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#ifdef GL_ES
precision mediump float;
#endif
uniform sampler2D HeightMap;
varying vec2 TextureCoord;
varying vec3 NormalEye;
varying vec3 TangentEye;
varying vec3 BitangentEye;
void main(void)
{
const vec4 LightSourceAmbient = vec4(0.1, 0.1, 0.1, 1.0);
const vec4 LightSourceDiffuse = vec4(0.8, 0.8, 0.8, 1.0);
const vec4 LightSourceSpecular = vec4(0.8, 0.8, 0.8, 1.0);
const vec4 MaterialAmbient = vec4(1.0, 1.0, 1.0, 1.0);
const vec4 MaterialDiffuse = vec4(1.0, 1.0, 1.0, 1.0);
const vec4 MaterialSpecular = vec4(0.2, 0.2, 0.2, 1.0);
const float MaterialShininess = 100.0;
const float height_factor = 13.0;
// Get the data from the height map
float height0 = texture2D(HeightMap, TextureCoord).x;
float heightX = texture2D(HeightMap, TextureCoord + vec2(TextureStepX, 0.0)).x;
float heightY = texture2D(HeightMap, TextureCoord + vec2(0.0, TextureStepY)).x;
vec2 dh = vec2(heightX - height0, heightY - height0);
// Adjust the normal based on the height map data
vec3 N = NormalEye - height_factor * dh.x * TangentEye -
height_factor * dh.y * BitangentEye;
N = normalize(N);
// In the lighting model we are using here (Blinn-Phong with light at
// infinity, viewer at infinity), the light position/direction and the
// half vector is constant for the all the fragments.
vec3 L = normalize(LightSourcePosition.xyz);
vec3 H = normalize(LightSourceHalfVector);
// Calculate the diffuse color according to Lambertian reflectance
vec4 diffuse = MaterialDiffuse * LightSourceDiffuse * max(dot(N, L), 0.0);
// Calculate the ambient color
vec4 ambient = MaterialAmbient * LightSourceAmbient;
// Calculate the specular color according to the Blinn-Phong model
vec4 specular = MaterialSpecular * LightSourceSpecular *
pow(max(dot(N,H), 0.0), MaterialShininess);
// Calculate the final color
gl_FragColor = ambient + specular + diffuse;
//gl_FragColor = vec4(height_diff_raw.xy, 0.0, 1.0);
//gl_FragColor = vec4(height_diff_scaled.xy, 0.0, 1.0);
//gl_FragColor = vec4(Tangent, 1.0);
}
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