/*** EVALUATING THE SCENE ALONG A RAY SEGMENT ***/

typedef 
  void (*seg_eval_proc_t) (
    pcode_proc_t *proc,   /* The function's pseudo-code */
    h3_point_t *plo,      /* Start of segment */
    h3_point_t *phi,      /* End of segment */
    void *regs,           /* Evaluation registers */
    void *stack,          /* Evaluation stack */
    IntervalPair *ip      /* Out: bounding trapezoid for function along segment */
  );
  
typedef struct {
    seg_eval_proc_t *eval_proc;
    void *regs;
    void *stack;
  } seg_eval_closure_t;
  
seg_eval_proc_t *irt_seg_eval_ia;
  
seg_eval_proc_t *irt_seg_eval_ia_diff;

seg_eval_proc_t *irt_seg_eval_aa;

/*** COMPUTING THE SURFACE NORMAL AT A HIT POINT ***/

typedef 
  void (*nrm_eval_proc_t) (
    pcode_proc_t *proc,   /* The function's pseudo-code */                        
    h3_point_t *hit, 	  /* Nominal hit point */                                  
    void *regs,		  /* Evaluation registers */                              
    void *stack,	  /* Evaluation stack */                                  
    r3_t *nrm		  /* Out: outgoing surface normal at $hit$. */
  );			  
  
typedef struct {
    nrm_eval_proc_t *eval_proc;
    void *regs;
    void *stack;
  } nrm_eval_closure_t;
  
nrm_eval_proc_t *irt_nrm_eval;