[024] Circle Rect Collision

[024] Circle Rect Collision

[15h] Math about Circle & Rectangle Collisions

[Feb 23] 2h - Circle Rect Collision Study
[Feb 24] 7h - Circle Rect Collision Study
[Feb 25] 6h - Circle Rect Collision UI

Learned the collision math between Circle & Rectangle,
so I can add it to my flocking logic to avoid walls.

    var r: Rect2
    var c_pos: Vector2
    var c_radius: float

    # Circle Rectangle Bounce [stackoverflow.com/a/45373126]
        c_nearest.x = maxf(r.position.x, minf(c_pos.x, r.position.x + r.size.x)) # closest point in rectangle
        c_nearest.y = maxf(r.position.y, minf(c_pos.y, r.position.y + r.size.y))
        
        var distance: Vector2 = _circle_position - _nearest                     # nearest distance to circle center
        var normal: Vector2 = Vector2(-distance.y, distance.x)                  # normal vector

        var normal_angle: float = atan2(normal.y, normal.x)                     # normal in radians (3.1416)
        var incoming_angle: float = atan2(_circle_velocity.y, _circle_velocity.x) # circle velocity in radians

        var theta: float = normal_angle - incoming_angle
        _circle_velocity = _circle_velocity.rotate(2 * theta)                   # bounce velocity
        

    # 2D Geometry Library [youtu.be/QZFH7yrJ4H4]
        # Circle overlaps Rectangle
        var c_nearest: Vector2
        c_nearest.x = maxf(r.position.x, minf(c_pos.x, r.position.x + r.size.x))
        c_nearest.y = maxf(r.position.y, minf(c_pos.y, r.position.y + r.size.y))
        var c_distance: float = c_pos.distance_to(c_nearest)                    # (c_nearest - c_pos).length()
        
        if c_distance - c_radius < 0:
            # overlaps if distance is less than circle radius