#version 330

uniform sampler2D tex0;
uniform sampler2D tex1;
uniform float progress;

in vec2 vsoTexCoord;
out vec4 fragColor;

void main() {
  vec2 center = vec2(.5);
  vec2 offset = vsoTexCoord - center;

  float angle = progress * radians(180) * 2;
  float sinTheta = sin(angle);
  float cosTheta = cos(angle);
  vec2 rotatedOffset = vec2(cosTheta * offset.x - sinTheta * offset.y, sinTheta * offset.x + cosTheta * offset.y);

  vec2 distortedTexCoord = center + rotatedOffset;

  vec4 color1 = texture(tex0, vsoTexCoord);
  vec4 color2 = texture(tex1, distortedTexCoord);

  fragColor = mix(color1, color2, smoothstep(0., 1., progress));
}