phaser/src/geom/intersects/RectangleToTriangle.js

A fast, free and fun HTML5 Game Framework for Desktop and Mobile web browsers from the team at Phaser Studio Inc.

/**
 * @author       Richard Davey <rich@phaser.io>
 * @copyright    2013-2025 Phaser Studio Inc.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

var LineToLine = require('./LineToLine');
var Contains = require('../rectangle/Contains');
var ContainsArray = require('../triangle/ContainsArray');
var Decompose = require('../rectangle/Decompose');

/**
 * Checks for intersection between Rectangle shape and Triangle shape.
 *
 * @function Phaser.Geom.Intersects.RectangleToTriangle
 * @since 3.0.0
 *
 * @param {Phaser.Geom.Rectangle} rect - Rectangle object to test.
 * @param {Phaser.Geom.Triangle} triangle - Triangle object to test.
 *
 * @return {boolean} A value of `true` if objects intersect; otherwise `false`.
 */
var RectangleToTriangle = function (rect, triangle)
{
    //  First the cheapest ones:

    if (
        triangle.left > rect.right ||
        triangle.right < rect.left ||
        triangle.top > rect.bottom ||
        triangle.bottom < rect.top)
    {
        return false;
    }

    var triA = triangle.getLineA();
    var triB = triangle.getLineB();
    var triC = triangle.getLineC();

    //  Are any of the triangle points within the rectangle?

    if (Contains(rect, triA.x1, triA.y1) || Contains(rect, triA.x2, triA.y2))
    {
        return true;
    }

    if (Contains(rect, triB.x1, triB.y1) || Contains(rect, triB.x2, triB.y2))
    {
        return true;
    }

    if (Contains(rect, triC.x1, triC.y1) || Contains(rect, triC.x2, triC.y2))
    {
        return true;
    }

    //  Cheap tests over, now to see if any of the lines intersect ...

    var rectA = rect.getLineA();
    var rectB = rect.getLineB();
    var rectC = rect.getLineC();
    var rectD = rect.getLineD();

    if (LineToLine(triA, rectA) || LineToLine(triA, rectB) || LineToLine(triA, rectC) || LineToLine(triA, rectD))
    {
        return true;
    }

    if (LineToLine(triB, rectA) || LineToLine(triB, rectB) || LineToLine(triB, rectC) || LineToLine(triB, rectD))
    {
        return true;
    }

    if (LineToLine(triC, rectA) || LineToLine(triC, rectB) || LineToLine(triC, rectC) || LineToLine(triC, rectD))
    {
        return true;
    }

    //  None of the lines intersect, so are any rectangle points within the triangle?

    var points = Decompose(rect);
    var within = ContainsArray(triangle, points, true);

    return (within.length > 0);
};

module.exports = RectangleToTriangle;