three.js/src/cameras/PerspectiveCamera.js

/**
 * @author mrdoob / http://mrdoob.com/
 * @author greggman / http://games.greggman.com/
 * @author zz85 / http://www.lab4games.net/zz85/blog
 */

THREE.PerspectiveCamera = function ( fov, aspect, near, far ) {

	THREE.Camera.call( this );

	this.fov = fov !== undefined ? fov : 50;
	this.aspect = aspect !== undefined ? aspect : 1;
	this.near = near !== undefined ? near : 0.1;
	this.far = far !== undefined ? far : 2000;

	this.updateProjectionMatrix();

};

THREE.PerspectiveCamera.prototype = Object.create( THREE.Camera.prototype );


/**
 * Uses Focal Length (in mm) to estimate and set FOV
 * 35mm (fullframe) camera is used if frame size is not specified;
 * Formula based on http://www.bobatkins.com/photography/technical/field_of_view.html
 */

THREE.PerspectiveCamera.prototype.setLens = function ( focalLength, frameHeight ) {

	if ( frameHeight === undefined ) frameHeight = 24;

	this.fov = 2 * THREE.Math.radToDeg( Math.atan( frameHeight / ( focalLength * 2 ) ) );
	this.updateProjectionMatrix();

}


/**
 * Sets an offset in a larger frustum. This is useful for multi-window or
 * multi-monitor/multi-machine setups.
 *
 * For example, if you have 3x2 monitors and each monitor is 1920x1080 and
 * the monitors are in grid like this
 *
 *   +---+---+---+
 *   | A | B | C |
 *   +---+---+---+
 *   | D | E | F |
 *   +---+---+---+
 *
 * then for each monitor you would call it like this
 *
 *   var w = 1920;
 *   var h = 1080;
 *   var fullWidth = w * 3;
 *   var fullHeight = h * 2;
 *
 *   --A--
 *   camera.setOffset( fullWidth, fullHeight, w * 0, h * 0, w, h );
 *   --B--
 *   camera.setOffset( fullWidth, fullHeight, w * 1, h * 0, w, h );
 *   --C--
 *   camera.setOffset( fullWidth, fullHeight, w * 2, h * 0, w, h );
 *   --D--
 *   camera.setOffset( fullWidth, fullHeight, w * 0, h * 1, w, h );
 *   --E--
 *   camera.setOffset( fullWidth, fullHeight, w * 1, h * 1, w, h );
 *   --F--
 *   camera.setOffset( fullWidth, fullHeight, w * 2, h * 1, w, h );
 *
 *   Note there is no reason monitors have to be the same size or in a grid.
 */

THREE.PerspectiveCamera.prototype.setViewOffset = function ( fullWidth, fullHeight, x, y, width, height ) {

	this.fullWidth = fullWidth;
	this.fullHeight = fullHeight;
	this.x = x;
	this.y = y;
	this.width = width;
	this.height = height;

	this.updateProjectionMatrix();

};


THREE.PerspectiveCamera.prototype.updateProjectionMatrix = function () {

	if ( this.fullWidth ) {

		var aspect = this.fullWidth / this.fullHeight;
		var top = Math.tan( THREE.Math.degToRad( this.fov * 0.5 ) ) * this.near;
		var bottom = -top;
		var left = aspect * bottom;
		var right = aspect * top;
		var width = Math.abs( right - left );
		var height = Math.abs( top - bottom );

		this.projectionMatrix.makeFrustum(
			left + this.x * width / this.fullWidth,
			left + ( this.x + this.width ) * width / this.fullWidth,
			top - ( this.y + this.height ) * height / this.fullHeight,
			top - this.y * height / this.fullHeight,
			this.near,
			this.far
		);

	} else {

		this.projectionMatrix.makePerspective( this.fov, this.aspect, this.near, this.far );

	}

};

THREE.PerspectiveCamera.prototype.clone = function () {

	var camera = new THREE.PerspectiveCamera();

	THREE.Camera.prototype.clone.call( this, camera );

	camera.fov = this.fov;
	camera.aspect = this.aspect;
	camera.near = this.near;
	camera.far = this.far;

	return camera;
};