rpg-dialogue-js/dist/tests/libs/plotboilerplate/src/ts/geomutils.ts

A simple roleplay game dialogue engine and editor.

/**
 * @author   Ikaros Kappler
 * @date     2019-02-03
 * @modified 2021-03-01 Added `wrapMax` function.
 * @version  1.1.0
 **/


import { Line } from "./Line";
import { Triangle } from "./Triangle";
import { Vertex } from "./Vertex";

/**
 * A collection of usefull geometry utilities.
 *
 * @global
 **/
export const geomutils = {

    /**
     * Compute the n-section of the angle – described as a triangle (A,B,C) – in point A.
     *
     * @param {Vertex} pA - The first triangle point.
     * @param {Vertex} pB - The second triangle point.
     * @param {Vertex} pC - The third triangle point.
     * @param {number} n - The number of desired angle sections (example: 2 means the angle will be divided into two sections, 
     *                      means an returned array with length 1, the middle line).
     *
     * @return {Line[]} An array of n-1 lines secting the given angle in point A into n equal sized angle sections. The lines' first vertex is A.
     */
    nsectAngle( pA:Vertex, pB:Vertex, pC:Vertex, n:number ) : Array<Line> {
	const triangle : Triangle  = new Triangle( pA, pB, pC );
	const lineAB : Line        = new Line( pA, pB );
	const lineAC : Line        = new Line( pA, pC );
	// Compute the difference; this is the angle between AB and AC
	var insideAngle : number   = lineAB.angle( lineAC );
	// We want the inner angles of the triangle, not the outer angle;
	//   which one is which depends on the triangle 'direction'
	const clockwise : boolean  = triangle.determinant() > 0;
	
	// For convenience convert the angle [-PI,PI] to [0,2*PI]
	if( insideAngle < 0 )
	    insideAngle = 2*Math.PI + insideAngle;
	if( !clockwise )
	    insideAngle = (2*Math.PI - insideAngle) * (-1);  

	// Scale the rotated lines to the max leg length (looks better)
	const lineLength : number  = Math.max( lineAB.length(), lineAC.length() );
	const scaleFactor : number = lineLength/lineAB.length();

	var result : Array<Line> = [];
	for( var i = 1; i < n; i++ ) {
	    // Compute the i-th inner sector line
	    result.push( new Line( pA, pB.clone().rotate((-i*(insideAngle/n)), pA) ).scale(scaleFactor) as Line ); 
	}
	return result; 
    },

    /**
     * Wrap the value (e.g. an angle) into the given range of [0,max).
     *
     * @name wrapMax
     * @param {number} x - The value to wrap.
     * @param {number} max - The max bound to use for the range.
     * @return {number} The wrapped value inside the range [0,max).
     */
    wrapMax( x:number, max:number ) : number {
	// Found at
	//    https://stackoverflow.com/questions/4633177/c-how-to-wrap-a-float-to-the-interval-pi-pi
	return (max + (x%max)) % max;
    },
    
    /**
     * Wrap the value (e.g. an angle) into the given range of [min,max).
     *
     * @name wrapMinMax
     * @param {number} x - The value to wrap.
     * @param {number} min - The min bound to use for the range.
     * @param {number} max - The max bound to use for the range.
     * @return {number} The wrapped value inside the range [min,max).
     */
    // Currently un-used
    wrapMinMax( x:number, min:number, max:number ) : number {		
	return min + geomutils.wrapMax( x - min, max - min );
    } 
};