forked from bartvdbraak/blender
50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
/*
|
|
* Copyright 2011-2013 Blender Foundation
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
float fresnel_dielectric_cos(float cosi, float eta)
|
|
{
|
|
/* compute fresnel reflectance without explicitly computing
|
|
* the refracted direction */
|
|
float c = fabs(cosi);
|
|
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;
|
|
}
|
|
|
|
color fresnel_conductor(float cosi, color eta, color k)
|
|
{
|
|
color cosi2 = color(cosi * cosi);
|
|
color one = color(1, 1, 1);
|
|
color tmp_f = eta * eta + k * k;
|
|
color tmp = tmp_f * cosi2;
|
|
color Rparl2 = (tmp - (2.0 * eta * cosi) + one) /
|
|
(tmp + (2.0 * eta * cosi) + one);
|
|
color Rperp2 = (tmp_f - (2.0 * eta * cosi) + cosi2) /
|
|
(tmp_f + (2.0 * eta * cosi) + cosi2);
|
|
return (Rparl2 + Rperp2) * 0.5;
|
|
}
|
|
|