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Random Motion Path Code?
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  • frujo23
  • Posted: 20 January 2011 09:24 AM
  • Total Posts: 41
  • Joined: 19 June 2008 04:59 AM

I need a way of making an object pick a random point on a grid like say (X = rand(-25,25) Y = rand(-25,25)) then move towards that point. If it reaches that point then it picks a new point then repeats. I need this to run in the expression . Please Help!


Replies: 0
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  • raym4n
  • Posted: 02 February 2011 09:49 PM

//- random position expression by Pavel Pehlivanov -
//- ------------------2011-02-03--------------------
//---- to setup scene for this add custom attrs ----
//------ "randX" and "randY" to target object ------
//--------------------------------------------------

$myObj = "pCube1"; //target object name
$xMin = -10; //x min var
$xMax = 10; //x max var
$yMin = -10; //y min var
$yMax = 10; //y max var
$threshold = .05; //if object reaches distance below this var it creates new position
$spd = .1; //speed multiplier

//get object pos
float $crX = getAttr ($myObj+".tx");
float $rnX = getAttr ($myObj+".randX");
float $crY = getAttr ($myObj+".ty");
float $rnY = getAttr ($myObj+".randY");

//calculate threshold
$tX=abs($crX-$rnX);
$tY=abs($crY-$rnY);

if(($tX<$threshold)&&($tY<$threshold)){
 //if wanted position is reached create new random pos
 setAttr ($myObj+".randX") (rand($xMin,$xMax));
 setAttr ($myObj+".randY") (rand($yMin,$yMax));
}else{
 //else change object position
 setAttr ($myObj+".tx") ($crX+(($rnX-$crX)*$spd));
 setAttr ($myObj+".ty") ($crY+(($rnY-$crY)*$spd));
}

Ask if you have any questions.


Replies: 1
/img/forum/dark/default_avatar.png

first off thank you so much, this has been boggling my mind for the longest time.

second this happens after I try running it.

// Error: No object matches name: pCube1.randX //
// Error: An execution error occured in the expression expression1. //

Author: frujo23
Replied: 14 March 2011 09:39 AM  
avatar
  • raym4n
  • Posted: 02 February 2011 10:13 PM

Another implementation using velocity vector:

//- random position expression by Pavel Pehlivanov -
//- ------------------2011-02-03--------------------
//---- to setup scene for this add custom attrs ----
//---- "randX" "randY" "randZ" to target object ----
//--------------------------------------------------

$myObj = "pCube1"; //target object name
$xMin = -10; //x min var
$xMax = 10; //x max var
$yMin = -10; //y min var
$yMax = 10; //y max var
$zMin = -10; //z min var
$zMax = 10; //z max var
$spd = .5; //speed 

//get object pos
float $crX = getAttr ($myObj+".tx");
float $rnX = getAttr ($myObj+".randX");
float $crY = getAttr ($myObj+".ty");
float $rnY = getAttr ($myObj+".randY");
float $crZ = getAttr ($myObj+".tz");
float $rnZ = getAttr ($myObj+".randZ");

vector $currPos = <<$crX,$crY,$crZ>>;
vector $targetPos = <<$rnX,$rnY,$rnZ>>;
//compute velocity
vector $targetVelocity = $targetPos-$currPos;
vector $targetUnitVelocity = unit($targetVelocity);
float $targetDist = mag($targetVelocity);

//if current velocity distance is less than speed calculate new pos
if($targetDist<$spd){
 //move object to desired pos
 setAttr ($myObj+".tx") ($rnX);
 setAttr ($myObj+".ty") ($rnY);
 setAttr ($myObj+".tz") ($rnZ);
 //create new target pos
 setAttr ($myObj+".randX") (rand($xMin,$xMax));
 setAttr ($myObj+".randY") (rand($yMin,$yMax));
 setAttr ($myObj+".randZ") (rand($zMin,$zMax));
}else{
 //else move object using vector mult by speed
 setAttr ($myObj+".tx") ($crX+($spd*$targetUnitVelocity.x));
 setAttr ($myObj+".ty") ($crY+($spd*$targetUnitVelocity.y));
 setAttr ($myObj+".tz") ($crZ+($spd*$targetUnitVelocity.z));
}

Replies: 0




   
 
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