uniform sampler2D bgl_RenderedTexture;
uniform sampler2D bgl_DepthTexture;


vec2 texcoord = vec2(gl_TexCoord[0]).st;


uniform vec2 bgl_TextureCoordinateOffset[9];

vec4 prewitt(sampler2D image, vec2 coords)
{
    vec4 samp[9];
	vec4 border;
	vec4 texcol = texture(image, texcoord);

    for (int i = 0; i < 9; i++)
    {
        samp[i] = texture(image, gl_TexCoord[0].st + bgl_TextureCoordinateOffset[i]);
    }

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

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

	border.rgb = sqrt((horizEdge.rgb * horizEdge.rgb) + (vertEdge.rgb * vertEdge.rgb));


float br = smoothstep(.005, .01, border.r);
float bg = smoothstep(.005, .01, border.g);
float bb = smoothstep(.005, .01, border.b);


   	texcol.rgb = vec3(mix(1., .0, max(max(br,bg),bb)));
	

return texcol;
}

void main(void)
{
    gl_FragColor = prewitt(bgl_DepthTexture, texcoord);
}