From 4cdaa6e3dfc48a90dd1d5f21ed52bb6ae8d12fb4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joachim=20Sch=C3=B6berl?= <joachim.schoeberl@tuwien.ac.at>
Date: Fri, 16 Oct 2020 10:54:34 +0200
Subject: [PATCH] differentiate 1 correctly

---
 libsrc/csg/polyhedra.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libsrc/csg/polyhedra.cpp b/libsrc/csg/polyhedra.cpp
index c123458b..ae9e53bd 100644
--- a/libsrc/csg/polyhedra.cpp
+++ b/libsrc/csg/polyhedra.cpp
@@ -281,7 +281,7 @@ namespace netgen
                       *testout << "tang in plane" << endl;
                     double dlam1 = face.w1 * v;
                     double dlam2 = face.w2 * v;
-                    double dlam3 = 1-dlam1-dlam2;
+                    double dlam3 = -dlam1-dlam2;
                     if (printing)
                       *testout << "dlam = " << dlam1 << " " << dlam2 << " " << dlam3 << endl;
                     bool in1 = lam1 > eps_base1 || dlam1 > -eps_base1;