distance-field.glsl

#if VERTEX
$input a_position, a_texcoord0
$output v_texcoord0

#include "common.glsl"

void main() {
	v_texcoord0 = a_texcoord0;
	gl_Position = mul(u_modelViewProj, vec4(a_position, 1.0));
}
#endif

#if FRAGMENT
$input v_texcoord0

#include "common.glsl"

SAMPLER2D(s_tex_color, 0);

const float distancethreshold = 0.5;

float aastep(float threshold, float dist) {
	float afwidth = 0.75 * length(vec2(dFdx(dist), dFdy(dist)));
	return smoothstep(threshold - afwidth, threshold + afwidth, dist);
}

float sample(vec2 tc, vec2 offset, float width) {
	float dist = texture2D(s_tex_color, tc - offset).a;
	return aastep(distancethreshold - width, dist);
}

void main() {
	vec4 out_color = vec4(vec3_splat(1.0), 0.0);
	vec2 tc = v_texcoord0;
	out_color += vec4(0.0, 0.0, 0.0, 1.0) * sample(tc, vec2(0.0, 0.0025), 0.125);
	out_color += vec4(4.0, 4.0, 4.0, 1.0) * sample(tc, vec2(0.0, 0.0), 0.0);
	out_color.a = clamp(out_color.a, 0.0, 1.0);

	gl_FragColor = out_color;
}
#endif