/** Demo of using an Anti-aliasing blur pass based on edge detection
in a deferred shading system. Fragment shader */

#version 110

uniform sampler2D normalMap;
uniform sampler2D colourMap;

uniform float weight;
uniform vec2 texSize;

void main()
{
    const int NUM_SAMPLES = 8;
    const float texel = 1.0;

    vec2 filter[NUM_SAMPLES];
    filter[0] = vec2(-texel,  texel);
    filter[1] = vec2( texel, -texel);
    filter[2] = vec2(-texel,  texel);
    filter[3] = vec2(-texel, -texel);

    filter[4] = vec2(-texel, 0.0);
    filter[5] = vec2( texel, 0.0);
    filter[6] = vec2(0.0,   -texel);
    filter[7] = vec2(0.0,   -texel);

    vec4 tex = texture2D(normalMap, gl_TexCoord[0].st);
    float factor = 0.0;

    for(int i = 0; i < 4; i++)
    {
        vec4 t = texture2D(normalMap, 
                           gl_TexCoord[0].st + (filter[i] / texSize));
        t -= tex;

        factor += dot(t, t);
    }

    factor = min(1.0, factor) * weight;

    vec4 colour = vec4(0.0, 0.0, 0.0, 1.0);

    for(int i = 0; i < 8; i++)
        colour += texture2D(colourMap, 
                            gl_TexCoord[0].st + (filter[i] / texSize) * factor);

    colour += 2.0 * texture2D(colourMap, gl_TexCoord[0].st);

    gl_FragColor = colour * 0.1;
}