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HTML

              
                <script language="javascript" type="text/javascript" 
  <script src="https://threejs.org/build/three.js"></script>   

              
            
!

CSS

              
                body {margin:0px; padding:0px; overflow: hidden}
              
            
!

JS

              
                let fluid, paint, count = 0, canvas;
function init() {
    const renderer = new
        THREE.WebGLRenderer({ antialias: true });
    renderer.setSize(window.innerWidth, window.innerHeight);
    canvas = renderer.domElement;
    document.body.appendChild(canvas);

  // Calculate half fov radians for camera setup
  const fov = 65;
  const hFovRadian = fov / 2 / 180 * Math.PI;
  const cz = window.innerHeight / 2 / Math.tan(hFovRadian);

  // Setup camera
  const camera = new THREE.PerspectiveCamera(fov, window.innerWidth/window.innerHeight, 0.1, cz * 4 );
  camera.position.z = cz;

  // Create context object to hold renderer, camera and dimensions
  const context = { renderer, camera, width: window.innerWidth, height: window.innerHeight };

  // Initialize fluid and paint simulations
  fluid = new Fluid(context);
  paint = new Paint(context);
}

async function animate() {
    if (count % 640 == 0) {
        fluid.init();
        paint.init();
    }
    count ++;

    fluid.update();
    fluid.draw();
    paint.update(fluid.getVelocity());
    paint.draw();
    requestAnimationFrame(animate);
}


//----------------------------------------

class Fluid {
    constructor(context) {
        this.context = context;
        this.speed = 4;
        this.forceInitMaterial = this.createShaderMaterial(forceInitFrag);
        this.divergenceMaterial = this.createShaderMaterial(divergenceFrag);
        this.advectionMaterial = this.createShaderMaterial(advectionFrag);
        this.pressureMaterial = this.createShaderMaterial(pressureFrag);
        this.updateMaterial = this.createShaderMaterial(forceUpdateFrag);
        this.renderMaterial = this.createShaderMaterial(forceRenderFrag);
        this.velocity = [this.createRenderTarget(), this.createRenderTarget()];
        this.pressure = [this.createRenderTarget(), this.createRenderTarget()];
        this.divergence = this.createRenderTarget();
        this.advection = this.createRenderTarget();
        this.blank = this.createRenderTarget();

        // Main Scene
        this.mainScene = new THREE.Scene();
        this.mainMesh = this.createMesh(0, 0, this.context.width, this.context.height);
        this.mainScene.add(this.mainMesh);

        this.init();
    }

    init() {
        this.velocityIndex = 0;
        this.context.renderer.setRenderTarget(this.velocity[0]);
        this.mainMesh.material = this.forceInitMaterial;
        this.forceInitMaterial.uniforms.seed = { value: Math.random() * 100.0 }
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }

    createShaderMaterial(frag) {
        return new THREE.ShaderMaterial({
            vertexShader: vert,
            fragmentShader: frag,
            uniforms: { tex: { value: null }, res: { value: [this.context.width, this.context.height] }, speed: { value: this.speed } }
        });
    }

    createRenderTarget() {
        return new THREE.WebGLRenderTarget(this.context.width, this.context.height, {
            format: THREE.RGBAFormat,
            type: THREE.FloatType
        })
    }

    createMesh(cx, cy, w, h) {
        const geometry = new THREE.PlaneGeometry(w, h);
        const material = new THREE.MeshBasicMaterial({ color: 0xff0000 });
        const mesh = new THREE.Mesh(geometry, material);
        mesh.position.x = cx;
        mesh.position.y = cy;
        return mesh;
    }

    update() {
        this.updateAdvection();
        this.updateDivergence();
        this.updatepPressure();
        this.updateVelocity();
    }

    updateAdvection() {
        this.context.renderer.setRenderTarget(this.advection);
        this.mainMesh.material = this.advectionMaterial;
        this.advectionMaterial.uniforms.tex = {value: this.velocity[this.velocityIndex].texture};
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }
    
    updateDivergence() {
        this.context.renderer.setRenderTarget(this.divergence);
        this.mainMesh.material = this.divergenceMaterial;
        this.divergenceMaterial.uniforms.tex = {value: this.advection.texture};
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }

