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/* RCSid $Id: bsdf.h,v 2.24 2016/03/06 01:13:17 schorsch Exp $ */
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/*
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* bsdf.h
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*
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* Declarations for bidirectional scattering distribution functions.
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* Assumes <stdio.h> already included.
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*
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* A material is oriented in right-hand coordinate system with X-axis
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* in the surface plane pointed to the right as seen from the front.
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* This means the Y-axis is "up" and the Z-axis is the surface normal.
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*
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* Note that we reverse the identification of "front" and "back" from
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* the conventions used in WINDOW 6. "Front" in our library points
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* in the +Z direction, towards the interior of the space rather
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* than the exterior.
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*
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* BSDF incident & exiting vectors are always oriented away from surface.
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*
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* Created by Greg Ward on 1/10/11.
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*
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*/
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#ifndef _BSDF_H_
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#define _BSDF_H_
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#include "fvect.h"
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#include "ccolor.h"
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#include "platform.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define SDnameLn 128 /* maximum BSDF name length */
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#define SDmaxCh 3 /* maximum # spectral channels */
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/* Component flags for SDsampBSDF() and SDdirectHemi() */
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#define SDsampR 0x1 /* include reflection */
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#define SDsampT 0x2 /* include transmission */
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#define SDsampS 0x3 /* include scattering (R+T) */
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#define SDsampSp 0x4 /* include non-diffuse portion */
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#define SDsampDf 0x8 /* include diffuse portion */
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#define SDsampSpR 0x5 /* include non-diffuse reflection */
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#define SDsampSpT 0x6 /* include non-diffuse transmission */
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#define SDsampSpS 0x7 /* include non-diffuse scattering */
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#define SDsampAll 0xF /* include everything */
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/* Projected solid angle query flags for SDsizeBSDF() */
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#define SDqueryVal 0x0 /* query single value */
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#define SDqueryMin 0x1 /* query minimum proj. solid angle */
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#define SDqueryMax 0x2 /* query maximum proj. solid angle */
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/* Error codes: normal return, out of memory, file i/o, file format, bad argument,
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bad data, unsupported feature, internal error, unknown error */
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typedef enum {SDEnone=0, SDEmemory, SDEfile, SDEformat, SDEargument,
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SDEdata, SDEsupport, SDEinternal, SDEunknown} SDError;
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/* English strings corresponding to ennumerated errors */
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extern const char *SDerrorEnglish[];
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/* Pointer to error list in preferred language */
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extern const char **SDerrorList;
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/* Additional information on last error (generally in English) */
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extern char SDerrorDetail[];
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/* Holder for BSDF value and spectral color */
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typedef struct {
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double cieY; /* photopic BSDF (Y) value */
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C_COLOR spec; /* spectral and (x,y) color */
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} SDValue;
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/* Cached, encoded, cumulative distribution for one incident (solid) angle */
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#define SD_CDIST_BASE(styp) double cTotal; \
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struct styp *next
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typedef struct SDCDst_s {
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SD_CDIST_BASE(SDCDst_s); /* base fields first */
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/* ...encoded distribution extends struct */
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} SDCDst;
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extern const SDCDst SDemptyCD; /* empty distribution */
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/* Forward declaration of BSDF component */
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typedef struct SDComp_s SDComponent;
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/* Methods needed to handle BSDF components (nothing is optional) */
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#ifdef __cplusplus
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/* in C++, the const puts the type into the local anonymous namespace,
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making it a private (and different) type for each file using this header.
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*/
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typedef struct {
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#else
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typedef const struct {
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#endif
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/* return non-diffuse BSDF */
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int (*getBSDFs)(float coef[SDmaxCh], const FVECT outVec,
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const FVECT inVec, SDComponent *sdc);
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/* query non-diffuse PSA for vector */
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SDError (*queryProjSA)(double *psa, const FVECT v1,
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const RREAL *v2, int qflags,
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SDComponent *sdc);
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/* get cumulative distribution */
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const SDCDst *(*getCDist)(const FVECT inVec, SDComponent *sdc);
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/* sample cumulative distribution */
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SDError (*sampCDist)(FVECT ioVec, double randX,
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const SDCDst *cdp);
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/* free a spectral BSDF component */
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void (*freeSC)(void *dist);
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} SDFunc;
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/* Structure to hold a spectral BSDF component (typedef SDComponent above) */
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struct SDComp_s {
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C_COLOR cspec[SDmaxCh]; /* component spectral bases */
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SDFunc *func; /* methods for this component */
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void *dist; /* loaded distribution data */
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SDCDst *cdList; /* cumulative distribution cache */
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};
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/* Container for non-diffuse BSDF components */
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typedef struct {
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double minProjSA; /* minimum projected solid angle */
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double maxHemi; /* maximum directional hemispherical */
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int ncomp; /* number of separate components */
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SDComponent comp[1]; /* BSDF components (extends struct) */
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} SDSpectralDF;
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/* Loaded BSDF data */
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typedef struct {
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char name[SDnameLn]; /* BSDF name (usu. derived from file) */
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char matn[SDnameLn]; /* material name */
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char makr[SDnameLn]; /* manufacturer */
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char *mgf; /* geometric description (if any) */
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double dim[3]; /* width, height, thickness (meters) */
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SDValue rLambFront; /* diffuse front reflectance */
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SDValue rLambBack; /* diffuse rear reflectance */
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SDValue tLamb; /* diffuse transmission */
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SDSpectralDF *rf, *rb; /* non-diffuse BRDF components */
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SDSpectralDF *tf, *tb; /* non-diffuse BTDF components */
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} SDData;
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/* List of loaded BSDFs */
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extern struct SDCache_s {
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SDData bsdf; /* BSDF data */
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unsigned refcnt; /* how many callers are using us? */
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struct SDCache_s /* next in cache list */
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*next;
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} *SDcacheList; /* Global BSDF cache */
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/* BSDF cache retention policies */
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#define SDretainNone 0 /* free unreferenced BSDF data */
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#define SDretainBSDFs 1 /* keep loaded BSDFs in memory */
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#define SDretainAll 2 /* also keep cumulative cache data */
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extern int SDretainSet; /* =SDretainNone by default */
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/*****************************************************************
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* The following routines are less commonly used by applications.
