Springs.js

/** @license 
  * Copyright 2023 Google LLC.
  * SPDX-License-Identifier: Apache-2.0 
  */

class Springs {
    static Tags = ['2d'];

    constructor(glsl, gui) {
        this.glsl = glsl;
        this.reset();
        this.params = {waveRate:4.0};
        gui.add(this, 'reset');
        gui.add(this.params, 'waveRate', 0.0, 8.0);
    }

    reset() {
        const {glsl} = this;
        for (let i=0; i<2; ++i)
        this.points = glsl({FP:`
            XY*rot2(PI+0.1)*0.6+vec2(0,0.3),0,(UV.x+UV.y)*10.0
        `}, {size:[64, 64], format:'rgba32f', story:2, tag:'points'});
    }

    frame(glsl, {time}) {
        const {points} = this;

        const next = glsl({time, ...this.params, points:points[0], prev:points[1], FP:`
            FOut = points(I);
            if ((I.x%8 == 0 && I.y==0) || I == ivec2(ViewSize.x-1,0)) return;
            vec3 vel = FOut.xyz-prev(I).xyz;
            vel.y -= 0.0005;
            FOut += vec4(vel, waveRate/60.0);
            if (FOut.y<-0.8) {
                FOut.x -= vel.x*0.8;
            }
        `}, {size:points[0].size, format:'rgba32f', story:2, tag:'next'});

        for (let i=0; i<8; ++i)
        glsl({time, FP:`
            vec4 relax(vec3 p, vec3 p0, float dist) {
                vec3 dp = p-p0;
                return vec4(p0+dp/(length(dp)+1e-10)*dist, 1.0);
            }
            void fragment() {
                vec4 p = FOut = Src(I);
                if ((I.x%8 == 0 && I.y==0) || I == ivec2(ViewSize.x-1,0)) return;
                vec4 acc = vec4(0);
                ivec2 i, D = ViewSize;
                float f0 = sin(p.w);
                const int R = 1;
                for (i.y=-R; i.y<=R; ++i.y) if (I.y+i.y>=0 && I.y+i.y<D.y)
                for (i.x=-R; i.x<=R; ++i.x) if (I.x+i.x>=0 && I.x+i.x<D.x) {
                    if (abs(i.x)+abs(i.y)>1) continue;
                    if (i==ivec2(0)) continue;
                    vec4 p1 = Src(I+i);
                    float f1 = sin(p1.w);
                    float f = 1.0;// + 0.5*0.5*(f0+f1);
                    acc += relax(p.xyz, p1.xyz, f*length(vec2(i)/vec2(D)));
                }
                FOut.xyz = acc.xyz/acc.w;
                if (FOut.y<-0.8) {
                    FOut.y = -0.8;
                    FOut.x = mix(FOut.x, p.x, 0.9);
                }
            }`}, next);
        glsl({next:next[0], FP:`next(I)`}, points)

        glsl({FP:`float(XY.y<-0.8)*0.5`})

        const [w, h] = points[0].size;
        glsl({points:next[0], Mesh:[w-1,h-1], Aspect:'y', 
        Blend: 'd*(1-sa)+s*sa',VP:`
        points(VID.xy).xy,0,1`,
        FP:`sqrt(isoline(UV.x*float(Mesh.x))+isoline(UV.y*float(Mesh.y)))`});
    }
}