    updatepPressure() {
        this.context.renderer.setRenderTarget(this.pressure[0]);
        this.context.renderer.clear();
        this.context.renderer.setRenderTarget(null);

        for (let i = 0; i < 4; i++) {
            let i0 = i % 2;
            let i1 = (i + 1) % 2;
            const prevPressure = this.pressure[i0];
            const nextPressure = this.pressure[i1];

            this.context.renderer.setRenderTarget(nextPressure);
            this.mainMesh.material = this.pressureMaterial;
            this.pressureMaterial.uniforms.tex = {value: prevPressure.texture};
            this.pressureMaterial.uniforms.divergence = { value: this.divergence.texture };
            this.context.renderer.render(this.mainScene, this.context.camera);
            this.context.renderer.setRenderTarget(null);
        }
    }

    updateVelocity() {
        const i1 = (this.velocityIndex + 1) % 2;
        const nextVelocity = this.velocity[i1];
        this.velocityIndex = i1;

        this.context.renderer.setRenderTarget(nextVelocity);
        this.mainMesh.material = this.updateMaterial;
        this.updateMaterial.uniforms.pressure = {value: this.pressure[1].texture };
        this.updateMaterial.uniforms.advection = { value: this.advection.texture };
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }

    draw() {
        this.mainMesh.material = this.renderMaterial;
        this.renderMaterial.uniforms.tex = {value: this.getVelocity().texture}
        this.context.renderer.render(this.mainScene, this.context.camera);
    }

    getVelocity() {
        return this.velocity[this.velocityIndex];
    }
}

class Paint {
    constructor(context) {
        this.context = context;
        this.speed = 4;
        this.initMaterial = this.createShaderMaterial(paintInitFrag);
        this.updateMaterial = this.createShaderMaterial(paintUpdateFrag);
        this.renderMaterial = this.createShaderMaterial(paintRenderFrag);
        this.paint = [this.createRenderTarget(), this.createRenderTarget()];

        // Main Scene
        this.mainScene = new THREE.Scene();
        this.mainMesh = this.createMesh(0, 0, this.context.width, this.context.height);
        this.mainScene.add(this.mainMesh);

        this.init();
    }

    init() {
        this.paintIndex = 0;
        this.context.renderer.setRenderTarget(this.paint[0]);
        this.mainMesh.material = this.initMaterial;
        this.initMaterial.uniforms.seed = { value: Math.random() * 100.0 }
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }

    createShaderMaterial(frag) {
        return new THREE.ShaderMaterial({
            vertexShader: vert,
            fragmentShader: frag,
            uniforms: { tex: { value: null }, res: { value: [this.context.width, this.context.height] }, speed: { value: this.speed } }
        });
    }

    createRenderTarget() {
        return new THREE.WebGLRenderTarget(this.context.width, this.context.height, {
            format: THREE.RGBAFormat,
            type: THREE.FloatType
        })
    }

    createMesh(cx, cy, w, h) {
        const geometry = new THREE.PlaneGeometry(w, h);
        const material = new THREE.MeshBasicMaterial({ color: 0xff0000 });
        const mesh = new THREE.Mesh(geometry, material);
        mesh.position.x = cx;
        mesh.position.y = cy;
        return mesh;
    }

    update(velocity) {
        const i0 = this.paintIndex % 2;
        const i1 = (this.paintIndex + 1) % 2;
        const prevPaint = this.paint[i0];
        const nextPaint = this.paint[i1];
        this.paintIndex = i1;

        this.context.renderer.setRenderTarget(nextPaint);
        this.mainMesh.material = this.updateMaterial;
        this.updateMaterial.uniforms.tex = {value: prevPaint.texture };
        this.updateMaterial.uniforms.velocity = { value: velocity.texture };
        this.context.renderer.render(this.mainScene, this.context.camera);
        this.context.renderer.setRenderTarget(null);
    }

    draw() {
        this.mainMesh.material = this.renderMaterial;
        this.renderMaterial.uniforms.tex = {value: this.getPaint().texture}
        this.context.renderer.render(this.mainScene, this.context.camera);
    }

    getPaint() {
        return this.paint[this.paintIndex];
    }
}

// SHADERS


const noise = `
/*
Simplex Noise code is from:
(Shader Library) Simplex Noise in GLSL
http://www.geeks3d.com/20110317/shader-library-simplex-noise-glsl-opengl/
*/

