three.js/src/math/Matrix3.js

/**
 * @author alteredq / http://alteredqualia.com/
 * @author WestLangley / http://github.com/WestLangley
 * @author bhouston / http://clara.io
 * @author tschw
 */

THREE.Matrix3 = function () {

	this.elements = new Float32Array( [

		1, 0, 0,
		0, 1, 0,
		0, 0, 1

	] );

	if ( arguments.length > 0 ) {

		console.error( 'THREE.Matrix3: the constructor no longer reads arguments. use .set() instead.' );

	}

};

THREE.Matrix3.prototype = {

	constructor: THREE.Matrix3,

	set: function ( n11, n12, n13, n21, n22, n23, n31, n32, n33 ) {

		var te = this.elements;

		te[ 0 ] = n11; te[ 1 ] = n21; te[ 2 ] = n31;
		te[ 3 ] = n12; te[ 4 ] = n22; te[ 5 ] = n32;
		te[ 6 ] = n13; te[ 7 ] = n23; te[ 8 ] = n33;

		return this;

	},

	identity: function () {

		this.set(

			1, 0, 0,
			0, 1, 0,
			0, 0, 1

		);

		return this;

	},

	clone: function () {

		return new this.constructor().fromArray( this.elements );

	},

	copy: function ( m ) {

		var me = m.elements;

		this.set(

			me[ 0 ], me[ 3 ], me[ 6 ],
			me[ 1 ], me[ 4 ], me[ 7 ],
			me[ 2 ], me[ 5 ], me[ 8 ]

		);

		return this;

	},

	setFromMatrix4: function( m ) {

		var me = m.elements;

		this.set(

			me[ 0 ], me[ 4 ], me[  8 ],
			me[ 1 ], me[ 5 ], me[  9 ],
			me[ 2 ], me[ 6 ], me[ 10 ]

		);

		return this;

	},

	applyToVector3Array: function () {

		var v1;

		return function applyToVector3Array( array, offset, length ) {

			if ( v1 === undefined ) v1 = new THREE.Vector3();
			if ( offset === undefined ) offset = 0;
			if ( length === undefined ) length = array.length;

			for ( var i = 0, j = offset; i < length; i += 3, j += 3 ) {

				v1.fromArray( array, j );
				v1.applyMatrix3( this );
				v1.toArray( array, j );

			}

			return array;

		};

	}(),

	applyToBuffer: function () {

		var v1;

		return function applyToBuffer( buffer, offset, length ) {

			if ( v1 === undefined ) v1 = new THREE.Vector3();
			if ( offset === undefined ) offset = 0;
			if ( length === undefined ) length = buffer.length / buffer.itemSize;

			for ( var i = 0, j = offset; i < length; i ++, j ++ ) {

				v1.x = buffer.getX( j );
				v1.y = buffer.getY( j );
				v1.z = buffer.getZ( j );

				v1.applyMatrix3( this );

				buffer.setXYZ( v1.x, v1.y, v1.z );

			}

			return buffer;

		};

	}(),

	multiplyScalar: function ( s ) {

		var te = this.elements;

		te[ 0 ] *= s; te[ 3 ] *= s; te[ 6 ] *= s;
		te[ 1 ] *= s; te[ 4 ] *= s; te[ 7 ] *= s;
		te[ 2 ] *= s; te[ 5 ] *= s; te[ 8 ] *= s;

		return this;

	},

	determinant: function () {

		var te = this.elements;

		var a = te[ 0 ], b = te[ 1 ], c = te[ 2 ],
			d = te[ 3 ], e = te[ 4 ], f = te[ 5 ],
			g = te[ 6 ], h = te[ 7 ], i = te[ 8 ];

		return a * e * i - a * f * h - b * d * i + b * f * g + c * d * h - c * e * g;

	},

	getInverse: function ( matrix, throwOnDegenerate ) {

		if ( matrix instanceof THREE.Matrix4 ) {

			console.error( "THREE.Matrix3.getInverse no longer takes a Matrix4 argument." );

		}

		var me = matrix.elements,
			te = this.elements,

			n11 = me[ 0 ], n21 = me[ 1 ], n31 = me[ 2 ],
			n12 = me[ 3 ], n22 = me[ 4 ], n32 = me[ 5 ],
			n13 = me[ 6 ], n23 = me[ 7 ], n33 = me[ 8 ],

			t11 = n33 * n22 - n32 * n23,
			t12 = n32 * n13 - n33 * n12,
			t13 = n23 * n12 - n22 * n13,

			det = n11 * t11 + n21 * t12 + n31 * t13;

		if ( det === 0 ) {

			var msg = "THREE.Matrix3.getInverse(): can't invert matrix, determinant is 0";

			if ( throwOnDegenerate || false ) {

				throw new Error( msg );

			} else {

				console.warn( msg );

			}

			return this.identity();
		}
		
		var detInv = 1 / det;

		te[ 0 ] = t11 * detInv;
		te[ 1 ] = ( n31 * n23 - n33 * n21 ) * detInv;
		te[ 2 ] = ( n32 * n21 - n31 * n22 ) * detInv;

		te[ 3 ] = t12 * detInv;
		te[ 4 ] = ( n33 * n11 - n31 * n13 ) * detInv;
		te[ 5 ] = ( n31 * n12 - n32 * n11 ) * detInv;

		te[ 6 ] = t13 * detInv;
		te[ 7 ] = ( n21 * n13 - n23 * n11 ) * detInv;
		te[ 8 ] = ( n22 * n11 - n21 * n12 ) * detInv;

		return this;

	},

	transpose: function () {

		var tmp, m = this.elements;

		tmp = m[ 1 ]; m[ 1 ] = m[ 3 ]; m[ 3 ] = tmp;
		tmp = m[ 2 ]; m[ 2 ] = m[ 6 ]; m[ 6 ] = tmp;
		tmp = m[ 5 ]; m[ 5 ] = m[ 7 ]; m[ 7 ] = tmp;

		return this;

	},

	flattenToArrayOffset: function ( array, offset ) {

		console.warn( "THREE.Matrix3: .flattenToArrayOffset is deprecated " +
				"- just use .toArray instead." );

		return this.toArray( array, offset );

	},

	getNormalMatrix: function ( matrix4 ) {

		return this.setFromMatrix4( matrix4 ).getInverse( this ).transpose();

	},

	transposeIntoArray: function ( r ) {

		var m = this.elements;

		r[ 0 ] = m[ 0 ];
		r[ 1 ] = m[ 3 ];
		r[ 2 ] = m[ 6 ];
		r[ 3 ] = m[ 1 ];
		r[ 4 ] = m[ 4 ];
		r[ 5 ] = m[ 7 ];
		r[ 6 ] = m[ 2 ];
		r[ 7 ] = m[ 5 ];
		r[ 8 ] = m[ 8 ];

		return this;

	},

	fromArray: function ( array ) {

		this.elements.set( array );

		return this;

	},

	toArray: function ( array, offset ) {

		if ( array === undefined ) array = [];
		if ( offset === undefined ) offset = 0;

		var te = this.elements;

		array[ offset ] = te[ 0 ];
		array[ offset + 1 ] = te[ 1 ];
		array[ offset + 2 ] = te[ 2 ];

		array[ offset + 3 ] = te[ 3 ];
		array[ offset + 4 ] = te[ 4 ];
		array[ offset + 5 ] = te[ 5 ];

		array[ offset + 6 ] = te[ 6 ];
		array[ offset + 7 ] = te[ 7 ];
		array[ offset + 8 ]  = te[ 8 ];

		return array;

	}

};