/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// Display a signed distance field as color
//
// It will be orange outside the shape (positive distance), and blue
// inside (negative distance).
// 
// Color will cycle every 10px.
//
// The shape outline (distance = 0) is drawn as a thin white outline.
//
// NaNs and infinite values will be drawn as red and yellow respectively.
//
// Example usage:
//
// #include debug
//
// void main(void) {
//   float d = compute_some_distance_in_pixels(...);
//   oFragColor = debug_sdf(d);
// }
//
vec4 debug_sdf(float d) {
    if (isnan(d)) {
        return vec4(1.0, 0.0, 0.0, 1.0);
    }
    if (isinf(d)) {
        return vec4(1.0, 1.0, 0.0, 1.0);
    }

    vec3 color = (d > 0.0) ? vec3(0.9, 0.6, 0.3) : vec3(0.6, 0.8, 1.0);
    color *= 1.0 - exp(-0.32 * abs(d));
    color *= fract(d / 10.0) * 0.4 + 0.6;
#ifdef SWGL
    // SWGL doesn't support smoothstep() for now
    color = mix(color, vec3(1.0), step(abs(d), 2.0));
#else
    color = mix(color, vec3(1.0), smoothstep(2.0, 0.0, abs(d)));
#endif
    return vec4(color, 1.0);
}