How can I determine if an object hit the top of a tile rectangle in MonoGame? [duplicate]

Question

I've been implementing an AI system in my 2D game using MonoGame.

In some situations when a collision between two objects occurs, I need the NPC to move in different directions depending on the direction of the collision. With the simple Rectangle.Intersects method I can't handle this, because it only detects if two rectangles intersect and doesn't tell me how they intersect.

Basically I need to know if the top of the NPC rectangle collides with the bottom of a tile rectangle, and so on.

This question talks about something similar but I don't think there is CollisionDetection2D.BoundingRectangle in MonoGame.

Answer 1

There are several solution to your problem. The first solution i can think of is instead of using one rectangle you can use 4, or even 9+ if you need more detail. Put a top-left, top-right, bottom-left, bottom-right rectangle within your main rectangle. When you have the collision you currently have you can check on the more detailed rectangles and see where it collides.

Another option would be to check it manually. If you just want to know if the top of a rectangle intersects with the bottom of another you can use the default Rectangle properties (.Bottom, .Top, .Left, .Right) and check there positions manually.

if (intersect)
{
    if (Math.Abs(rec1.Top - rec2.Bottom) < rec2.height / 2)
    {
        //rec1 is intersecting in the bottom half of rec2.
    }
}