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/*
* 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;
}
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