/* RCSid $Id: pmapsrc.h,v 2.7 2020/08/07 01:21:13 rschregle Exp $ */

/* 
   ======================================================================
   Photon map support routines for emission from light sources

   Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
   (c) Fraunhofer Institute for Solar Energy Systems,
       supported by the German Research Foundation 
       (DFG LU-204/10-2, "Fassadenintegrierte Regelsysteme" (FARESYS)) 
   (c) Lucerne University of Applied Sciences and Arts,
       supported by the Swiss National Science Foundation 
       (SNSF #147053, "Daylight Redirecting Components")
   (c) Tokyo University of Science,
       supported by the JSPS Grants-in-Aid for Scientific Research 
       (KAKENHI JP19KK0115, "Three-Dimensional Light Flow")
   ======================================================================
   
   $Id: pmapsrc.h,v 2.7 2020/08/07 01:21:13 rschregle Exp $
*/



#ifndef PMAPSRC_H
   #define PMAPSRC_H

   #include "ray.h"
   #include "source.h"



   /* Data structures for photon emission */
   typedef struct {
      unsigned theta, phi;               /* Direction indices */
      COLOR pdf;                         /* Probability of emission in this
                                            direction per RGB */
      float cdf;                         /* Cumulative probability up to
                                            this sample */
   } EmissionSample;

   typedef struct {
      unsigned numTheta, numPhi;         /* Num divisions in theta & phi */
      double dCosTheta, dPhi;            /* Increments for above */
      RREAL cosThetaMax;                 /* cos(source aperture) */
      FVECT uh, vh, wh;                  /* Emission aperture axes at origin, 
                                            w is normal*/
      FVECT us, vs, ws;                  /* Source surface axes at origin, 
                                            w is normal */
      FVECT photonOrg;                   /* Current photon origin */
      EmissionSample *samples;           /* PDF samples for photon emission 
                                            directions */
      unsigned long numPartitions;       /* Number of surface partitions */
      RREAL partArea;                    /* Area covered by each partition */
      SRCREC *src, *port;                /* Current source and port */
      unsigned long partitionCnt,        /* Current surface partition */
                    maxPartitions,       /* Max allocated partitions */
                    numSamples;          /* Number of PDF samples */
      unsigned char* partitions;         /* Source surface partitions */
      COLOR partFlux;                    /* Total flux emitted by partition */
      float cdf;                         /* Cumulative probability */
   } EmissionMap;


   
   /* Photon port flags (orientation relative to surface normal):
    * Forward, backward, both (bidirectional). */
   #define PMAP_PORTFWD 1
   #define PMAP_PORTBWD 2
   #define PMAP_PORTBI  (PMAP_PORTFWD | PMAP_PORTBWD)
   

   /* Photon ports for emission from geometry en lieu of light sources */
   extern char *photonPortList [MAXSET + 1];
   extern SRCREC *photonPorts;
   extern unsigned numPhotonPorts;

   /* Dispatch tables for partitioning light source surfaces and generating
      an origin for photon emission */
   extern void (*photonPartition []) (EmissionMap*);
   extern void (*photonOrigin []) (EmissionMap*);



   void getPhotonPorts (char **portList);
   /* Find geometry declared as photon ports from modifiers in portList */

   void initPhotonEmissionFuncs ();
   /* Init photonPartition[] and photonOrigin[] dispatch tables with source
      specific emission routines */

   void initPhotonEmission (EmissionMap *emap, float numPdfSamples);
   /* Initialize photon emission from partitioned light source emap -> src;
    * this involves integrating the flux emitted from the current photon
    * origin emap -> photonOrg and setting up a PDF to sample the emission
    * distribution with numPdfSamples samples */

   void emitPhoton (const EmissionMap*, RAY* ray);
   /* Emit photon from current source partition based on emission 
      distribution and return new photon ray */

   void multDirectPmap (RAY *r);
   /* Factor irradiance from direct photons into r -> rcol; interface to
    * direct() */

   void inscatterVolumePmap (RAY *r, COLOR inscatter);
   /* Add inscattering from volume photon map; interface to srcscatter() */

#endif