#version 330

in vec2 fragTexCoord;
in vec4 fragColor;

uniform sampler2D texture0;
uniform vec4 colDiffuse;
uniform vec2 resolution;
uniform vec2 direction;   // (1,0) for horizontal pass, (0,1) for vertical pass

out vec4 finalColor;

void main()
{
    vec2 texel = direction / resolution;

    // 9-tap Gaussian, weights from Pascal's-triangle-style approximation
    const float weight[5] = float[](
        0.227027, 0.1945946, 0.1216216, 0.054054, 0.016216
    );

    vec4 color = texture(texture0, fragTexCoord) * weight[0];

    for (int i = 1; i < 4; i++) {
        vec2 offset = texel * float(i);
        color += texture(texture0, fragTexCoord + offset) * weight[i];
        color += texture(texture0, fragTexCoord - offset) * weight[i];
    }

    finalColor = color * colDiffuse * fragColor * 1.8;
}