From 2c427d594f37d47b469ffac514b6ecd247ad9305 Mon Sep 17 00:00:00 2001
From: Jishan Singh <ringmaker>
Date: Mon, 22 Mar 2021 16:55:37 +0100
Subject: Fix T83638: mirror modifier with mirror object renders wrong motion
 blur

In this case both the mirror object and object itself moving in time may
change the geometry and must be checked.

Differential Revision: https://developer.blender.org/D10757
---
 source/blender/blenkernel/intern/object.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'source')

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 704d6d1cf4f..76c96ec9603 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -4885,7 +4885,7 @@ static bool object_deforms_in_time(Object *object)
   return object_moves_in_time(object);
 }
 
-static bool constructive_modifier_is_deform_modified(ModifierData *md)
+static bool constructive_modifier_is_deform_modified(Object *ob, ModifierData *md)
 {
   /* TODO(sergey): Consider generalizing this a bit so all modifier logic
    * is concentrated in MOD_{modifier}.c file,
@@ -4900,7 +4900,8 @@ static bool constructive_modifier_is_deform_modified(ModifierData *md)
   }
   if (md->type == eModifierType_Mirror) {
     MirrorModifierData *mmd = (MirrorModifierData *)md;
-    return mmd->mirror_ob != NULL && object_moves_in_time(mmd->mirror_ob);
+    return mmd->mirror_ob != NULL &&
+           (object_moves_in_time(mmd->mirror_ob) || object_moves_in_time(ob));
   }
   if (md->type == eModifierType_Screw) {
     ScrewModifierData *smd = (ScrewModifierData *)md;
@@ -4984,7 +4985,7 @@ int BKE_object_is_deform_modified(Scene *scene, Object *ob)
     bool can_deform = mti->type == eModifierTypeType_OnlyDeform || is_modifier_animated;
 
     if (!can_deform) {
-      can_deform = constructive_modifier_is_deform_modified(md);
+      can_deform = constructive_modifier_is_deform_modified(ob, md);
     }
 
     if (can_deform) {
-- 
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