precision highp float;
varying vec2 uv0;

uniform sampler2D inputImageTexture;
uniform sampler2D inputImageTexture2;
uniform int imageWidth;
uniform int imageHeight;
uniform float progress;
uniform float speed; // = 2.0;

vec4 getFromColor(vec2 p)
{
    return texture2D(inputImageTexture,p);
}

vec4 getToColor(vec2 p)
{
    return texture2D(inputImageTexture2,p);
}

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));
}

void main(void)
{
    vec4 resultColor = transition(uv0);
    gl_FragColor=resultColor;
}