From 2e8d2ed62681316389e226e71fd3c8b85d53fbd5 Mon Sep 17 00:00:00 2001
From: Christopher Bruns <cmbruns@rotatingpenguin.com>
Date: Tue, 20 Sep 2016 18:14:14 -0400
Subject: [PATCH] Implement vr_swap_eyes CVAR, now that side-by-side mode is
 mostly working.

---
 src/gl/stereo3d/gl_stereo3d.h           |  1 -
 src/gl/stereo3d/gl_stereo_cvars.cpp     |  3 +++
 src/gl/stereo3d/gl_stereo_leftright.cpp | 11 ++++++++---
 src/gl/stereo3d/gl_stereo_leftright.h   | 11 +++++++----
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/gl/stereo3d/gl_stereo3d.h b/src/gl/stereo3d/gl_stereo3d.h
index c55154e51..81a72874f 100644
--- a/src/gl/stereo3d/gl_stereo3d.h
+++ b/src/gl/stereo3d/gl_stereo3d.h
@@ -58,7 +58,6 @@ public:
 	virtual void GetViewShift(float yaw, float outViewShift[3]) const;
 	virtual void SetUp() const {};
 	virtual void TearDown() const {};
-	// virtual void EndDrawScene(sector_t * viewsector) const {GLRenderer->EndDrawScene(viewsector);};
 };
 
 
diff --git a/src/gl/stereo3d/gl_stereo_cvars.cpp b/src/gl/stereo3d/gl_stereo_cvars.cpp
index 0927829fc..c09a7a974 100644
--- a/src/gl/stereo3d/gl_stereo_cvars.cpp
+++ b/src/gl/stereo3d/gl_stereo_cvars.cpp
@@ -35,6 +35,9 @@
 // Set up 3D-specific console variables:
 CVAR(Int, vr_mode, 0, CVAR_GLOBALCONFIG)
 
+// switch left and right eye views
+CVAR(Bool, vr_swap_eyes, false, CVAR_GLOBALCONFIG)
+
 // For broadest GL compatibility, require user to explicitly enable quad-buffered stereo mode.
 // Setting vr_enable_quadbuffered_stereo does not automatically invoke quad-buffered stereo,
 // but makes it possible for subsequent "vr_mode 7" to invoke quad-buffered stereo
diff --git a/src/gl/stereo3d/gl_stereo_leftright.cpp b/src/gl/stereo3d/gl_stereo_leftright.cpp
index 1919e320f..f2b1ba3fc 100644
--- a/src/gl/stereo3d/gl_stereo_leftright.cpp
+++ b/src/gl/stereo3d/gl_stereo_leftright.cpp
@@ -37,6 +37,7 @@
 
 EXTERN_CVAR(Float, vr_screendist)
 EXTERN_CVAR(Float, vr_hunits_per_meter)
+EXTERN_CVAR(Bool, vr_swap_eyes)
 
 namespace s3d {
 
@@ -50,7 +51,7 @@ VSMatrix ShiftedEyePose::GetProjection(float fov, float aspectRatio, float fovRa
 	// For stereo 3D, use asymmetric frustum shift in projection matrix
 	// Q: shouldn't shift vary with roll angle, at least for desktop display?
 	// A: No. (lab) roll is not measured on desktop display (yet)
-	double frustumShift = zNear * shift / vr_screendist; // meters cancel, leaving doom units
+	double frustumShift = zNear * getShift() / vr_screendist; // meters cancel, leaving doom units
 	// double frustumShift = 0; // Turning off shift for debugging
 	double fH = zNear * tan(DEG2RAD(fov) / 2) / fovRatio;
 	double fW = fH * aspectRatio;
@@ -68,13 +69,17 @@ VSMatrix ShiftedEyePose::GetProjection(float fov, float aspectRatio, float fovRa
 /* virtual */
 void ShiftedEyePose::GetViewShift(float yaw, float outViewShift[3]) const
 {
-	float dx = -cos(DEG2RAD(yaw)) * vr_hunits_per_meter * shift;
-	float dy = sin(DEG2RAD(yaw)) * vr_hunits_per_meter * shift;
+	float dx = -cos(DEG2RAD(yaw)) * vr_hunits_per_meter * getShift();
+	float dy = sin(DEG2RAD(yaw)) * vr_hunits_per_meter * getShift();
 	outViewShift[0] = dx;
 	outViewShift[1] = dy;
 	outViewShift[2] = 0;
 }
 
+float ShiftedEyePose::getShift() const 
+{
+	return vr_swap_eyes ? -shift : shift;
+}
 
 /* static */
 const LeftEyeView& LeftEyeView::getInstance(float ipd)
diff --git a/src/gl/stereo3d/gl_stereo_leftright.h b/src/gl/stereo3d/gl_stereo_leftright.h
index 2070ff53a..9fa7b40bc 100644
--- a/src/gl/stereo3d/gl_stereo_leftright.h
+++ b/src/gl/stereo3d/gl_stereo_leftright.h
@@ -37,11 +37,14 @@ class ShiftedEyePose : public EyePose
 {
 public:
 	ShiftedEyePose(float shift) : shift(shift) {};
-	float getShift() const { return shift; }
-	void setShift(float shift) { this->shift = shift; }
+	float getShift() const;
 	virtual VSMatrix GetProjection(float fov, float aspectRatio, float fovRatio) const;
 	virtual void GetViewShift(float yaw, float outViewShift[3]) const;
+
 protected:
+	void setShift(float shift) { this->shift = shift; }
+
+private:
 	float shift;
 };
 
@@ -50,7 +53,7 @@ class LeftEyePose : public ShiftedEyePose
 {
 public:
 	LeftEyePose(float ipd) : ShiftedEyePose( float(-0.5) * ipd) {}
-	float getIpd() const { return float(-2.0)*getShift(); }
+	float getIpd() const { return float(fabs(2.0f*getShift())); }
 	void setIpd(float ipd) { setShift(float(-0.5)*ipd); }
 };
 
@@ -59,7 +62,7 @@ class RightEyePose : public ShiftedEyePose
 {
 public:
 	RightEyePose(float ipd) : ShiftedEyePose(float(+0.5)*ipd) {}
-	float getIpd() const { return float(+2.0)*shift; }
+	float getIpd() const { return float(fabs(2.0f*getShift())); }
 	void setIpd(float ipd) { setShift(float(+0.5)*ipd); }
 };