//
// vmvInstanceObjects [name_of_the_particle_object]
//
// Prebaked simple solution for creating shatter/explosion type of effects with particle instancer - ie. script 
// replaces every selected object with a particle controlled instance what can be animated by using fields 
// or expressions or whatever.
//
// Workflow:
//
//			Source the script.
//
//			Select all the objects you want to instance and type vmvInstanceObjects explodeMe (for example).
//
//			Script will create particle object with custom attributes feeded into instancer, and hide original
//			object geometry (which new home is in origin now).
//
//			Simple runtime expression is controlling the rotation of instanced objects based on particles velocity.
//			Scalar attributes rotMult & massMult are used to tune animation.
//
//			Fake creation expression is used, so animation should start around frame 0 (which of course can be changed).
//			If there seems to be a problem with the playback, adjust particle start frame accordingly 
//			and/or edit the expressions...
//
// V-M Vasama 2007 / vm_vasama@hotmail.com
//

global proc vmvInstanceObjects( string $part )
{
	string $partName = $part; 	//pass argument			
	string $object, $objects[];			
	int $i, $numObjects;	
	float $objectIndex, $partPos[4];
							
	//get number of selected objects		
	$objects = `ls -sl`;
	$numObjects = size($objects);
	
	//create initial particle object 	
	particle -n $partName;
		
	//and add custom attributes	
	
	//indexPP (float)
	addAttr -ln indexPP0 -dt doubleArray ( $partName + "Shape" );
	addAttr -ln indexPP -dt doubleArray ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".indexPP" );
		
	//rotatePP (vector)
	addAttr -ln rotatePP0 -dt vectorArray ( $partName + "Shape" );
	addAttr -ln rotatePP -dt vectorArray ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".rotatePP" );

	//rotateInitPP (vector)
	addAttr -ln rotateInitPP0 -dt vectorArray ( $partName + "Shape" );
	addAttr -ln rotateInitPP -dt vectorArray ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".rotateInitPP" );	
	
	//rotMultMin (scalar)
	addAttr -ln rotMultMin -at double ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".rotMultMin" );	
		
	//rotMultMax (scalar)
	addAttr -ln rotMultMax -at double ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".rotMultMax" );
	
	//massMultMin (scalar)
	addAttr -ln massMultMin -at double ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".massMultMin" );		
										
	//massMultMax (scalar)
	addAttr -ln massMultMax -at double ( $partName + "Shape" );
	setAttr -e -keyable true ( $partName + "Shape" + ".massMultMax" );		
	
	//main loop: loop through selected objects and
	//assign particle at the center of each object
	//then move objects to origin and zero transforms
	for ( $i=0; $i < $numObjects; $i++ ) {	
		
		//select current object
		$object = $objects[$i];
		select $object;
		//freeze transformations
		makeIdentity -apply true -t 1 -r 1 -s 1 -n 0;
		//center pivot
		xform -cp;
		//get current particle wrld pos
		$partPos = `xform -q -rp ($object)`;
		
		//update index
		$objectIndex = $i;
		
		//calculate volume of the current object geometry
		float $bb[] = `xform -q -ws -bb $object`;
		float $x = abs( $bb[3] - $bb[0] );
		float $y = abs( $bb[4] - $bb[1] );
		float $z = abs( $bb[5] - $bb[2] );
		vector $vv = <<$x, $y, $z>>;
		
		//get length of total vector, use this as the particle's mass
		float $vol = mag( $vv ) + 0.1;				
				
		//emit particle to object position with attrs
		emit 	-object ($partName)
				-position $partPos[0] $partPos[1] $partPos[2]
				-attribute mass -floatValue $vol
				-attribute indexPP -floatValue $objectIndex;				
				
		//move object to center because of the instancer
		createPrimitive nullObject;
		$loc = `ls -sl`;
		
		//snap align selected objects to locator (0 0 0)
		select $object;		
		select -add $loc;
		align -atl -x Mid -y Mid -z Mid;
		
		//delete locator		
		select $loc;
		delete;
	
		//freeze transformations of object
		select $object;
		makeIdentity -apply true -t 1 -r 1 -s 1 -n 0;					
		
		//hide object
		HideSelectedObjects;
	}
	
	//save initial state of particles
	saveInitialState ($partName);
	
	//create instancer
	select $objects;
	select -add $partName;
	
	string $objectList;
	
	//build string with objects
	for ( $i = 0; $i < $numObjects ; $i++ ) {		
		$objectList += " -object " + $objects[$i];
	}
	
	//final launch pre-emptive strike command
	eval ( "particleInstancer -addObject" + $objectList + " -cycle None -cycleStep 1 -cycleStepUnits Frames -levelOfDetail Geometry -rotationUnits Degrees -rotationOrder XYZ -position worldPosition -age age -objectIndex indexPP -rotation rotatePP " + $partName );
								
	//modify particle runtime expression	
	//and create a fake creation expression just to be sure everything works
	string $runTime = 	"if ( frame <= 2.0 ) { \n" +
						"	rotateInitPP = << rand( rotMultMin, rotMultMax ), rand( rotMultMin, rotMultMax ), rand( rotMultMin, rotMultMax ) >>; \n" +					
						"	mass *= rand( massMultMin, massMultMax ); \n" +
						"} else { \n" +											
						"	vector $vel = velocity; \n" + 
						"	vector $rot = rotateInitPP; \n " +
						"	rotatePP += << $vel.x * $rot.x, $vel.y * $rot.y, $vel.z * $rot.z >>; \n" +												
						"} \n"						
						;
						
	dynExpression -rbd -s $runTime ($partName + "Shape");
	
	//set particle start frame to 0 to accommodate fake creation expression
	setAttr ( $partName + "Shape" + ".stf" ) 0.0;
	
	//set initial attributes
	setAttr ( $partName + "Shape" + ".rotMultMin" )  -1.0;
	setAttr ( $partName + "Shape" + ".rotMultMax" )   1.0;
	setAttr ( $partName + "Shape" + ".massMultMin" )  1.0;
	setAttr ( $partName + "Shape" + ".massMultMax" )  1.0;
	
	//cheers
	print("\nDone.\n");
	
}