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32 
33 #ifndef COIN_INTERNAL
34 #error this is a private header file
35 #endif /* !COIN_INTERNAL */
36 
37 #ifndef SO_VSMLOOKUP_GLSL_H
38 #define SO_VSMLOOKUP_GLSL_H
39 
40 static const char VSMLOOKUP_shadersource[] =
41   "float VsmLookup(in vec4 map, in float dist, in float epsilon, float bleedthreshold)\n"
42   "{\n"
43   "  float mapdist = map.x;\n"
44   "\n"
45   "  // replace 0.0 with some factor > 0.0 to make the light affect even parts in shadow\n"
46   "  float lit_factor = dist <= mapdist ? 1.0 : 0.0;\n"
47   "  float E_x2 = map.y;\n"
48   "  float Ex_2 = mapdist * mapdist;\n"
49   "  float variance = min(max(E_x2 - Ex_2, 0.0) + epsilon, 1.0);\n"
50   "\n"
51   "  float m_d = mapdist - dist;\n"
52   "  float p_max = variance / (variance + m_d * m_d);\n"
53   "\n"
54   "  p_max *= smoothstep(bleedthreshold, 1.0, p_max);\n"
55   "\n"
56   "  return max(lit_factor, p_max);\n"
57   "}\n";
58 
59 #endif /* ! SO_VSMLOOKUP_GLSL_H */
60