50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
/*
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* Copyright 2011-2013 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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float fresnel_dielectric_cos(float cosi, float eta)
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{
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/* compute fresnel reflectance without explicitly computing
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* the refracted direction */
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float c = fabs(cosi);
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float g = eta * eta - 1 + c * c;
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float result;
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if (g > 0) {
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g = sqrt(g);
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float A = (g - c) / (g + c);
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float B = (c * (g + c) - 1) / (c * (g - c) + 1);
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result = 0.5 * A * A * (1 + B * B);
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}
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else
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result = 1.0; /* TIR (no refracted component) */
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return result;
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}
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color fresnel_conductor(float cosi, color eta, color k)
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{
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color cosi2 = color(cosi * cosi);
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color one = color(1, 1, 1);
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color tmp_f = eta * eta + k * k;
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color tmp = tmp_f * cosi2;
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color Rparl2 = (tmp - (2.0 * eta * cosi) + one) /
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(tmp + (2.0 * eta * cosi) + one);
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color Rperp2 = (tmp_f - (2.0 * eta * cosi) + cosi2) /
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(tmp_f + (2.0 * eta * cosi) + cosi2);
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return (Rparl2 + Rperp2) * 0.5;
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}
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