// undulatingBurnOut — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/undulatingBurnOut.glsl
// Author: pthrasher
// License: MIT
// Description: A circle with a wavy edge burns out from the center to reveal the incoming image

uniform shader _from;
uniform shader _to;
uniform float2 _resolution;
uniform float progress;
uniform float ratio;

vec4 getFromColor(vec2 uv) { return vec4(unpremul(_from.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }
vec4 getToColor(vec2 uv) { return vec4(unpremul(_to.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }

uniform float smoothness; 

uniform vec2 center; 

uniform vec3 color; 

const float M_PI = 3.14159265358979323846;

float quadraticInOut(float t) {
  float p = 2.0 * t * t;
  return t < 0.5 ? p : -p + (4.0 * t) - 1.0;
}

float getGradient(float r, float dist) {
  float d = r - dist;
  return mix(
    smoothstep(-smoothness, 0.0, r - dist * (1.0 + smoothness)),
    -1.0 - step(0.005, d),
    step(-0.005, d) * step(d, 0.01)
  );
}

float getWave(vec2 p){
  vec2 _p = p - center; 
  float rads = atan(_p.y, _p.x);
  float degs = degrees(rads) + 180.0;
  vec2 range = vec2(0.0, M_PI * 30.0);
  vec2 domain = vec2(0.0, 360.0);
  float ratio = (M_PI * 30.0) / 360.0;
  degs = degs * ratio;
  float x = progress;
  float magnitude = mix(0.02, 0.09, smoothstep(0.0, 1.0, x));
  float offset = mix(40.0, 30.0, smoothstep(0.0, 1.0, x));
  float ease_degs = quadraticInOut(sin(degs));
  float deg_wave_pos = (ease_degs * magnitude) * sin(x * offset);
  
  
  
  return x - max(smoothness, 0.01) * (1.0 - smoothstep(0.0, 0.1, x)) + deg_wave_pos;
}

vec4 transition(vec2 p) {
  float dist = distance(center, p);
  float m = getGradient(getWave(p), dist);
  vec4 cfrom = getFromColor(p);
  vec4 cto = getToColor(p);
  return mix(mix(cfrom, cto, m), mix(cfrom, vec4(color, 1.0), 0.75), step(m, -2.0));
}

half4 main(float2 _coord) {
  vec2 _uv = _coord / _resolution;
  vec4 _c = clamp(transition(vec2(_uv.x, 1.0 - _uv.y)), 0.0, 1.0);
  return half4(_c.rgb * _c.a, _c.a);
}