some basic, not-quite-perfect, collision detection

GitOrigin-RevId: 32ba9d7687

Jumpy.Shared/Player.cs

@@ -8,7 +8,7 @@ namespace Jumpy {
   class Player {
     enum Facing { Left, Right };
     enum Pose { Walking, Standing, Crouching, Stretching, SwordSwing, Jumping };
-    enum AirState { Jumping, Ground };
+    enum AirState { Jumping, Ground, Falling };
 
     private Texture2D texture;
     private const int spriteSize = 48;
@@ -17,9 +17,9 @@ namespace Jumpy {
     private const int moveSpeed = 200;
     private const int jumpSpeed = 600;
     private const int gravity = 2000;
-    private const int groundLevel = Camera.Height - spriteSize / 2 + bottomPadding - 32;
+    private const int groundLevel = 10000;
 
-    private Point position = new Point(Camera.Width / 2, groundLevel);
+    private Point position = new Point(Camera.Width / 2, 10);
     private Facing facing = Facing.Right;
     private Pose pose = Pose.Standing;
     private AirState airState = AirState.Ground;
@@ -35,18 +35,55 @@ namespace Jumpy {
     // instead of complicated if-statements in this function.
     public void Update(
         GameTime time, History<GamePadState> gamePad, List<Rectangle> collisionTargets) {
+      Point oldPosition = position;
+      AirState oldAirState = airState;
       UpdateFromGamePad(time, gamePad);
 
-      Rectangle playerBbox =
-        new Rectangle(position.X - spriteWidth, position.Y - 9, spriteWidth * 2, 28);
-      Debug.AddRect(playerBbox, Color.Red);
+      bool someIntersection = false;
+
+      Rectangle playerBbox = new Rectangle(position.X - spriteWidth, position.Y - 8, spriteWidth * 2, 27);
+      bool standingOnGround = false;
       foreach (var rect in collisionTargets) {
+        playerBbox = new Rectangle(position.X - spriteWidth, position.Y - 8, spriteWidth * 2, 27);
+
         if (playerBbox.Intersects(rect)) {
+          someIntersection = true;
+          if (oldPosition.Y > position.Y) {
+            int diff = playerBbox.Top - rect.Bottom;
+            position.Y -= diff;
+            ySpeed *= 0.9;
+          } else {
+            airState = AirState.Ground;
+            int diff = playerBbox.Bottom - rect.Top;
+            position.Y -= diff;
+          }
           Debug.AddRect(rect, Color.Yellow);
         } else {
-          Debug.AddRect(rect, Color.Green);
+          playerBbox.Height += 1;
+          if (playerBbox.Intersects(rect)) {
+            standingOnGround = true;
+            Debug.AddRect(rect, Color.Cyan);
+          } else {
+            Debug.AddRect(rect, Color.Green);
+          }
         }
       }
+      if (oldAirState != AirState.Ground && standingOnGround) {
+        airState = AirState.Ground;
+        ySpeed = 0.0;
+      }
+      if (airState == AirState.Ground && !standingOnGround) {
+        airState = AirState.Falling;
+        ySpeed = 0.0;
+      }
+
+      if (airState == AirState.Ground) {
+        Debug.AddRect(playerBbox, Color.Red);
+      } else if (airState == AirState.Jumping) {
+        Debug.AddRect(playerBbox, Color.Orange);
+      } else {
+        Debug.AddRect(playerBbox, Color.Yellow);
+      }
     }
 
     void UpdateFromGamePad(GameTime time, History<GamePadState> gamePad) {
@@ -90,7 +127,7 @@ namespace Jumpy {
         pose = Pose.SwordSwing;
       }
 
-      if (airState == AirState.Jumping) {
+      if (airState == AirState.Jumping || airState == AirState.Falling) {
         position.Y += (int) (ySpeed * time.ElapsedGameTime.TotalSeconds);
         ySpeed += gravity * (float) time.ElapsedGameTime.TotalSeconds;
         if (position.Y > groundLevel) {