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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);
//---- this is the original code (buggy):
// // Compute altitude and azimuth angles
//
// 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.
//---- end of the original code
// this is the version implemented from the OpenGL-1.2 programming guide:
reflectDir.z += 1.0;
float inv_m = 0.5/sqrt(dot(reflectDir,reflectDir));
vec2 index = reflectDir.xy * inv_m + 0.5;
// Do a lookup into the environment map.
vec4 envColor = vec4 (texture2D(EnvMap, index));
// Add lighting to base color and mix
//vec3 base = LightIntensity * BaseColor;
envColor = mix(envColor, gl_Color, MixRatio);
gl_FragColor =envColor;
}
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