/* 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) 
       under the FARESYS project.
   (c) Lucerne University of Applied Sciences and Arts,
       supported by the Swiss National Science Foundation (SNSF #147053).
   (c) Tokyo University of Science,
       supported by the JSPS KAKENHI Grant Number JP19KK0115.
   ======================================================================
   
   $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 */
      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