html5+webgl仿ps羽化笔刷液态动画特效

js代码

<script id="vertexShader" type="x-shader/x-vertex">
  attribute vec4 a_position;
  
  uniform mat4 u_modelViewMatrix;
  uniform mat4 u_projectionMatrix;
  
  void main() {
    gl_Position = a_position;
  }
</script>

<script id="fragmentShader" type="x-shader/x-fragment">
  precision highp float;
  
  uniform vec2 u_resolution;
  uniform vec2 u_mouse;
  uniform float u_time;
  uniform sampler2D u_noise;
  uniform sampler2D u_buffer;
  uniform bool u_bufferpass;
  
  
  #define PI 3.141592653589793
  #define TAU 6.283185307179586
  
  vec2 getScreenSpace() {
    vec2 uv = (gl_FragCoord.xy) / min(u_resolution.y, u_resolution.x);
    
    return uv;
  }

  #define pow2(x) (x * x)

  const int samples = 2;
  const float sigma = float(samples) * 0.25;

  float gaussian(vec2 i) {
      return 1.0 / (2.0 * PI * pow2(sigma)) * exp(-((pow2(i.x) + pow2(i.y)) / (2.0 * pow2(sigma))));
  }

  vec3 blur(sampler2D sp, vec2 uv, vec2 scale) {
      vec3 col = vec3(0.0);
      float accum = 0.0;
      float weight;
      vec2 offset;

      for (int x = -samples / 2; x < samples / 2; ++x) {
          for (int y = -samples / 2; y < samples / 2; ++y) {
              offset = vec2(x, y);
              weight = gaussian(offset);
              col += texture2D(sp, uv + scale * offset).rgb * weight;
              accum += weight;
          }
      }

      return col / accum;
  }
  
  const float blurStrength = 2.;
  const float blurMultiplier = 0.998;
  
  void main() {
    vec2 uv = getScreenSpace();
    vec2 sample = gl_FragCoord.xy / u_resolution;
    
    vec3 colour = vec3(sin(uv.x)*.5+.5, sin(uv.y)*.5+.5, 1.);
    float s = texture2D(u_buffer, sample).r;
    
    vec2 ps = vec2(1.0) / u_resolution.xy;
    
    if(u_bufferpass) {
      s = (blur(u_buffer, sample + vec2(.001), ps*blurStrength) * blurMultiplier).r;
      
      float c = s * .999 + smoothstep(length(ps)*20., .0, length(uv - u_mouse)*.5) * .5;
      colour = vec3(c);
    } else {
      colour = mix(vec3(0.2), colour, sin(s)*.5+.5);
      colour *= colour*2.;
    }

    gl_FragColor = vec4(colour,1.0);
  }
  
</script>

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