forked from bartvdbraak/blender
37 lines
1.2 KiB
C
37 lines
1.2 KiB
C
/*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version 2
|
|
* of the License, or (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software Foundation,
|
|
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
|
|
*/
|
|
|
|
float fresnel_dielectric(vector Incoming, normal Normal, float eta)
|
|
{
|
|
/* compute fresnel reflectance without explicitly computing
|
|
* the refracted direction */
|
|
float c = fabs(dot(Incoming, Normal));
|
|
float g = eta * eta - 1 + c * c;
|
|
float result;
|
|
|
|
if (g > 0) {
|
|
g = sqrt(g);
|
|
float A = (g - c) / (g + c);
|
|
float B = (c * (g + c) - 1) / (c * (g - c) + 1);
|
|
result = 0.5 * A * A * (1 + B * B);
|
|
}
|
|
else
|
|
result = 1.0; /* TIR (no refracted component) */
|
|
|
|
return result;
|
|
}
|
|
|