Stencil shadows require models consisting of closed meshes. The meshes must have no holes, and no polygons must intersect each other or touch each other with their flat side. Otherwise rendering errors (dark lines projecting from the model to the shadow) can be visible. In a closed mesh, every edge is shared by exactly two triangles. If the model's mesh is not closed, create a closed mesh LOD model or shadow model for shadow casting. The MED mesh tester can be used for determining whether a mesh is closed or not.