// Create 2 vectors in the plane orthonormal to the vector described by two locators, locator1 and locator2
//
// illustrates the tutorial by Paul Bourke: pbourke@swin.edu.au
// http://astronomy.swin.edu.au/~pbourke/geometry/disk/
//
// implemented in mel by Dan Wills: dan@rsp.com.au
//
// Feb 2003

//grab locator1 as P1
float $P1loc[3];
$P1loc[0] = `getAttr locator1.translateX`;
$P1loc[1] = `getAttr locator1.translateY`;
$P1loc[2] = `getAttr locator1.translateZ`;

//grab locator2 as P2
float $P2loc[3];
$P2loc[0] = `getAttr locator2.translateX`;
$P2loc[1] = `getAttr locator2.translateY`;
$P2loc[2] = `getAttr locator2.translateZ`;

//get random sample point P
float $randpointP[3] = {`rand -2 2`,`rand -2 2`,`rand -2 2`};

//put a locator there for illustration.
spaceLocator -p $randpointP[0] $randpointP[1] $randpointP[2];

//calculate vector from P1 to P
float $PP1vec[3] = { $randpointP[0] - $P1loc[0],
                    $randpointP[1] - $P1loc[1],
                    $randpointP[2] - $P1loc[2]  };

//create P1 to P vector
curve -d 1 -ws -p $P1loc[0] $P1loc[1] $P1loc[2] -p ($P1loc[0] + $PP1vec[0]) ($P1loc[1] + $PP1vec[1]) ($P1loc[1] + $PP1vec[2]);

float $P2P1vec[3] = { $P2loc[0] - $P1loc[0],
                     $P2loc[1] - $P1loc[1],
                     $P2loc[2] - $P1loc[2] };

float $crossprodR[3] = crossProduct($PP1vec,$P2P1vec,0,0);
float $crossprodS[3] = crossProduct($crossprodR,$P2P1vec,0,0);

//create vector from P1 to P2:
curve -d 1 -ws -p $P1loc[0] $P1loc[1] $P1loc[2]  -p $P2loc[0] $P2loc[1] $P2loc[2];

//create cross product vector R:
curve -d 1 -ws -p $P1loc[0] $P1loc[1] $P1loc[2] -p ($P1loc[0] + $crossprodR[0]) ($P1loc[1] + $crossprodR[1]) ($P1loc[2] + $crossprodR[2]);

//create cross product vector S:
curve -d 1 -ws -p $P1loc[0] $P1loc[1] $P1loc[2] -p ($P1loc[0] + $crossprodS[0]) ($P1loc[1] + $crossprodS[1]) ($P1loc[2] + $crossprodS[2]);