From c96520583002062a6308b9cbded8c4fe907d25e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Salvador=20de=20la=20Puente=20Gonz=C3=A1lez?=
 <salva@unoyunodiez.com>
Date: Mon, 26 Feb 2018 13:16:38 +0100
Subject: [PATCH] Calculating transform parameters instead of overriding
 worldToCameraMatrix

---
 Assets/WebVR/Scripts/WebVRCamera.cs | 34 +++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/Assets/WebVR/Scripts/WebVRCamera.cs b/Assets/WebVR/Scripts/WebVRCamera.cs
index 9eaf398..c819de1 100755
--- a/Assets/WebVR/Scripts/WebVRCamera.cs
+++ b/Assets/WebVR/Scripts/WebVRCamera.cs
@@ -230,10 +230,11 @@ void Update()
 		}
 
 		if (active) {
-			cameraL.worldToCameraMatrix = clv * sitStand.inverse * transform.worldToLocalMatrix;
+			SetTransformFromViewMatrix (cameraL.transform, clv * sitStand.inverse * transform.worldToLocalMatrix);
 			cameraL.projectionMatrix = clp;
-			cameraR.worldToCameraMatrix = crv * sitStand.inverse * transform.worldToLocalMatrix;
+			SetTransformFromViewMatrix (cameraR.transform, crv * sitStand.inverse * transform.worldToLocalMatrix);
 			cameraR.projectionMatrix = crp;
+			SetHeadTransform ();
 		} else {
 			// apply left 
 			cameraMain.worldToCameraMatrix = clv * sitStand.inverse * transform.worldToLocalMatrix;
@@ -244,6 +245,35 @@ void Update()
 		#endif
 	}
 
+	// According to https://answers.unity.com/questions/402280/how-to-decompose-a-trs-matrix.html
+	private void SetTransformFromViewMatrix(Transform transform, Matrix4x4 webVRViewMatrix) {
+		Matrix4x4 trs = TransformViewMatrixToTRS(webVRViewMatrix);
+		transform.localPosition = trs.GetColumn(3);
+		transform.localRotation = Quaternion.LookRotation(trs.GetColumn(2), trs.GetColumn(1));
+		transform.localScale = new Vector3(
+			trs.GetColumn(0).magnitude,
+			trs.GetColumn(1).magnitude,
+			trs.GetColumn(2).magnitude
+        );
+    }
+
+	// According to https://forum.unity.com/threads/reproducing-cameras-worldtocameramatrix.365645/#post-2367177
+	private Matrix4x4 TransformViewMatrixToTRS(Matrix4x4 openGLViewMatrix) {
+		openGLViewMatrix.m20 *= -1;
+		openGLViewMatrix.m21 *= -1;
+		openGLViewMatrix.m22 *= -1;
+		openGLViewMatrix.m23 *= -1;  
+		return openGLViewMatrix.inverse;
+	}
+
+	private void SetHeadTransform() {
+		Transform leftTransform = cameraL.transform;
+		Transform rightTransform = cameraR.transform;
+		cameraMain.transform.localPosition = 
+			(rightTransform.localPosition - leftTransform.localPosition) / 2f + leftTransform.localPosition;
+		cameraMain.transform.localRotation = leftTransform.localRotation;
+		cameraMain.transform.localScale = leftTransform.localScale;
+	}
 	void OnGUI()
 	{
 		if (!showPerf)