Fix T44102: Mirrored objects render black with Blender Internal and Autosmooth.

Normals are not vertices, we cannot apply matrix's scale to them...

source/blender/render/intern/source/convertblender.c

@@ -577,6 +577,17 @@ static void autosmooth(Render *UNUSED(re), ObjectRen *obr, float mat[4][4], shor
 	VlakRen *vlr;
 	int a, totvert;
 
+	float rot[3][3];
+
+	/* Note: For normals, we only want rotation, not scaling component.
+	 *       Negative scales (aka mirroring) give wrong results, see T44102. */
+	if (lnors) {
+		float mat3[3][3], size[3];
+
+		copy_m3_m4(mat3, mat);
+		mat3_to_rot_size(rot, size, mat3);
+	}
+
 	if (obr->totvert == 0)
 		return;
 
@@ -611,9 +622,8 @@ static void autosmooth(Render *UNUSED(re), ObjectRen *obr, float mat[4][4], shor
 		ver = RE_findOrAddVert(obr, a);
 		mul_m4_v3(mat, ver->co);
 		if (lnors) {
-			mul_mat3_m4_v3(mat, ver->n);
+			mul_m3_v3(rot, ver->n);
 			negate_v3(ver->n);
-			normalize_v3(ver->n);
 		}
 	}
 	for (a = 0; a < obr->totvlak; a++) {