Separating Axis Theorem Collision Testing

sat_6.js

polygon.testWith = function (otherPolygon) {
    // get all edges
    const edges = [];
    for (let i = 0; i < polygon.edges.length; i++) {
        edges.push(polygon.edges[i]);
    }
    for (let i = 0; i < otherPolygon.edges.length; i++) {
        edges.push(otherPolygon.edges[i]);
    }
    // build all axis and project
    for (let i = 0; i < edges.length; i++) {
        // get axis
        const length = Math.sqrt(edges[i].y * edges[i].y + edges[i].x * edges[i].x);
        const axis = {
            x: -edges[i].y / length,
            y: edges[i].x / length,
        };
        // project polygon under axis
        const { min: minA, max: maxA } = polygon.projectInAxis(axis.x, axis.y);
        const { min: minB, max: maxB } = otherPolygon.projectInAxis(axis.x, axis.y);
        if (intervalDistance(minA, maxA, minB, maxB) > 0) {
            return false;
        }
    }
    return true;
};