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//
// Fragment shader for environment mapping with an
// equirectangular 2D texture
//
// Authors: John Kessenich, Randi Rost
//
// Copyright (c) 2002-2004 3Dlabs Inc. Ltd.
//
// See 3Dlabs-License.txt for license information
//
const vec3 Xunitvec = vec3 (1.0, 0.0, 0.0);
const vec3 Yunitvec = vec3 (0.0, 1.0, 0.0);
uniform vec3 BaseColor;
uniform float MixRatio;
uniform sampler2D EnvMap;
varying vec3 Normal;
varying vec3 EyeDir;
varying float LightIntensity;
void main (void)
{
// Compute reflection vector
vec3 reflectDir = reflect(EyeDir, Normal);
// Compute altitude and azimuth angles
vec2 index;
index.y = dot(normalize(reflectDir), Yunitvec);
reflectDir.y = 0.0;
index.x = dot(normalize(reflectDir), Xunitvec) * 0.5;
// Translate index values into proper range
if (reflectDir.z >= 0.0)
index = (index + 1.0) * 0.5;
else
{
index.t = (index.t + 1.0) * 0.5;
index.s = (-index.s) * 0.5 + 1.0;
}
// if reflectDir.z >= 0.0, s will go from 0.25 to 0.75
// if reflectDir.z < 0.0, s will go from 0.75 to 1.25, and
// that's OK, because we've set the texture to wrap.
// Do a lookup into the environment map.
vec3 envColor = vec3 (texture2D(EnvMap, index));
// Add lighting to base color and mix
vec3 base = LightIntensity * BaseColor;
envColor = mix(envColor, base, MixRatio);
gl_FragColor = vec4 (envColor, 1.0);
}
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