esengine/source/src/Physics/Shapes/ShapeCollisions/ShapeCollisions.ts

class ShapeCollisions {
    public static polygonToPolygon(first: Polygon, second: Polygon){
        let result = new CollisionResult();
        let isIntersecting = true;

        let firstEdges = first.edgeNormals;
        let secondEdges = second.edgeNormals;
        let minIntervalDistance = Number.POSITIVE_INFINITY;
        let translationAxis = new Vector2();
        let polygonOffset = Vector2.subtract(first.position, second.position);
        let axis: Vector2;
        
        for (let edgeIndex = 0; edgeIndex < firstEdges.length + secondEdges.length; edgeIndex ++){
            if (edgeIndex < firstEdges.length){
                axis = firstEdges[edgeIndex];
            } else {
                axis = secondEdges[edgeIndex - firstEdges.length];
            }

            let minA = 0;
            let minB = 0;
            let maxA = 0;
            let maxB = 0;
            let intervalDist = 0;
            this.getInterval(axis, first, minA, maxA);
            this.getInterval(axis, second, minB, maxB);
        }
    }

    public static getInterval(axis: Vector2, polygon: Polygon, min: number, max: number){
        let dot = Vector2.dot(polygon.points[0], axis);
        min = max = dot;

        for (let i = 1; i < polygon.points.length; i++){
            dot = Vector2.dot(polygon.points[i], axis);
            if (dot < min){
                min = dot;
            }else if(dot > max){
                max = dot;
            }
        }
    }

    public static circleToPolygon(circle: Circle, polygon: Polygon){
        let result = new CollisionResult();

        let poly2Circle = Vector2.subtract(circle.position, polygon.position);

        let gpp = Polygon.getClosestPointOnPolygonToPoint(polygon.points, poly2Circle);
        let closestPoint = gpp.closestPoint;
        let distanceSquared: number = gpp.distanceSquared;
        result.normal = gpp.edgeNormal;

        let circleCenterInsidePoly = polygon.containsPoint(circle.position);
        if (distanceSquared > circle.radius * circle.radius && !circleCenterInsidePoly)
            return result;

        let mtv: Vector2;
        if (circleCenterInsidePoly){
            mtv = Vector2.multiply(result.normal, new Vector2(Math.sqrt(distanceSquared) - circle.radius, Math.sqrt(distanceSquared) - circle.radius));
        }else{
            if (distanceSquared == 0){
                mtv = Vector2.multiply(result.normal, new Vector2(circle.radius, circle.radius));
            }else{
                let distance = Math.sqrt(distanceSquared);
                // mtv = Vector2.multiply( -Vector2.subtract(poly2Circle, closestPoint), new Vector2((circle.radius - distanceSquared) / distance))
            }
        }
    }

    public static circleToRect(circle: Circle, box: Box): CollisionResult{
        let result = new CollisionResult();
        let closestPointOnBounds = box.bounds.getClosestPointOnRectangleBorderToPoint(circle.position).res;

        if (box.containsPoint(circle.position)){
            result.point = closestPointOnBounds;

            let safePlace = Vector2.add(closestPointOnBounds, Vector2.subtract(result.normal, new Vector2(circle.radius, circle.radius)));
        }

        return result;
    }

    public static pointToCicle(point: Vector2, circle: Circle){
        let result = new CollisionResult();

        let distanceSquared = Vector2.distanceSquared(point, circle.position);
        let sumOfRadii = 1 + circle.radius;
        let collided = distanceSquared < sumOfRadii * sumOfRadii;
        if (collided){
            result.normal = Vector2.normalize(Vector2.subtract(point, circle.position));
            let depth = sumOfRadii - Math.sqrt(distanceSquared);
            result.minimumTranslationVector = Vector2.multiply(new Vector2(-depth, -depth), result.normal);
            result.point = Vector2.add(circle.position, Vector2.multiply(result.normal, new Vector2(circle.radius, circle.radius)));

            return result;
        }

        return result;
    }

    public static closestPointOnLine(lineA: Vector2, lineB: Vector2, closestTo: Vector2){
        let v = Vector2.subtract(lineB, lineA);
        let w = Vector2.subtract(closestTo, lineA);
        let t = Vector2.dot(w, v) / Vector2.dot(v, v);
        t = MathHelper.clamp(t, 0, 1);

        return Vector2.add(lineA, Vector2.multiply(v, new Vector2(t, t)));
    }

    public static pointToPoly(point: Vector2, poly: Polygon){
        let result = new CollisionResult();

        if (poly.containsPoint(point)){
            let distanceSquared: number;
            let gpp = Polygon.getClosestPointOnPolygonToPoint(poly.points, Vector2.subtract(point, poly.position));
            let closestPoint = gpp.closestPoint;
            distanceSquared = gpp.distanceSquared;
            result.normal = gpp.edgeNormal;

            result.minimumTranslationVector = Vector2.multiply(result.normal, new Vector2(Math.sqrt(distanceSquared), Math.sqrt(distanceSquared)));
            result.point = Vector2.add(closestPoint, poly.position);

            return result;
        }

        return result;
    }
}