Joy Of Vex

• https://www.tokeru.com/cgwiki/JoyOfVex.html
  • https://github.com/jtomori/vex_tutorial
• Houdini Hangout - The Joy of VEX
• TWA 후디니의 정석 - JOY_OF_VEX(한국어.ver)
• https://github.com/kiryha/Houdini/wiki/vex-for-artists

List

• JoyOfVex01 basic assignment, component assignment, arithmetic manipulation
• JoyOfVex02 length and distance functions, animate with @Time
• JoyOfVex03 clamp and fit, waves
• JoyOfVex04 chramp, using on attrib components, on time, on reranging outputs
• JoyOfVex05 modulo, more arithmetic tricks (quantising), but show that often a chramp is easier (eg stepped chramp);
• JoyOfVex06 point wrangle vs prim wrangle vs detail wrangle, user defined attributes
• JoyOfVex07 using the other inputs on wrangles, do things to geometry based on other geometry
• JoyOfVex08 noise, various types, how it can be scaled, vector vs scalar noise, why you might use vops here instead
• JoyOfVex09 dot and cross product, fake lighting combing normals to a surface, vector maths primer
• JoyOfVex10 relpointbbox
• JoyOfVex11 if statements
• JoyOfVex12 nearpoints, arrays
• JoyOfVex13 for loops (ties nicely into arrays)
• JoyOfVex14 creating geometry, deleting geometry, debugging vex
• JoyOfVex15 copy sop, simple instance attributes (pscale)
• JoyOfVex16 copy sop, midweight instance attributes (scale, N)
• JoyOfVex17 copy sop, orient, quaternions
• JoyOfVex18 intrinsics
• JoyOfVex19 primuv, xyzdist
• JoyOfVex20 pointclouds, further learning

01

• Attribute Wrangle
  • Runs a VEX snippet to modify attribute values.
  • Wrangle : 다루다

@Cd = @N;
@Cd = @P;
@Cd = @ptnum/@numpt;
@Cd = float(@ptnum) / ch('scale');
@Cd = sin(@ptnum);

https://www.sidefx.com/docs/houdini/hom/hou/Geometry.html https://www.sidefx.com/docs/houdini/hom/hou/Point.html https://docs.python.org/3.13/library/math.html https://www.sidefx.com/docs/houdini/hom/hou/index.html#parmtemplates_group

node = hou.pwd()
geo = node.geometry()

if not geo.findPointAttrib("Cd"):
    geo.addAttrib(hou.attribType.Point, "Cd", (1.0, 1.0, 1.0))

if not geo.findPointAttrib("N"):
    geo.addAttrib(hou.attribType.Point, "N", (0.0, 1.0, 0.0))

points = geo.points()

numpt = len(geo.points())                # @numpt
numpt = geo.intrinsicValue("pointcount") # @numpt

for point in points:
    P     = point.position()       # @P
    ptnum = point.number()         # @ptnum
    N     = point.attribValue("N") # @N

    point.setAttribValue("Cd", P)

import math

radian = 1.0
sin_value = math.sin(radian)

def AddParameters():
    parameters = [
        # hou.FloatParmTemplate(name, label, num_components, ...)
        hou.FloatParmTemplate("scale", "scale", 1, default_value=(1.0,), min=0.0, max=10.0),
    ]

    node = hou.pwd()
    parm_template_group = node.parmTemplateGroup()
    for param in parameters:
        param_name = param.name()
        if not node.parm(param_name):
            parm_template_group.append(param)
    node.setParmTemplateGroup(parm_template_group)

02

length(@P) == distance(@P, {0, 0, 0})

fit(v, in_min, in_max, out_min, out_max);

@Time : Float time ($T) |

03

float d = length(@P);
d *= ch('v_scale');
d += @Time;
@P.y = sin(d);

clamp(v, min, max);

04

chramp

05

trunc

06

::pass

07

https://www.sidefx.com/docs/houdini/vex/functions/minpos.html minpos VEX function Given a position in world space, returns the position of the closest point on a given geometry.

https://www.sidefx.com/docs/houdini/vex/functions/nearpoint.html nearpoint VEX function Finds the closest point in a geometry.

@P = point(1, 'P', @ptnum); @P = @opinput1_P;

08

noise curlnoise pnoise

09

dot cross

10

normalize relpointbbox

11

if

12

13

foreach( element; array)
{
    // do things to element
}

for ( starting value; test; value increment)
{

}

14

addpoint // removepoint addprim // removeprim addvertex // removevertex

15

::pass

16

::pass

17

quaternion

float angle = ch('angle');
vector axis = chv('axis');

@orient = quaternion(angle, axis);

@N = {0,1,0};
float s = sin(@Time);
float c = cos(@Time);
@up = set(s,0,c);

@orient = quaternion(maketransform(@N, @up));

matrix3 m = ident();
@orient = quaternion(m);


vector rot = radians(chv('euler'));
@orient = eulertoquaternion( rot, 0);


vector4 a = {0,0,0,1};
vector4 b = quaternion({0,1,0}*$PI/2);
@orient = slerp(a, b, ch('blend') );


@orient = qmultiply(@orient, extrarot);
matrix m = qconvert(@orient);

radians qconvert

https://www.sidefx.com/docs/houdini/vex/attribtypeinfo_suite.html Sets the meaning of an attribute in geometry. int setattribtypeinfo(int geohandle, string attribclass, string name, string typeinfo)

18

matrix3 m = ident();
setprimintrinsic(0, 'transform', 0, m);

matrix3 m = matrix3( myfancy4x4matrix);
matrix pft = primintrinsic(0,'packedfulltransform',@ptnum);
matrix3 rotandscale = matrix3(pft);
3@b = rotandscale;

19

vector uv = chv('uv');

@P = primuv(1,'P',0,uv);
@N = primuv(1,'N',0,uv);

i@primid;
v@uv;
@dist;

@dist = xyzdist(1,@P, @primid, @uv);

@P = primuv(1,'P',@primid, @uv);

20

int pts[] = nearpoints(1,@P,ch('d'),25);
int pt;
vector pos;
foreach (pt; pts)
{
  pos = point(1,'P',pt);
  addpoint(0,pos);
}


int pts[] = pcfind(1,'P',@P,ch('d'),25);
int pt;
vector pos;
foreach (pt; pts)
{
  pos = point(1,'P',pt);
  addpoint(0,pos);
}

pcopen pcfilter

int pc = pcopen(0,'P',@P, ch('dist'), chi('maxpoints'));
@Cd = pcfilter(pc, 'Cd');