Split collision detection into two phases, horizontal and vertical

The whole function should probably be refactored at some point, possibly like therapy5's but that may be too complicated.

#14

1 files changed, 24 insertions, 1 deletions

@@ -57,9 +57,12 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
 
   vec2i mapBounds = map.getMapSize() * map.getTileSize();
 
+  // First check horizontal movement only.
+  vec2i horizMovement = { newLoc.x(), curLoc.y() };
+
   vec2i oldColUL = curLoc + sprite.collisionOffset;
   vec2i oldColDR = oldColUL + sprite.collisionSize;
-  vec2i newColUL = newLoc + sprite.collisionOffset;
+  vec2i newColUL = horizMovement + sprite.collisionOffset;
   vec2i newColDR = newColUL + sprite.collisionSize;
 
   vec2i oldTileUL = oldColUL / map.getTileSize();
@@ -154,6 +157,26 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
     }
   }
 
+  // For vertical movement, assume that the horizontal movement has already
+  // taken place (as long as it was not in fact blocked).
+  vec2i effectiveCurLoc = curLoc;
+  vec2i vertMovement = newLoc;
+  if (result.horiz.blocked) {
+    vertMovement.x() = curLoc.x();
+  } else {
+    effectiveCurLoc.x() = newLoc.x();
+  }
+
+  oldColUL = effectiveCurLoc + sprite.collisionOffset;
+  oldColDR = oldColUL + sprite.collisionSize;
+  newColUL = vertMovement + sprite.collisionOffset;
+  newColDR = newColUL + sprite.collisionSize;
+
+  oldTileUL = oldColUL / map.getTileSize();
+  newTileUL = newColUL / map.getTileSize();
+  oldTileDR = oldColDR / map.getTileSize();
+  newTileDR = newColDR / map.getTileSize();
+
   if (dirHasDir(dir, Direction::down)) {
     if (newTileDR.y() > oldTileDR.y() &&
         newColDR.y() < mapBounds.h()) {