From e76a5b1d3da256f7952146147891cf6a89546315 Mon Sep 17 00:00:00 2001
From: Lubos <tridosm@gmail.com>
Date: Fri, 10 May 2024 19:40:13 +0200
Subject: [PATCH] OpenXR - Gran Turismo projection hack

---
 Common/VR/PPSSPPVR.cpp |  4 +++-
 Core/Compatibility.cpp |  1 +
 Core/Compatibility.h   |  1 +
 assets/compatvr.ini    | 11 +++++++++++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Common/VR/PPSSPPVR.cpp b/Common/VR/PPSSPPVR.cpp
index b16a57a9c7..a3a735d10c 100644
--- a/Common/VR/PPSSPPVR.cpp
+++ b/Common/VR/PPSSPPVR.cpp
@@ -811,7 +811,9 @@ void UpdateVRParams(float* projMatrix) {
 void UpdateVRProjection(float* projMatrix, float* leftEye, float* rightEye) {
 	float output[16];
 	for (int i = 0; i < 16; i++) {
-		if (fabs(projMatrix[i]) > 0) {
+		if (PSP_CoreParameter().compat.vrCompat().ProjectionHack && ((i == 8) || (i == 9))) {
+			output[i] = 0;
+		} else if (fabs(projMatrix[i]) > 0) {
 			output[i] = vrMatrix[VR_PROJECTION_MATRIX][i];
 			if ((output[i] > 0) != (projMatrix[i] > 0)) {
 				output[i] *= -1.0f;
diff --git a/Core/Compatibility.cpp b/Core/Compatibility.cpp
index 6494760a24..bbc1e34c42 100644
--- a/Core/Compatibility.cpp
+++ b/Core/Compatibility.cpp
@@ -145,6 +145,7 @@ void Compatibility::CheckVRSettings(IniFile &iniFile, const std::string &gameID)
 	CheckSetting(iniFile, gameID, "ForceMono", &vrCompat_.ForceMono);
 	CheckSetting(iniFile, gameID, "IdentityViewHack", &vrCompat_.IdentityViewHack);
 	CheckSetting(iniFile, gameID, "MirroringVariant", &vrCompat_.MirroringVariant);
+	CheckSetting(iniFile, gameID, "ProjectionHack", &vrCompat_.ProjectionHack);
 	CheckSetting(iniFile, gameID, "Skyplane", &vrCompat_.Skyplane);
 	CheckSetting(iniFile, gameID, "UnitsPerMeter", &vrCompat_.UnitsPerMeter);
 
diff --git a/Core/Compatibility.h b/Core/Compatibility.h
index 1739112d36..82cbabbf4f 100644
--- a/Core/Compatibility.h
+++ b/Core/Compatibility.h
@@ -115,6 +115,7 @@ struct VRCompat {
 	bool ForceFlatScreen;
 	bool IdentityViewHack;
 	int MirroringVariant;
+	bool ProjectionHack;
 	bool Skyplane;
 	float UnitsPerMeter;
 };
diff --git a/assets/compatvr.ini b/assets/compatvr.ini
index 84fac0d978..e05251c5a5 100644
--- a/assets/compatvr.ini
+++ b/assets/compatvr.ini
@@ -110,6 +110,17 @@ ULES00035 = 3
 ULUS10014 = 3
 
 
+[ProjectionHack]
+# Forces ignoring of projection matrix pivot point.
+
+# Gran Turismo: The Real Driving Simulator
+NPJG00027 = true
+UCAS40265 = true
+UCES01245 = true
+UCJS10100 = true
+UCUS98632 = true
+
+
 [Skyplane]
 # Workaround to remove the background skyplane and add clearing framebuffer with a fog color.