Outline Shader (UPBGE)

//icon=MATERIAL
uniform sampler2D bgl_RenderedTexture;
uniform vec2 bgl_TextureCoordinateOffset[9];

void main(void)
{
    vec4 samples[9];

    for (int i = 0; i < 9; i++)
    {
        samples[i] = texture2D(bgl_RenderedTexture,
                              gl_TexCoord[0].st + bgl_TextureCoordinateOffset[i]);
    }

    vec4 horizEdge = samples[2] + (2.0*samples[5]) + samples[8] -
            (samples[0] + (2.0*samples[3]) + samples[6]);

    vec4 vertEdge = samples[0] + (2.0*samples[1]) + samples[2] -
            (samples[6] + (2.0*samples[7]) + samples[8]);

    vec3 sobel = sqrt((horizEdge.rgb * horizEdge.rgb) +
                            (vertEdge.rgb * vertEdge.rgb));

    vec3 outliner = vec3(1);
    if (length(sobel) > 0.8){
        outliner = vec3(0);
    }

    gl_FragColor.xyz = texture2D(bgl_RenderedTexture, gl_TexCoord[0].st).xyz;

    gl_FragColor.xyz *= outliner;

    gl_FragColor.a = 1.0;
}