From 6b54752c2e1bb0fff2a1abbd5a04612355d5de49 Mon Sep 17 00:00:00 2001
From: Brecht Van Lommel <brechtvanlommel@gmail.com>
Date: Sun, 1 Dec 2013 15:05:03 +0100
Subject: [PATCH] Fix T37667: rotational difference driver target marked
 invalid even though valid.

---
 source/blender/blenkernel/intern/fcurve.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index a40d7401566..32098c67ca7 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -1148,6 +1148,10 @@ static float dvar_eval_rotDiff(ChannelDriver *driver, DriverVar *dvar)
 		/* stop here... */
 		return 0.0f;
 	}
+	else {
+		dtar1->flag &= ~DTAR_FLAG_INVALID;
+		dtar2->flag &= ~DTAR_FLAG_INVALID;
+	}
 	
 	/* use the final posed locations */
 	mat4_to_quat(q1, pchan->pose_mat);