qardboard: Fix QardboardCamera following viewMatrix changes

Bonus: also remove the binding loop on the matrix property that was being
reported.

Change-Id: I2489a1f7ac5f65b4061ce069796d5afeab1811de
Reviewed-by: Mike Krus <mike.krus@kdab.com>

2 files changed, 30 insertions, 43 deletions

diff --git a/examples/qt3d/qardboard/QardboardCamera.qml b/examples/qt3d/qardboard/QardboardCamera.qml
index 1912b8a22..4832aeadc 100644
--- a/examples/qt3d/qardboard/QardboardCamera.qml
+++ b/examples/qt3d/qardboard/QardboardCamera.qml
@@ -50,6 +50,7 @@
 
 import Qt3D.Core 2.0
 import Qt3D.Render 2.0
+import Qardboard 1.0
 
 Entity {
     id: root
@@ -63,12 +64,17 @@ Entity {
     property vector3d position: Qt.vector3d(0.0, 0.0, 0.0)
     property vector3d viewDirection: Qt.vector3d(0.0, 0.0, 1.0)
     property vector3d viewUp: Qt.vector3d(0.0, 1.0, 0.0)
-    property alias viewMatrix: leftEyeTransform.matrix
+    property alias viewMatrix: eyeTransform.matrix
 
     readonly property real _fov2: Math.tan(fieldOfView * Math.PI / 180 * 0.5)
     readonly property real top: nearPlane * _fov2
     readonly property real a: aspectRatio * _fov2 * convergence
 
+    DeviceOrientation {
+        id: orientation
+        enabled: true
+    }
+
     CameraLens {
         id: leftEyeLens
         projectionType: CameraLens.FrustumProjection
@@ -92,33 +98,39 @@ Entity {
     }
 
     Transform {
-        id: leftEyeTransform
+        id: eyeTransform
+
+        function computeMatrix(roll, pitch, yaw) {
+            var n = Qt.matrix4x4()
+            n.rotate(-roll, Qt.vector3d(1, 0, 0))
+            n.rotate(yaw, Qt.vector3d(0, 1, 0))
+            var vd = n.times(stereoCamera.viewDirection)
+            var vu = n.times(stereoCamera.viewUp)
+            var vc = stereoCamera.position.minus(vd)
 
-        matrix: {
             var m = Qt.matrix4x4();
-            m.lookAt(root.position, root.position + root.viewDirection, root.viewUp);
-            return m;
+            m.translate(stereoCamera.position)
+            var zAxis = stereoCamera.position.minus(vc).normalized()
+            var xAxis = vu.crossProduct(zAxis).normalized();
+            var yAxis = zAxis.crossProduct(xAxis);
+            var r = Qt.matrix4x4(xAxis.x, yAxis.x, zAxis.x, 0,
+                                 xAxis.y, yAxis.y, zAxis.y, 0,
+                                 xAxis.z, yAxis.z, zAxis.z, 0,
+                                 0, 0, 0, 1)
+            return m.times(r);
         }
-    }
 
-    Transform {
-        id: rightEyeTransform
-
-        matrix: leftEyeTransform.matrix
+        matrix: computeMatrix(orientation.roll, orientation.pitch, orientation.yaw)
     }
 
+    components: [ eyeTransform ]
+
     property Entity leftCamera: Entity {
-        components: [
-            leftEyeLens,
-            leftEyeTransform
-        ]
+        components: [ leftEyeLens ]
     }
 
     property Entity rightCamera: Entity {
         id: rightCameraEntity
-        components: [
-            rightEyeLens,
-            rightEyeTransform
-        ]
+        components: [ rightEyeLens ]
     }
 }
diff --git a/examples/qt3d/qardboard/QardboardRootEntity.qml b/examples/qt3d/qardboard/QardboardRootEntity.qml
index 85e4fbc7e..004ebadc5 100644
--- a/examples/qt3d/qardboard/QardboardRootEntity.qml
+++ b/examples/qt3d/qardboard/QardboardRootEntity.qml
@@ -51,7 +51,6 @@
 import Qt3D.Core 2.0
 import Qt3D.Render 2.0
 import Qt3D.Input 2.0
-import Qardboard 1.0
 
 Entity {
     id: root
@@ -75,31 +74,7 @@ Entity {
         }
     ]
 
-    DeviceOrientation {
-        id: orientation
-        enabled: true
-    }
-
     QardboardCamera {
         id: stereoCamera
-        viewMatrix: computeMatrix(orientation.roll, orientation.pitch, orientation.yaw)
-
-        property vector3d vc
-        property vector3d vd
-        property vector3d vu
-
-        function computeMatrix(roll, pitch, yaw) {
-            var m = Qt.matrix4x4()
-            m.rotate(-roll, Qt.vector3d(1, 0, 0))
-            m.rotate(yaw, Qt.vector3d(0, 1, 0))
-            vd = m.times(stereoCamera.viewDirection)
-            vu = m.times(stereoCamera.viewUp)
-            var r = Qt.matrix4x4()
-            vc = stereoCamera.position.minus(vd)
-            r.lookAt(stereoCamera.position, vc, vu)
-//            console.log(roll.toFixed(2), pitch.toFixed(2), yaw.toFixed(2), stereoCamera.position, vd, vc, vu)
-//            console.log(r)
-            return r
-        }
     }
 }