skyburchard

//////////////////////////
// -1 to 1 remap to 0 to 1
//////////////////////////

x = x / 2 + 0.5;

//////////////////////////
// 0 to 1 remap to -1 to 1
//////////////////////////

skyburchard

 ////////////////////////////////////////////////////////
 // rotate a point around another point using quaternions
 
 // set quaterion by vector
 var quat = Quaternion.LookRotation(Vector3 forward, Vector3 upwards = Vector3.up);
 
 // set quaternion by angle
 var quat = Quaternion.AngleAxis(float angle, Vector3 axis);
 
 // rotate around pivit point

skyburchard

float width = chf("width");
float depth = chf("depth");

float halfWidth = width * 0.5;
float halfDepth = depth * 0.5;

vector v0 = set( halfWidth, 0,  halfDepth);
vector v1 = set(-halfWidth, 0,  halfDepth);
vector v2 = set(-halfWidth, 0, -halfDepth);
vector v3 = set( halfWidth, 0, -halfDepth);

skyburchard

////////////////////////////////
// houdini attributes and groups
////////////////////////////////

///////////////////////
// attributes as groups
// credit here: http://www.tokeru.com/cgwiki/?title=Houdini
// the below can be entered as expressions in any goup field
// not spaces, no semi colon, must be conditional, must be cast using "s, i, f", etc
// floats don't need casting

skyburchard

///////////////////////////////////////////////
// glsl snippets: credit given where i could //
///////////////////////////////////////////////

///////////////////
// inverse matrices
// credit to: https://github.com/glslify/glsl-inverse/blob/master/index.glsl

float inverse(float m) {
  return 1.0 / m;

skyburchard

///////////////////////
// houdini vex snippets
///////////////////////

// get angle between two vectors ( 0 - 360 dergees )

float angleBetween ( vector v1; vector v2 ) {
    // define up vector
    vector up = {0.0, 1.0, 0.0};