xsandra/system/utils/collision/polygonPolygonCollision.js

Javascript Game Engine

module.exports = function polygonPolygon(polygon1, polygon2){
    //https://github.com/davidfig/intersects/blob/master/polygon-polygon.js
    var points1 = []
    var points2 = []
    for(let i=1;i<size(polygon1.coordinates);i++){
      points1.push(polygon1.coordinates[`x${i}`])
      points1.push(polygon1.coordinates[`y${i}`])
    }
    for(let i=1;i<size(polygon1.coordinates);i++){
      points2.push(polygon2.coordinates[`x${i}`])
      points2.push(polygon2.coordinates[`y${i}`])
    }
    var a = points1
    var b = points2
    var polygons = [a, b]
    var minA, maxA, projected, minB, maxB, j
    for (var i = 0; i < polygons.length; i++)
    {
        var polygon = polygons[i]
        for (var i1 = 0; i1 < polygon.length; i1 += 2)
        {
            var i2 = (i1 + 2) % polygon.length
            var normal = { x: polygon[i2 + 1] - polygon[i1 + 1], y: polygon[i1] - polygon[i2] }
            minA = maxA = null
            for (j = 0; j < a.length; j += 2)
            {
                projected = normal.x * a[j] + normal.y * a[j + 1]
                if (minA === null || projected < minA)
                {
                    minA = projected
                }
                if (maxA === null || projected > maxA)
                {
                    maxA = projected
                }
            }
            minB = maxB = null
            for (j = 0; j < b.length; j += 2)
            {
                projected = normal.x * b[j] + normal.y * b[j + 1]
                if (minB === null || projected < minB)
                {
                    minB = projected
                }
                if (maxB === null || projected > maxB)
                {
                    maxB = projected
                }
            }
            if (maxA < minB || maxB < minA)
            {
                return false
            }
        }
    }
    return true
}
 
size = function(obj) {
    var size = 0, key;
    for (key in obj) {
        if (obj.hasOwnProperty(key)) size++;
    }
    return size;
};