blob: de2d40a849c5f04d7e50632fb6c6a2fb73a3cb4d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
/*
* 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;
}
|
