Gumroad - 50 Modeling Issues from Hell in Blender http://gumroad.com/l/50-modeling-issues-from-hell 3D modeling is hard, sometimes...
Common 3D Modeling Problems in Blender
A subdivided object collapsing into a shapeless mess
Topology going haywire
Non-manifold geometry
Boolean ops ruin the topology
Some models just explode (due to an error in the modifier stack)
Bevels overshooting
Exported models are broken
Too many polygons to even move a vertex
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