第 10 课：Noise Texture

实现

uniform vec2 iResolution;
uniform float iTime;
uniform sampler2D iChannel0;

float sdfBox(vec2 center, vec2 size, vec2 pos) {
  vec2 d = abs(pos - center) - size;
  return length(max(d, 0.0)) + min(max(d.x, d.y), 0.0);
}

void main() {
  vec2 aspect = vec2(iResolution.x / iResolution.y, 1.0);
  vec2 uv = gl_FragCoord.xy / iResolution.xy;

  float time = iTime * 0.25;

  vec4 noise = texture(iChannel0, fract(uv - vec2(0.0,time)));

  float distortion = noise.x; // sample noise value
  distortion *= uv.y;
  distortion *= 0.4;

  vec2 center = vec2(0.5, 0.4);
  float shape = sdfBox(center * aspect, vec2(0.5, 0.15), uv * aspect);
  shape = max(shape - distortion, 0.0);

  float t = 1.0 - smoothstep(0.0, 0.1, shape);
  vec3 color = vec3(1.5, 1.0, 0.25) * t * (distortion + 0.6);

  gl_FragColor = vec4(color * color, 1.0);
}