#define  NORMALIZE_GRADIENTS
#undef  USE_CIRCLE
#define COLLAPSE_SORTNET

    float permute(float x0,vec3 p) {
        float x1 = mod(x0 * p.y, p.x);
        return floor(  mod( (x1 + p.z) *x0, p.x ));
    }
    vec2 permute(vec2 x0,vec3 p) {
        vec2 x1 = mod(x0 * p.y, p.x);
        return floor(  mod( (x1 + p.z) *x0, p.x ));
    }
    vec3 permute(vec3 x0,vec3 p) {
        vec3 x1 = mod(x0 * p.y, p.x);
        return floor(  mod( (x1 + p.z) *x0, p.x ));
    }
    vec4 permute(vec4 x0,vec3 p) {
        vec4 x1 = mod(x0 * p.y, p.x);
        return floor(  mod( (x1 + p.z) *x0, p.x ));
    }

    //uniform vec4 pParam;
    // Example constant with a 289 element permutation
    const vec4 pParam = vec4( 17.0*17.0, 34.0, 1.0, 7.0);

    float taylorInvSqrt(float r)
    {
        return ( 0.83666002653408 + 0.7*0.85373472095314 - 0.85373472095314 * r );
    }

    float simplexNoise2(vec2 v)
    {
        const vec2 C = vec2(0.211324865405187134, // (3.0-sqrt(3.0))/6.;
                            0.366025403784438597); // 0.5*(sqrt(3.0)-1.);
        const vec3 D = vec3( 0., 0.5, 2.0) * 3.14159265358979312;
        // First corner
        vec2 i  = floor(v + dot(v, C.yy) );
        vec2 x0 = v -   i + dot(i, C.xx);

        // Other corners
        vec2 i1  =  (x0.x > x0.y) ? vec2(1.,0.) : vec2(0.,1.) ;

        //  x0 = x0 - 0. + 0. * C
        vec2 x1 = x0 - i1 + 1. * C.xx ;
        vec2 x2 = x0 - 1. + 2. * C.xx ;

        // Permutations
        i = mod(i, pParam.x);
        vec3 p = permute( permute(
                                  i.y + vec3(0., i1.y, 1. ), pParam.xyz)
                         + i.x + vec3(0., i1.x, 1. ), pParam.xyz);

#ifndef USE_CIRCLE
        // ( N points uniformly over a line, mapped onto a diamond.)
        vec3 x = fract(p / pParam.w) ;
        vec3 h = 0.5 - abs(x) ;

        vec3 sx = vec3(lessThan(x,D.xxx)) *2. -1.;
        vec3 sh = vec3(lessThan(h,D.xxx));

        vec3 a0 = x + sx*sh;
        vec2 p0 = vec2(a0.x,h.x);
        vec2 p1 = vec2(a0.y,h.y);
        vec2 p2 = vec2(a0.z,h.z);

#ifdef NORMALISE_GRADIENTS
        p0 *= taylorInvSqrt(dot(p0,p0));
        p1 *= taylorInvSqrt(dot(p1,p1));
        p2 *= taylorInvSqrt(dot(p2,p2));
#endif

        vec3 g = 2.0 * vec3( dot(p0, x0), dot(p1, x1), dot(p2, x2) );
#else
        // N points around a unit circle.
        vec3 phi = D.z * mod(p,pParam.w) /pParam.w ;
        vec4 a0 = sin(phi.xxyy+D.xyxy);
        vec2 a1 = sin(phi.zz  +D.xy);
        vec3 g = vec3( dot(a0.xy, x0), dot(a0.zw, x1), dot(a1.xy, x2) );
#endif
        // mix
        vec3 m = max(0.5 - vec3(dot(x0,x0), dot(x1,x1), dot(x2,x2)), 0.);
        m = m*m ;
        return 1.66666* 70.*dot(m*m, g);
    }

    float simplexNoise3(vec3 v)
    {
        const vec2  C = vec2(1./6. , 1./3. ) ;
        const vec4  D = vec4(0., 0.5, 1.0, 2.0);

