1 /// ============================================================================
3 Copyright (C) 2004 Robert Beckebans <trebor_7@users.sourceforge.net>
4 Please see the file "AUTHORS" for a list of contributors
6 This program is free software; you can redistribute it and/or
7 modify it under the terms of the GNU General Public License
8 as published by the Free Software Foundation; either version 2
9 of the License, or (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
15 See the GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
21 /// ============================================================================
23 // fresnel approximation
24 float fast_fresnel(float3 I, float3 N, float3 fresnel_values)
26 float power = fresnel_values.x;
27 float scale = fresnel_values.y;
28 float bias = fresnel_values.z;
30 return bias + pow(1.0 - dot(I, N), power) * scale;
33 float3 CG_Expand(float3 v)
35 return (v - 0.5) * 2; // expand a range-compressed vector