star-sf

Set of surface and volume scattering functions
git clone git://git.meso-star.fr/star-sf.git
Log | Files | Refs | README | LICENSE

ssf_specular_dielectric_dielectric_interface.c (4470B)

      1 /* Copyright (C) 2016-2018, 2021-2025 |Méso|Star> (contact@meso-star.com)
      2  *
      3  * This program is free software: you can redistribute it and/or modify
      4  * it under the terms of the GNU General Public License as published by
      5  * the Free Software Foundation, either version 3 of the License, or
      6  * (at your option) any later version.
      7  *
      8  * This program is distributed in the hope that it will be useful,
      9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
     11  * GNU General Public License for more details.
     12  *
     13  * You should have received a copy of the GNU General Public License
     14  * along with this program. If not, see <http://www.gnu.org/licenses/>. */
     15 
     16 #include "ssf.h"
     17 #include "ssf_bsdf_c.h"
     18 #include "ssf_optics.h"
     19 
     20 #include <rsys/double3.h>
     21 #include <star/ssp.h>
     22 
     23 struct specular_dielectric_dielectric_interface {
     24   struct ssf_fresnel* fresnel;
     25   double eta_i; /* Refractive index of the incoming medium */
     26   double eta_t; /* Refractive index of the transmissive medium */
     27 };
     28 
     29 /*******************************************************************************
     30  * Private functions
     31  ******************************************************************************/
     32 static res_T
     33 ssf_specular_dielectric_dielectric_interface_init
     34   (struct mem_allocator* allocator, void* data)
     35 {
     36   struct specular_dielectric_dielectric_interface* bsdf = data;
     37   ASSERT(bsdf);
     38   return ssf_fresnel_create
     39     (allocator, &ssf_fresnel_dielectric_dielectric, &bsdf->fresnel);
     40 }
     41 
     42 static void
     43 ssf_specular_dielectric_dielectric_interface_release(void* data)
     44 {
     45   struct specular_dielectric_dielectric_interface* bsdf = data;
     46   SSF(fresnel_ref_put(bsdf->fresnel));
     47 }
     48 
     49 static double
     50 ssf_specular_dielectric_dielectric_interface_sample
     51   (void* data,
     52    struct ssp_rng* rng,
     53    const double wo[3],
     54    const double N[3],
     55    double wi[3],
     56    int* type,
     57    double* pdf)
     58 {
     59   struct specular_dielectric_dielectric_interface* bsdf = data;
     60   struct ssf_fresnel* fresnel;
     61   double wt[3];
     62   double *refracted;
     63   double cos_wo_N;
     64   double eta; /* Ratio of eta_i / eta_t */
     65   double R;
     66   ASSERT(bsdf && rng && wi && N && wo);
     67   ASSERT(d3_is_normalized(wo) && d3_is_normalized(N));
     68   ASSERT(d3_dot(wo, N) > -1.e-6);
     69   (void)rng;
     70 
     71   eta = bsdf->eta_i / bsdf->eta_t;
     72   refracted = refract(wt, wo, N, eta);
     73   if(!refracted) { /* Total reflection */
     74     reflect(wi, wo, N);
     75     if(pdf) *pdf = INF;
     76     if(type) *type = SSF_SPECULAR | SSF_REFLECTION;
     77     return 1;
     78   }
     79   fresnel = bsdf->fresnel;
     80 
     81   cos_wo_N = MMAX(0.0, d3_dot(wo, N));
     82   SSF(fresnel_dielectric_dielectric_setup(fresnel, bsdf->eta_i, bsdf->eta_t));
     83   R = ssf_fresnel_eval(fresnel, cos_wo_N);
     84 
     85   if(pdf) *pdf = INF;
     86 
     87   /* Sample the output direction wrt R */
     88   if(ssp_rng_canonical(rng) < R) {
     89     reflect(wi, wo, N);
     90     if(type) *type = SSF_SPECULAR | SSF_REFLECTION;
     91   } else {
     92     d3_set(wi, refracted);
     93     if(type) *type = SSF_SPECULAR | SSF_TRANSMISSION;
     94   }
     95   return 1;
     96 }
     97 
     98 static double
     99 ssf_specular_dielectric_dielectric_interface_eval
    100   (void* bsdf, const double wo[3], const double N[3], const double wi[3])
    101 {
    102    (void)bsdf, (void)wo, (void)N, (void)wi;
    103    return 0.0;
    104 }
    105 
    106 static double
    107 ssf_specular_dielectric_dielectric_interface_pdf
    108   (void* bsdf, const double wo[3], const double N[3], const double wi[3])
    109 {
    110   (void)bsdf, (void)wo, (void)N, (void)wi;
    111   return 0.0;
    112 }
    113 
    114 /*******************************************************************************
    115  * Exported symbols
    116  ******************************************************************************/
    117 const struct ssf_bsdf_type ssf_specular_dielectric_dielectric_interface = {
    118   ssf_specular_dielectric_dielectric_interface_init,
    119   ssf_specular_dielectric_dielectric_interface_release,
    120   ssf_specular_dielectric_dielectric_interface_sample,
    121   ssf_specular_dielectric_dielectric_interface_eval,
    122   ssf_specular_dielectric_dielectric_interface_pdf,
    123   sizeof(struct specular_dielectric_dielectric_interface),
    124   ALIGNOF(struct specular_dielectric_dielectric_interface)
    125 };
    126 
    127 res_T
    128 ssf_specular_dielectric_dielectric_interface_setup
    129   (struct ssf_bsdf* bsdf,
    130    const double eta_i,
    131    const double eta_t)
    132 {
    133   struct specular_dielectric_dielectric_interface* data;
    134 
    135   if(!bsdf || eta_i <= 0 || eta_t <= 0)
    136     return RES_BAD_ARG;
    137   if(!BSDF_TYPE_EQ(&bsdf->type, &ssf_specular_dielectric_dielectric_interface))
    138     return RES_BAD_ARG;
    139 
    140   data = bsdf->data;
    141 
    142   data->eta_i = eta_i;
    143   data->eta_t = eta_t;
    144   return RES_OK;
    145 }
    146