// pinwheel — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/pinwheel.glsl
// Author: Mr Speaker
// License: MIT
// Description: A spinning pinwheel reveals 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 speed; 

vec4 transition(vec2 uv) {
  
  vec2 p = uv.xy / vec2(1.0).xy;
  
  float circPos = atan(p.y - 0.5, p.x - 0.5) + progress * speed;
  float modPos = mod(circPos, 3.1415 / 4.);
  float signed = sign(progress - modPos);
  
  return mix(getToColor(p), getFromColor(p), step(signed, 0.5));
  
}

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);
}