ProceduralTextureHandler

typedef struct st_LWTextureHandler {
   LWInstanceFuncs *inst;
   LWItemFuncs     *item;
   LWRenderFuncs   *rend;
   double          (*evaluate) (LWInstance, LWTextureAccess *);
   unsigned int    (*flags)    (LWInstance);
} LWTextureHandler;

LWTEXF_GRAD      1
LWTEXF_SLOWPREVIEW  2
LWTEXF_AXIS      4
LWTEXF_AALIAS       8

LWTXEF_VECTOR      (1<<0)
LWTXEF_AXISX    (1<<1)
LWTXEF_AXISY    (1<<2)
LWTXEF_AXISZ    (1<<3)

typedef struct st_LWTextureAccess {
   double pos[3];
   double spotSize;
   double txGrad[3];
   int    flags;
} LWTextureAccess;