Platformer2D/Platformer2D.Core/Game/RectangleExtensions.cs

   1 #region File Description
   2 //-----------------------------------------------------------------------------
   3 // RectangleExtensions.cs
   4 //
   5 // Microsoft XNA Community Game Platform
   6 // Copyright (C) Microsoft Corporation. All rights reserved.
   7 //-----------------------------------------------------------------------------
   8 #endregion
   9
  10 using System;
  11 using Microsoft.Xna.Framework;
  12
  13 namespace Platformer2D
  14 {
  15     /// <summary>
  16     /// A set of helpful methods for working with rectangles.
  17     /// </summary>
  18     public static class RectangleExtensions
  19     {
  20         /// <summary>
  21         /// Calculates the signed depth of intersection between two rectangles.
  22         /// </summary>
  23         /// <returns>
  24         /// The amount of overlap between two intersecting rectangles. These
  25         /// depth values can be negative depending on which wides the rectangles
  26         /// intersect. This allows callers to determine the correct direction
  27         /// to push objects in order to resolve collisions.
  28         /// If the rectangles are not intersecting, Vector2.Zero is returned.
  29         /// </returns>
  30         public static Vector2 GetIntersectionDepth(this Rectangle rectA, Rectangle rectB)
  31         {
  32             // Calculate half sizes.
  33             float halfWidthA = rectA.Width / 2.0f;
  34             float halfHeightA = rectA.Height / 2.0f;
  35             float halfWidthB = rectB.Width / 2.0f;
  36             float halfHeightB = rectB.Height / 2.0f;
  37
  38             // Calculate centers.
  39             Vector2 centerA = new Vector2(rectA.Left + halfWidthA, rectA.Top + halfHeightA);
  40             Vector2 centerB = new Vector2(rectB.Left + halfWidthB, rectB.Top + halfHeightB);
  41
  42             // Calculate current and minimum-non-intersecting distances between centers.
  43             float distanceX = centerA.X - centerB.X;
  44             float distanceY = centerA.Y - centerB.Y;
  45             float minDistanceX = halfWidthA + halfWidthB;
  46             float minDistanceY = halfHeightA + halfHeightB;
  47
  48             // If we are not intersecting at all, return (0, 0).
  49             if (Math.Abs(distanceX) >= minDistanceX || Math.Abs(distanceY) >= minDistanceY)
  50                 return Vector2.Zero;
  51
  52             // Calculate and return intersection depths.
  53             float depthX = distanceX > 0 ? minDistanceX - distanceX : -minDistanceX - distanceX;
  54             float depthY = distanceY > 0 ? minDistanceY - distanceY : -minDistanceY - distanceY;
  55             return new Vector2(depthX, depthY);
  56         }
  57
  58         /// <summary>
  59         /// Gets the position of the center of the bottom edge of the rectangle.
  60         /// </summary>
  61         public static Vector2 GetBottomCenter(this Rectangle rect)
  62         {
  63             return new Vector2(rect.X + rect.Width / 2.0f, rect.Bottom);
  64         }
  65     }
  66 }