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*/
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#define SDisLoaded(sd) ((sd)->rLambFront.spec.flags != 0)
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/* Report an error to the indicated stream */
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extern SDError SDreportError(SDError ec, FILE *fp);
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/* Shorten file path to useable BSDF name, removing suffix */
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extern void SDclipName(char res[SDnameLn], const char *fname);
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/* Allocate new spectral distribution function */
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extern SDSpectralDF *SDnewSpectralDF(int nc);
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/* Add component(s) to spectral distribution function */
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extern SDSpectralDF *SDaddComponent(SDSpectralDF *odf, int nadd);
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/* Free a spectral distribution function */
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extern void SDfreeSpectralDF(SDSpectralDF *df);
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/* Initialize an unused BSDF struct and assign name (calls SDclipName) */
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extern void SDclearBSDF(SDData *sd, const char *fname);
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/* Load a BSDF struct from the given file (keeps name unchanged) */
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extern SDError SDloadFile(SDData *sd, const char *fname);
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/* Free data associated with BSDF struct */
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extern void SDfreeBSDF(SDData *sd);
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/* Find writeable BSDF by name, or allocate new cache entry if absent */
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extern SDData *SDgetCache(const char *bname);
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/* Free cached cumulative distributions for BSDF component */
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extern void SDfreeCumulativeCache(SDSpectralDF *df);
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/* Sample an individual BSDF component */
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extern SDError SDsampComponent(SDValue *sv, FVECT ioVec,
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double randX, SDComponent *sdc);
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/* Convert 1-dimensional random variable to N-dimensional */
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extern void SDmultiSamp(double t[], int n, double randX);
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/* Map a [0,1]^2 square to a unit radius disk */
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extern void SDsquare2disk(double ds[2], double seedx, double seedy);
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/* Map point on unit disk to a unit square in [0,1]^2 range */
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extern void SDdisk2square(double sq[2], double diskx, double disky);
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/*****************************************************************
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* The calls below are the ones most applications require.
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* All directions are assumed to be unit vectors.
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*/
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/* Get BSDF from cache (or load and cache it on first call) */
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/* Report any problems to stderr, return NULL on failure */
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extern const SDData *SDcacheFile(const char *fname);
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/* Free a BSDF from our cache (clear all if sd==NULL) */
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extern void SDfreeCache(const SDData *sd);
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/* Query projected solid angle resolution for non-diffuse BSDF direction(s) */
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extern SDError SDsizeBSDF(double *projSA, const FVECT v1,
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const RREAL *v2, int qflags,
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const SDData *sd);
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/* Return BSDF for the given incident and scattered ray vectors */
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extern SDError SDevalBSDF(SDValue *sv, const FVECT outVec,
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const FVECT inVec, const SDData *sd);
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/* Compute directional hemispherical scattering at given incident angle */
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extern double SDdirectHemi(const FVECT inVec,
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int sflags, const SDData *sd);
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/* Sample BSDF direction based on the given random variable */
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extern SDError SDsampBSDF(SDValue *sv, FVECT ioVec, double randX,
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int sflags, const SDData *sd);
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/*****************************************************************
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* Vector math for getting between world and local BSDF coordinates.
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* Directions may be passed unnormalized to these routines.
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*/
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/* Compute World->BSDF transform from surface normal and BSDF up vector */
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extern SDError SDcompXform(RREAL vMtx[3][3], const FVECT sNrm,
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const FVECT uVec);
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/* Compute inverse transform */
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extern SDError SDinvXform(RREAL iMtx[3][3], RREAL vMtx[3][3]);
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/* Transform and normalize direction (column) vector */
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extern SDError SDmapDir(FVECT resVec, RREAL vMtx[3][3],
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const FVECT inpVec);
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/* Application-specific BSDF loading routine (not part of our library) */
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extern SDData *loadBSDF(char *name);
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/* Application-specific BSDF error translator (not part of our library) */
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extern char *transSDError(SDError ec);
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#ifdef __cplusplus
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}
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#endif
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#endif /* ! _BSDF_H_ */
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