add again gimbal lock workaround code

@KyokushinPL reports +-90 pitch boundary broken otherwise

1 files changed, 12 insertions, 0 deletions

diff --git a/opentrack/tracker.cpp b/opentrack/tracker.cpp
index 8892c85a..5b36971e 100644
--- a/opentrack/tracker.cpp
+++ b/opentrack/tracker.cpp
@@ -51,6 +51,18 @@ double Tracker::map(double pos, bool invertp, Mapping& axis)
 // http://stackoverflow.com/a/18436193
 static dmat<3, 1> rmat_to_euler(const dmat<3, 3>& R)
 {
+    static constexpr double pi = 3.141592653;
+    const double up = 90 * pi / 180.;
+    if (R(0, 2) > 0.998)
+    {
+        double roll = atan(R(1, 0) / R(2, 0));
+        return dmat<3, 1>({0., up, roll});
+    }
+    if (R(0, 2) < -0.998)
+    {
+        double roll = atan(R(1, 0) / R(2, 0));
+        return dmat<3, 1>({0., -up, roll});
+    }
     double pitch = asin(-R(0, 2));
     double roll = atan2(R(1, 2), R(2, 2));
     double yaw = atan2(R(0, 1), R(0, 0));