From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 3 Oct 2016 13:54:30 +0000 (+0300)
Subject: Reconstruct base camera object matrix with priority on up vector
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=b70741a6810b7fe822212dd6fa9110f674a47036;p=libs%2Fvr.git

Reconstruct base camera object matrix with priority on up vector

In VR it's imperative that the camera object matches reality and some
applications may have a non-horizontal look vector.  The up vector on
the other hand should always point up in the user's immediate frame of
reference.
---

diff --git a/source/headtrackingcamera.cpp b/source/headtrackingcamera.cpp
index 42eedd5..a296639 100644
--- a/source/headtrackingcamera.cpp
+++ b/source/headtrackingcamera.cpp
@@ -15,7 +15,14 @@ void HeadTrackingCamera::set_elevation_offset(float o)
 
 void HeadTrackingCamera::update_from_matrix(const GL::Matrix &hmd_matrix)
 {
-	GL::Matrix matrix = base_camera.get_object_matrix()*hmd_matrix;
+	const GL::Vector3 &up_dir = base_camera.get_up_direction();
+	GL::Vector3 right_dir = normalize(cross(base_camera.get_look_direction(), up_dir));
+	GL::Vector4 columns[4];
+	columns[0] = compose(right_dir, 0.0f);
+	columns[1] = compose(up_dir, 0.0f);
+	columns[2] = compose(cross(right_dir, up_dir), 0.0f);
+	columns[3] = compose(base_camera.get_position(), 1.0f);
+	GL::Matrix matrix = GL::Matrix::from_columns(columns)*hmd_matrix;
 
 	set_position(matrix*GL::Vector3()+base_camera.get_up_direction()*elevation_offset);
 	set_look_direction((matrix*GL::Vector4(0, 0, -1, 0)).slice<3>(0));