Center shape according to logic Bullet applies

1 files changed, 38 insertions, 20 deletions

diff --git a/scene/resources/height_map_shape.cpp b/scene/resources/height_map_shape.cpp
index 32e9c527ef..98b597ac0a 100644
--- a/scene/resources/height_map_shape.cpp
+++ b/scene/resources/height_map_shape.cpp
@@ -34,35 +34,53 @@
 Vector<Vector3> HeightMapShape::_gen_debug_mesh_lines() {
 	Vector<Vector3> points;
 
-	// This will be slow for large maps...
-	// also we'll have to figure out how well bullet centers this shape...
+	if ((map_width != 0) && (map_depth != 0)) {
 
-	Vector2 size(map_width - 1, map_depth - 1);
-	Vector2 start = size * -0.5;
-	int offset = 0;
+		// This will be slow for large maps...
+		// also we'll have to figure out how well bullet centers this shape...
 
-	PoolRealArray::Read r = map_data.read();
+		Vector2 size(map_width - 1, map_depth - 1);
+		Vector2 start = size * -0.5;
 
-	for (int d = 0; d < map_depth; d++) {
-		Vector3 height(start.x, 0.0, start.y);
+		PoolRealArray::Read r = map_data.read();
 
-		for (int w = 0; w < map_width; w++) {
-			height.y = r[offset++];
+		// Bullet centers our heightmap, this is really counter intuitive but for now we'll adjust our debug shape accordingly:
+		// https://github.com/bulletphysics/bullet3/blob/master/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h#L33
+		float min = r[0];
+		float max = r[0];
+		for (int i = 0; i < map_data.size(); i++) {
+			if (min > r[i]) min = r[i];
+			if (max < r[i]) max = r[i];
+		};
+		float center = min + ((max - min) * 0.5);
 
-			if (w != map_width - 1) {
-				points.push_back(height);
-				points.push_back(Vector3(height.x + 1.0, r[offset], height.z));
-			}
+		// reserve some memory for our points..
+		points.resize(((map_width - 1) * map_depth * 2) + (map_width * (map_depth - 1) * 2));
+
+		// now set our points
+		int r_offset = 0;
+		int w_offset = 0;
+		for (int d = 0; d < map_depth; d++) {
+			Vector3 height(start.x, 0.0, start.y);
+
+			for (int w = 0; w < map_width; w++) {
+				height.y = r[r_offset++] - center;
 
-			if (d != map_depth - 1) {
-				points.push_back(height);
-				points.push_back(Vector3(height.x, r[offset + map_width - 1], height.z + 1.0));
+				if (w != map_width - 1) {
+					points.write[w_offset++] = height;
+					points.write[w_offset++] = Vector3(height.x + 1.0, r[r_offset] - center, height.z);
+				}
+
+				if (d != map_depth - 1) {
+					points.write[w_offset++] = height;
+					points.write[w_offset++] = Vector3(height.x, r[r_offset + map_width - 1] - center, height.z + 1.0);
+				}
+
+				height.x += 1.0;
 			}
 
-			height.x += 1.0;
+			start.y += 1.0;
 		}
-
-		start.y += 1.0;
 	}
 
 	return points;