From dd3ec18204143d192f269503623c4ffcc4356e42 Mon Sep 17 00:00:00 2001
From: Ada <ada@thingvellir.net>
Date: Sun, 26 Jan 2025 00:35:17 +1000
Subject: [PATCH] DeferredFrameTransform: Hack to get lighting working properly
 in VR

Somewhere, the eye view transform is being applied twice. For now,
this hack with applying an inverse view transform corrects the bugged
lighting in the XR branch.
---
 .../src/DeferredFrameTransform.cpp            |  4 +++-
 plugins/openxr/src/OpenXrContext.cpp          | 20 -------------------
 plugins/openxr/src/OpenXrContext.h            |  2 --
 3 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/libraries/render-utils/src/DeferredFrameTransform.cpp b/libraries/render-utils/src/DeferredFrameTransform.cpp
index 21d5b120d6..7a5a14c459 100644
--- a/libraries/render-utils/src/DeferredFrameTransform.cpp
+++ b/libraries/render-utils/src/DeferredFrameTransform.cpp
@@ -67,7 +67,9 @@ void DeferredFrameTransform::update(RenderArgs* args, glm::vec2 jitter) {
 
         for (int i = 0; i < 2; i++) {
             // Compose the mono Eye space to Stereo clip space Projection Matrix
-            auto sideViewMat = projMats[i] * eyeViews[i];
+            // FIXME: eyeViews is being applied twice somewhere,
+            // this glm::inverse call undoes the bugged transform
+            auto sideViewMat = projMats[i] * glm::inverse(eyeViews[i]);
             frameTransformBuffer.projectionUnjittered[i] = sideViewMat;
             frameTransformBuffer.invProjectionUnjittered[i] = glm::inverse(sideViewMat);
 
diff --git a/plugins/openxr/src/OpenXrContext.cpp b/plugins/openxr/src/OpenXrContext.cpp
index 9fc1d282dd..e29649f0a4 100644
--- a/plugins/openxr/src/OpenXrContext.cpp
+++ b/plugins/openxr/src/OpenXrContext.cpp
@@ -89,7 +89,6 @@ bool OpenXrContext::initInstance() {
         return false;
 
     bool openglSupported = false;
-    bool bindingModificationSupported = false;
 
     qCInfo(xr_context_cat, "Runtime supports %d extensions:", count);
     for (uint32_t i = 0; i < count; i++) {
@@ -97,18 +96,6 @@ bool OpenXrContext::initInstance() {
         if (strcmp(XR_KHR_OPENGL_ENABLE_EXTENSION_NAME, properties[i].extensionName) == 0) {
             openglSupported = true;
         }
-
-        if (strcmp(XR_KHR_BINDING_MODIFICATION_EXTENSION_NAME, properties[i].extensionName) == 0) {
-            bindingModificationSupported = true;
-        }
-
-        if (strcmp(XR_EXT_DPAD_BINDING_EXTENSION_NAME, properties[i].extensionName) == 0) {
-            _dpadBindingSupported = true;
-        }
-
-        if (strcmp(XR_EXT_PALM_POSE_EXTENSION_NAME, properties[i].extensionName) == 0) {
-            _palmPoseSupported = true;
-        }
     }
 
     if (!openglSupported) {
@@ -117,13 +104,6 @@ bool OpenXrContext::initInstance() {
     }
 
     std::vector<const char*> enabled = {XR_KHR_OPENGL_ENABLE_EXTENSION_NAME};
-    if (bindingModificationSupported && _dpadBindingSupported) {
-        enabled.emplace(enabled.end(), XR_KHR_BINDING_MODIFICATION_EXTENSION_NAME);
-        enabled.emplace(enabled.end(), XR_EXT_DPAD_BINDING_EXTENSION_NAME);
-    }
-    if (_palmPoseSupported) {
-        enabled.emplace(enabled.end(), XR_EXT_PALM_POSE_EXTENSION_NAME);
-    }
 
     XrInstanceCreateInfo info = {
       .type = XR_TYPE_INSTANCE_CREATE_INFO,
diff --git a/plugins/openxr/src/OpenXrContext.h b/plugins/openxr/src/OpenXrContext.h
index 225e5509fe..025682a101 100644
--- a/plugins/openxr/src/OpenXrContext.h
+++ b/plugins/openxr/src/OpenXrContext.h
@@ -69,8 +69,6 @@ public:
     QString _systemName;
     bool _isSessionRunning = false;
 
-    bool _dpadBindingSupported = false;
-    bool _palmPoseSupported = false;
     bool _dpadNeedsClick = false;
 
 private: