From b32f5a922f05989ff129c3d266ebbed14b751e2a Mon Sep 17 00:00:00 2001
From: Brecht Van Lommel <brecht@blender.org>
Date: Wed, 15 Dec 2021 20:25:41 +0100
Subject: Fix T93995: Cycles camera motion blur not working in right stereo
 view

Thanks to Michael (michael64) for identifying the solution.

Ref D13567
---
 intern/cycles/blender/session.cpp | 7 +++++++
 intern/cycles/blender/sync.cpp    | 5 +++++
 intern/cycles/blender/sync.h      | 3 ++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/intern/cycles/blender/session.cpp b/intern/cycles/blender/session.cpp
index b8165186b4f..b6f72707fe0 100644
--- a/intern/cycles/blender/session.cpp
+++ b/intern/cycles/blender/session.cpp
@@ -396,6 +396,13 @@ void BlenderSession::render(BL::Depsgraph &b_depsgraph_)
     /* set the current view */
     b_engine.active_view_set(b_rview_name.c_str());
 
+    /* Force update in this case, since the camera transform on each frame changes
+     * in different views. This could be optimized by somehow storing the animated
+     * camera transforms separate from the fixed stereo transform. */
+    if ((scene->need_motion() != Scene::MOTION_NONE) && view_index > 0) {
+      sync->tag_update();
+    }
+
     /* update scene */
     BL::Object b_camera_override(b_engine.camera_override());
     sync->sync_camera(b_render, b_camera_override, width, height, b_rview_name.c_str());
diff --git a/intern/cycles/blender/sync.cpp b/intern/cycles/blender/sync.cpp
index 949b7cb1b3b..56137374d8e 100644
--- a/intern/cycles/blender/sync.cpp
+++ b/intern/cycles/blender/sync.cpp
@@ -95,6 +95,11 @@ void BlenderSync::reset(BL::BlendData &b_data, BL::Scene &b_scene)
   this->b_scene = b_scene;
 }
 
+void BlenderSync::tag_update()
+{
+  has_updates_ = true;
+}
+
 /* Sync */
 
 void BlenderSync::sync_recalc(BL::Depsgraph &b_depsgraph, BL::SpaceView3D &b_v3d)
diff --git a/intern/cycles/blender/sync.h b/intern/cycles/blender/sync.h
index 98197564bec..2db4125ba1c 100644
--- a/intern/cycles/blender/sync.h
+++ b/intern/cycles/blender/sync.h
@@ -66,6 +66,8 @@ class BlenderSync {
 
   void reset(BL::BlendData &b_data, BL::Scene &b_scene);
 
+  void tag_update();
+
   /* sync */
   void sync_recalc(BL::Depsgraph &b_depsgraph, BL::SpaceView3D &b_v3d);
   void sync_data(BL::RenderSettings &b_render,
@@ -267,7 +269,6 @@ class BlenderSync {
 
   Progress &progress;
 
- protected:
   /* Indicates that `sync_recalc()` detected changes in the scene.
    * If this flag is false then the data is considered to be up-to-date and will not be
    * synchronized at all. */
-- 
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