
 +
v@z = set(0,1,0);
 +
 +
//// Place at world center
 +
v@P -= getbbox_center(0);
 +
</pre>
 +
 +
=== Delete small pieces ===
 +
<pre>
 +
// As seen on Sidefx forum, posted by paulboiii
 +
// First create a measure SOP, set to per piece
 +
 +
// Then, in an attribwrangle set on primitives
 +
float threshold = chf("Size_Threshold");
 +
if ( f@area < threshold ) removeprim(0,@primnum,1);
 +
</pre>
 +
 +
=== Attribute Wrangle - Copy attribute from second input ===
 +
<pre>
 +
// With same number of points on both inputs - From Bonsak on Sidefx.com
 +
 +
// Copy P from second input
 +
@P = v@opinput1_P;
 +
</pre>
 +
 +
=== Bounding-box - Position Reference color ===
 +
<pre>
 +
// As seen on https://houdinihelp.ru/ref/expression_cookbook.html
 +
 +
// In an attribwrangle set on primitives
 +
@Cd.r = relbbox(0,@P).x;
 +
@Cd.g = relbbox(0,@P).y;
 +
@Cd.b = relbbox(0,@P).z;
 +
</pre>
 +
 +
=== Group by uv.y ===
 +
<pre>
 +
// Thanks to https://vfxbrain.wordpress.com/2019/06/14/vex-snippets-2/
 +
 +
// In an attribwrangle set on points
 +
if(@uv.y<chf("seuil")) @group_base = 1;
 +
 +
// ALTERNATIVE
 +
@uv.x<0.2
 +
</pre>
 +
 +
=== Specify attribute value for one point ===
 +
<pre>
 +
if (@ptnum == 322) f@mask=1;
 +
</pre>
 +
 +
=== Pscale by Bbox Y ===
 +
<pre>
 +
//set pscale first
 +
 +
f@bboxY = relbbox(0,@P).y;
 +
@pscale *= chramp("rampBbox",@bboxY)*4 ;
 +
</pre>
 +
 +
=== Delete primitives by height ===
 +
<pre>
 +
if ( @P.y<chf("seuil") ) removeprim(0,@primnum,1);
 +
</pre>
 +
 +
=== Falloff geometry ===
 +
<pre>
 +
// Get camOrigin
 +
 +
vector pt0 = point(1,'P',0);
 +
v@raydir = normalize(  pt0 - @P )*-1;
 +
 +
@falloff = dot(v@raydir, @N);
 +
 +
// Promote raydir in Primitives
 +
 +
if ( f@falloff>chf("seuil") ) removeprim(0,@primnum,1);
 +
</pre>
 +
 +
=== Labs Maps Baker - Bake with UDIMs ===
 +
<pre>
 +
// Add %(UDIM)d in the file path - don't need to check Output UDIMs
 +
</pre>
 +
 +
=== Gets the digits from node name===
 +
<pre>
 +
// Add `padzero(3,opdigits("."))`
 +
// Add `padzero(3,opdigits(".."))` for previous node padding
 +
// padzero(3,opdigits(".")) without hscript
 +
</pre>
 +
 +
=== Self-shadows in Mantra===
 +
<pre>
 +
// Add by example * ^RENDER_ground in Shadow Mask of every of your lights to exclude self-shadows
 +
</pre>
 +
 +
=== Search and replace in VEX ===
 +
<pre>
 +
// To remove ShapeDeformed from Maya Alembics by example, in an Attribute Wrangle in Primitives
 +
 +
string path = @path;
 +
s@path = re_replace(r"Deformed", "", path);
 
</pre>
 
</pre>

Revision as of 11:34, 14 February 2024

Houdini learning

Center Pivot

// In Pivot Translate in a Transform node

centroid(0,0)
centroid(0,1)
centroid(0,2)

Delete by Connectivity attribute

// In a Delete node, in Group (by example)

@class=7777

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

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;
// Next, with a Delete SOP: Group: @udim=$F - Pattern mode !*

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

// Remove small parts - In a Foreach connected piece loop
@size = (getbbox_size(0).x+getbbox_size(0).y+getbbox_size(0).z);

if(@size < chf("taille"))
removepoint(geoself(), @ptnum);

// Set @variant integer for Copytopoints (change objects number)
i@variant =floor(rand(@id)*3);

//// Get position difference between two objects, and match animation
// On Rest pose object:
v@fixe = 0;
@fixe.x = getbbox_center(0).x;
@fixe.y = getbbox_center(0).y;
@fixe.z = getbbox_center(0).z;
// On animated object:
v@anim = 0;
@anim.x = getbbox_center(0).x;
@anim.y = getbbox_center(0).y;
@anim.z = getbbox_center(0).z;
// After two previous AttrWrangles:
v@anim_offset = point(0, 'fixe', 1) - point(1, 'anim', 1);
// To match animation:
@P = point(0, "P", @ptnum) + point(1, 'anim_offset', 1);

//// Blend shape through a mask attribute - Posted by Cudarsjanis on Odforce
// Geo with mask attribute in first input, blend shape in second
v@P=lerp(v@P, point(1,'P',@ptnum), f@mask*ch('blend'));

//// Set a fixed normal attribute
v@z = set(0,1,0);

//// Place at world center
v@P -= getbbox_center(0);

Delete small pieces

// As seen on Sidefx forum, posted by paulboiii
// First create a measure SOP, set to per piece

// Then, in an attribwrangle set on primitives
float threshold = chf("Size_Threshold");
if ( f@area < threshold ) removeprim(0,@primnum,1);

Attribute Wrangle - Copy attribute from second input

// With same number of points on both inputs - From Bonsak on Sidefx.com

// Copy P from second input
@P = v@opinput1_P;

Bounding-box - Position Reference color

// As seen on https://houdinihelp.ru/ref/expression_cookbook.html

// In an attribwrangle set on primitives
@Cd.r = relbbox(0,@P).x;
@Cd.g = relbbox(0,@P).y;
@Cd.b = relbbox(0,@P).z;

Group by uv.y

// Thanks to https://vfxbrain.wordpress.com/2019/06/14/vex-snippets-2/

// In an attribwrangle set on points
if(@uv.y<chf("seuil")) @group_base = 1;

// ALTERNATIVE
@uv.x<0.2

Specify attribute value for one point

if (@ptnum == 322) f@mask=1;

Pscale by Bbox Y

//set pscale first

f@bboxY = relbbox(0,@P).y;
@pscale *= chramp("rampBbox",@bboxY)*4 ;

Delete primitives by height

if ( @P.y<chf("seuil") ) removeprim(0,@primnum,1);

Falloff geometry

// Get camOrigin

vector pt0 = point(1,'P',0);
v@raydir = normalize(  pt0 - @P )*-1;

@falloff = dot(v@raydir, @N);

// Promote raydir in Primitives

if ( f@falloff>chf("seuil") ) removeprim(0,@primnum,1);

Labs Maps Baker - Bake with UDIMs

// Add %(UDIM)d in the file path - don't need to check Output UDIMs

Gets the digits from node name

// Add `padzero(3,opdigits("."))`
// Add `padzero(3,opdigits(".."))` for previous node padding
// padzero(3,opdigits(".")) without hscript

Self-shadows in Mantra

// Add by example * ^RENDER_ground in Shadow Mask of every of your lights to exclude self-shadows

Search and replace in VEX

// To remove ShapeDeformed from Maya Alembics by example, in an Attribute Wrangle in Primitives

string path = @path;
s@path = re_replace(r"Deformed", "", path);
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