star-sf

Set of surface and volume scattering functions
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ssf_fresnel_constant.c (2166B)

      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_fresnel_c.h"
     18 
     19 struct fresnel_constant {
     20   double k; /* in [0, 1] */
     21 };
     22 
     23 /*******************************************************************************
     24  * Private functions
     25  ******************************************************************************/
     26 static res_T
     27 fresnel_constant_init(struct mem_allocator* allocator, void* fresnel)
     28 {
     29   struct fresnel_constant* f = fresnel;
     30   (void)allocator;
     31   ASSERT(fresnel);
     32   f->k = 1; /* <=> No op */
     33   return RES_OK;
     34 }
     35 
     36 static void
     37 fresnel_constant_release(void* fresnel)
     38 {
     39   (void)fresnel;
     40 }
     41 
     42 static double
     43 fresnel_constant_eval(void* fresnel, const double cos_theta_i)
     44 {
     45   struct fresnel_constant* f = fresnel;
     46   (void)cos_theta_i;
     47   return f->k;
     48 }
     49 
     50 /*******************************************************************************
     51  * Exported symbols
     52  ******************************************************************************/
     53 const struct ssf_fresnel_type ssf_fresnel_constant = {
     54   fresnel_constant_init,
     55   fresnel_constant_release,
     56   fresnel_constant_eval,
     57   sizeof(struct fresnel_constant),
     58   ALIGNOF(struct fresnel_constant)
     59 };
     60 
     61 res_T
     62 ssf_fresnel_constant_setup(struct ssf_fresnel* fresnel, const double value)
     63 {
     64   struct fresnel_constant* f;
     65   if(!fresnel || !FRESNEL_TYPE_EQ(&fresnel->type, &ssf_fresnel_constant))
     66     return RES_BAD_ARG;
     67   if(value < 0 || value > 1)
     68     return RES_BAD_ARG;
     69   f = fresnel->data;
     70   f->k = value;
     71   return RES_OK;
     72 }
     73