// parametric_glitch — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/parametric_glitch.glsl
// Author: Yoni Maltsman @friendlyspinach
// License: MIT
// Description: A crossfade with glitchy horizontal bands and color shifts

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 ampx; 

uniform float ampy; 

vec4 transition (vec2 uv) {
  vec4 from = getFromColor(uv);
  vec4 to = getToColor(uv);
  float r = from.r;
  float g = from.g;
  float b = from.b;
  float sphere = r*r + g*g + b*b - 1.0; 
  float spiralX = cos(sphere - uv.x/(progress + .01));
  float spiralY = sin(sphere - uv.y/(progress+.01));
  vec2 st = uv;
  st.x = fract(ampx*st.x*spiralX); 
  st.y = fract(ampy*st.y*spiralY);
  vec2 diff = uv - st;
  from = getFromColor(uv + progress*diff);
  return mix(from, to, progress);
}

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);
}