simplify mapping from normalized device coordinates

flake.lock

@@ -103,11 +103,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1770843696,
-        "narHash": "sha256-LovWTGDwXhkfCOmbgLVA10bvsi/P8eDDpRudgk68HA8=",
+        "lastModified": 1771025653,
+        "narHash": "sha256-Y7FxD/qS8VRBQ7lgJIbMX7HU3FQifaMkJzOPz8NFrac=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "2343bbb58f99267223bc2aac4fc9ea301a155a16",
+        "rev": "7d2ae6d8b8b697b5114a4249d0d958ee5f23d8fe",
         "type": "github"
       },
       "original": {
@@ -142,11 +142,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1770865833,
-        "narHash": "sha256-oiARqnlvaW6pVGheVi4ye6voqCwhg5hCcGish2ZvQzI=",
+        "lastModified": 1771125043,
+        "narHash": "sha256-ldf/s49n6rOAxl7pYLJGGS1N/assoHkCOWdEdLyNZkc=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "c8cfbe26238638e2f3a2c0ae7e8d240f5e4ded85",
+        "rev": "4912f951a26dc8142b176be2c2ad834319dc06e8",
         "type": "github"
       },
       "original": {

src/main.cpp

@@ -202,8 +202,7 @@ auto manual_transform(Edge2Set &result, const Edge3Set &edges,
   };
 
   auto map = [&](const Vector2 &a) -> Vector2 {
-    return Vector2((a.x + 1.0) / 2.0 * WIDTH,
-                   (1.0 - (a.y + 1.0)) / 2.0 * HEIGHT + HEIGHT / 2.0);
+    return Vector2((1.0 + a.x) / 2.0 * WIDTH, (1.0 - a.y) * HEIGHT / 2.0);
   };
 
 #ifdef PARALLEL_TRANSFORM