Real time rendering

• Improve vertex cache locality
• Convert from right-handed to left-handed space
• Limit weights affecting a single vertex
• Split meshes to avoid exceeding bone count limits
• Triangulate arbitrary polygons
• Join identical vertices, optimize indexing
• Find degenerate polygons
• Split large meshes to overcome GPU limitations (i.e. vertex count)

Vertex data

• Compute "hard" per-face normal vectors
• Compute "smooth" per-vertex normal vectors
• Compute tangents and bitangents

Scenegraph

• Collapse the scene graph, transform everything to world coordinates
• Optimize meshes & nodes for fewer drawcalls

Other

• Validate the output structure to ensure maximum data integrity
• Remove unrequired materials, effectively detect and merge duplicates
• Try to correct face winding
• Drop dummy bones introduced somewhere in your content pipeline