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using System;
using Microsoft.Xna.Framework;
namespace PlatformerStarterKit {
/// <summary>
/// A set of helpful methods for working with rectangles.
/// </summary>
public static class RectangleExtensions {
/// <summary>
/// Calculates the signed depth of intersection between two rectangles.
/// </summary>
/// <returns>
/// The amount of overlap between two intersecting rectangles. These
/// depth values can be negative depending on which wides the rectangles
/// intersect. This allows callers to determine the correct direction
/// to push objects in order to resolve collisions.
/// If the rectangles are not intersecting, Vector2.Zero is returned.
/// </returns>
public static Vector2 GetIntersectionDepth (this Rectangle rectA, Rectangle rectB) {
// Calculate half sizes.
float halfWidthA = rectA.Width / 2.0f;
float halfHeightA = rectA.Height / 2.0f;
float halfWidthB = rectB.Width / 2.0f;
float halfHeightB = rectB.Height / 2.0f;
// Calculate centers.
Vector2 centerA = new Vector2(rectA.Left + halfWidthA, rectA.Top + halfHeightA);
Vector2 centerB = new Vector2(rectB.Left + halfWidthB, rectB.Top + halfHeightB);
// Calculate current and minimum-non-intersecting distances between centers.
float distanceX = centerA.X - centerB.X;
float distanceY = centerA.Y - centerB.Y;
float minDistanceX = halfWidthA + halfWidthB;
float minDistanceY = halfHeightA + halfHeightB;
// If we are not intersecting at all, return (0, 0).
if (Math.Abs(distanceX) >= minDistanceX || Math.Abs(distanceY) >= minDistanceY)
return Vector2.Zero;
// Calculate and return intersection depths.
float depthX = distanceX > 0 ? minDistanceX - distanceX : -minDistanceX - distanceX;
float depthY = distanceY > 0 ? minDistanceY - distanceY : -minDistanceY - distanceY;
return new Vector2(depthX, depthY);
}
/// <summary>
/// Gets the position of the center of the bottom edge of the rectangle.
/// </summary>
public static Vector2 GetBottomCenter (this Rectangle rect) {
return new Vector2(rect.X + rect.Width / 2.0f, rect.Bottom);
}
}
}