Cleanup involves releasing the memory used by texture resources when those resources are no longer needed.
Function: PEXExtFreeTM (optional). Free a texture map resource.
Function: PEXExtFreeTMDescription (optional). Free a texture map description resource.
PEXExtTextureMap texture_map; /* Texture resource to free; created using PEXExtCreateTM. */
PEXExtTMDescription tm_description; /* Texture description resource to free; created using PEXExtCreateTMDescription. */