From 82279538a3e24b6f5bf5b72c56bb37a60640fc05 Mon Sep 17 00:00:00 2001
From: Morris Tabor <80684659+mortarroad@users.noreply.github.com>
Date: Fri, 20 Aug 2021 15:18:55 +0200
Subject: [PATCH] Fix winding of new convex hull implementation.

---
 core/math/convex_hull.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/core/math/convex_hull.cpp b/core/math/convex_hull.cpp
index 85fafa47b48..85ab7b9f007 100644
--- a/core/math/convex_hull.cpp
+++ b/core/math/convex_hull.cpp
@@ -2286,9 +2286,18 @@ Error ConvexHullComputer::convex_hull(const Vector3 *p_points, int32_t p_point_c
 			e = e->get_next_edge_of_face();
 		} while (e != e_start);
 
+		// reverse indices: Godot wants clockwise, but this is counter-clockwise
+		if (face.indices.size() > 2) {
+			// reverse all but the first index.
+			int *indices = face.indices.ptrw();
+			for (int c = 0; c < (face.indices.size() - 1) / 2; c++) {
+				SWAP(indices[c + 1], indices[face.indices.size() - 1 - c]);
+			}
+		}
+
 		// compute normal
 		if (face.indices.size() >= 3) {
-			face.plane = Plane(r_mesh.vertices[face.indices[0]], r_mesh.vertices[face.indices[2]], r_mesh.vertices[face.indices[1]]);
+			face.plane = Plane(r_mesh.vertices[face.indices[0]], r_mesh.vertices[face.indices[1]], r_mesh.vertices[face.indices[2]]);
 		} else {
 			WARN_PRINT("Too few vertices per face.");
 		}