tracker/steamvr: fix formulae, pitch is/was broken

@KydDynoMyte said on reddit pitch goes +180 on yaw over 90.
It must be invalid matrix elements used in the call to atan2.

Replace with the version from April.

cf. https://www.reddit.com/r/Vive/comments/63qula/opentracks_almostdone_vive_support/dhrgh5l/?context=3

1 files changed, 3 insertions, 2 deletions

diff --git a/tracker-steamvr/steamvr.cpp b/tracker-steamvr/steamvr.cpp
index 3f0cd1d4..4cdec5e8 100644
--- a/tracker-steamvr/steamvr.cpp
+++ b/tracker-steamvr/steamvr.cpp
@@ -282,12 +282,13 @@ void steamvr::matrix_to_euler(double& yaw, double& pitch, double& roll, const vr
 {
     using std::atan2;
     using std::sqrt;
+    using std::asin;
 
     using d = double;
 
     yaw = atan2(d(result.m[2][0]), d(result.m[0][0]));
-    pitch = atan2(d(result.m[2][1]), d(result.m[2][2]));
-    roll = atan2(d(result.m[1][0]), d(result.m[0][0]));
+    pitch = atan2(-d(result.m[1][2]), d(result.m[1][1]));
+    roll = asin(d(result.m[1][0]));
 
     // TODO: gimbal lock avoidance?
 }