From ddbd87e2a1af1b0f4a13c3c91acb558193cd8494 Mon Sep 17 00:00:00 2001
From: Sam Hellawell <sshellawell@gmail.com>
Date: Thu, 4 Jul 2024 03:12:06 +0100
Subject: [PATCH] Fix blending with additional offsets (sneaking issue)

---
 apps/openmw/mwrender/animblendcontroller.cpp | 24 +++++++++++++++++++-
 apps/openmw/mwrender/rotatecontroller.hpp    | 10 ++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/apps/openmw/mwrender/animblendcontroller.cpp b/apps/openmw/mwrender/animblendcontroller.cpp
index 412c83d89a..8c40cd441b 100644
--- a/apps/openmw/mwrender/animblendcontroller.cpp
+++ b/apps/openmw/mwrender/animblendcontroller.cpp
@@ -1,4 +1,5 @@
 #include "animblendcontroller.hpp"
+#include "rotatecontroller.hpp"
 
 #include <components/debug/debuglog.hpp>
 
@@ -308,10 +309,31 @@ namespace MWRender
         {
             mBlendTrigger = false;
             mBlendStartTime = time;
-            // Nif mRotation is used here because it's unaffected by the side-effects of RotationController
+
+            // Nif mRotationScale is used here because it's unaffected by the side-effects of RotationController
             mBlendStartRot = node->mRotationScale.toOsgMatrix().getRotate();
             mBlendStartTrans = node->getMatrix().getTrans();
             mBlendStartScale = node->mScale;
+
+            // Subtract any rotate controller's offset from start transform (if it appears after this callback)
+            // this is required otherwise the blend start will be with an offset, then offset could be applied again
+            // fixes an issue with camera jumping during first person sneak jumping camera
+            osg::Callback* updateCb = node->getUpdateCallback()->getNestedCallback();
+            while (updateCb)
+            {
+                MWRender::RotateController* rotateController = dynamic_cast<MWRender::RotateController*>(updateCb);
+                if (rotateController)
+                {
+                    const osg::Quat rotate = rotateController->getRotate();
+                    const osg::Vec3f offset = rotateController->getOffset();
+                    const osg::Quat worldOrient = rotateController->getWorldOrientation(node) * rotate.inverse();
+                    const osg::Quat worldOrientInverse = worldOrient.inverse();
+
+                    mBlendStartTrans -= worldOrientInverse * offset;
+                }
+
+                updateCb = updateCb->getNestedCallback();
+            }
         }
 
         calculateInterpFactor(time);
diff --git a/apps/openmw/mwrender/rotatecontroller.hpp b/apps/openmw/mwrender/rotatecontroller.hpp
index 3c7e130d98..143585d039 100644
--- a/apps/openmw/mwrender/rotatecontroller.hpp
+++ b/apps/openmw/mwrender/rotatecontroller.hpp
@@ -20,10 +20,20 @@ namespace MWRender
     public:
         RotateController(osg::Node* relativeTo);
 
+        osg::Quat getWorldOrientation(osg::Node* node);
+
         void setEnabled(bool enabled);
         void setOffset(const osg::Vec3f& offset);
         void setRotate(const osg::Quat& rotate);
 
+        const osg::Vec3f getOffset() const {
+            return mOffset;
+        }
+
+        const osg::Quat getRotate() const {
+            return mRotate;
+        }
+
         void operator()(osg::MatrixTransform* node, osg::NodeVisitor* nv);
 
     protected: