diff --git a/dev_notes/blender.md b/dev_notes/blender.md
index 4f94438e..35a642ea 100644
--- a/dev_notes/blender.md
+++ b/dev_notes/blender.md
@@ -748,5 +748,13 @@ f (8 4 2 6)//6
  - One very common bug we encounter is unexplainable wonky lighting
     - The issue typically comes down to normal management and can be solved with a few function calls or button clicks in Blender itself
 
+![](https://raw.githubusercontent.com/mebusy/notes/master/imgs/blender_cocentric_normal.png)
+
+The left side is a cube’s .obj file , which has been improperly given concentric normals.
+
+while the right side is correctly exported with planar normals. 
+
+
+
 
 
diff --git a/imgs/blender_cocentric_normal_render.png b/imgs/blender_cocentric_normal_render.png
new file mode 100644
index 00000000..3be5e26d
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diff --git a/imgs/blender_coplanar_render.png b/imgs/blender_coplanar_render.png
new file mode 100644
index 00000000..b37766c6
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