uniform sampler2D tex;
uniform float smoothness;

void main()
{
	const vec2 pix_sz = vec2(1.0 / 512.0, 1.0 / 256.0);	// TODO: uniform

	vec2 uv = gl_TexCoord[0].st;
	float dist = texture2D(tex, uv).a;

	float dfdu = texture2D(tex, uv + vec2(pix_sz.x, 0.0)).a - dist;
	float dfdv = texture2D(tex, uv + vec2(0.0, pix_sz.y)).a - dist;
	vec2 grad = normalize(vec2(dfdu, dfdv));

	float glyph = smoothstep(0.47 - smoothness, 0.47 + smoothness, dist);
	float outline = smoothstep(0.54 - smoothness, 0.54 + smoothness, dist);

	float beveldot = max(dot(grad, normalize(vec2(1.0, 1.0))), 0.0);
	vec3 bevelcol = mix(vec3(0.05, 0.1, 0.6), vec3(1.0, 0.2, 0.8), beveldot);

	gl_FragColor.rgb = mix(bevelcol, vec3(1.0), outline);
	gl_FragColor.a = glyph;
}