        // First corner
        vec3 i  = floor(v + dot(v, C.yyy) );
        vec3 x0 =   v - i + dot(i, C.xxx) ;

        // Other corners
#ifdef COLLAPSE_SORTNET
        vec3 g = vec3( greaterThan(   x0.xyz, x0.yzx) );
        vec3 l = vec3( lessThanEqual( x0.xyz, x0.yzx) );

        vec3 i1 = g.xyz  * l.zxy;
        vec3 i2 = max( g.xyz, l.zxy);
#else
        // Keeping this clean - let the compiler optimize.
        vec3 q1;
        q1.x = max(x0.x, x0.y);
        q1.y = min(x0.x, x0.y);
        q1.z = x0.z;

        vec3 q2;
        q2.x = max(q1.x,q1.z);
        q2.z = min(q1.x,q1.z);
        q2.y = q1.y;

        vec3 q3;
        q3.y = max(q2.y, q2.z);
        q3.z = min(q2.y, q2.z);
        q3.x = q2.x;

        vec3 i1 = vec3(equal(q3.xxx, x0));
        vec3 i2 = i1 + vec3(equal(q3.yyy, x0));
#endif

        //  x0 = x0 - 0. + 0. * C
        vec3 x1 = x0 - i1 + 1. * C.xxx;
        vec3 x2 = x0 - i2 + 2. * C.xxx;
        vec3 x3 = x0 - 1. + 3. * C.xxx;

        // Permutations
        i = mod(i, pParam.x );
        vec4 p = permute( permute( permute(
                                           i.z + vec4(0., i1.z, i2.z, 1. ), pParam.xyz)
                                  + i.y + vec4(0., i1.y, i2.y, 1. ), pParam.xyz)
                         + i.x + vec4(0., i1.x, i2.x, 1. ), pParam.xyz);

        // Gradients
        // ( N*N points uniformly over a square, mapped onto a octohedron.)
        float n_ = 1.0/pParam.w ;
        vec3  ns = n_ * D.wyz - D.xzx ;

        vec4 j = p - pParam.w*pParam.w*floor(p * ns.z *ns.z);  //  mod(p,N*N)

        vec4 x_ = floor(j * ns.z)  ;
        vec4 y_ = floor(j - pParam.w * x_ ) ;    // mod(j,N)

        vec4 x = x_ *ns.x + ns.yyyy;
        vec4 y = y_ *ns.x + ns.yyyy;
        vec4 h = 1. - abs(x) - abs(y);

        vec4 b0 = vec4( x.xy, y.xy );
        vec4 b1 = vec4( x.zw, y.zw );

        vec4 s0 = vec4(lessThan(b0,D.xxxx)) *2. -1.;
        vec4 s1 = vec4(lessThan(b1,D.xxxx)) *2. -1.;
        vec4 sh = vec4(lessThan(h, D.xxxx));

        vec4 a0 = b0.xzyw + s0.xzyw*sh.xxyy ;
        vec4 a1 = b1.xzyw + s1.xzyw*sh.zzww ;

        vec3 p0 = vec3(a0.xy,h.x);
        vec3 p1 = vec3(a0.zw,h.y);
        vec3 p2 = vec3(a1.xy,h.z);
        vec3 p3 = vec3(a1.zw,h.w);

#ifdef NORMALISE_GRADIENTS
        p0 *= taylorInvSqrt(dot(p0,p0));
        p1 *= taylorInvSqrt(dot(p1,p1));
        p2 *= taylorInvSqrt(dot(p2,p2));
        p3 *= taylorInvSqrt(dot(p3,p3));
#endif

        // Mix
        vec4 m = max(0.6 - vec4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.);
        m = m * m;
        //used to be 64.
        return 48.0 * dot( m*m, vec4( dot(p0,x0), dot(p1,x1),
                                     dot(p2,x2), dot(p3,x3) ) );
    }

    vec4 grad4(float j, vec4 ip)
    {
        const vec4 ones = vec4(1.,1.,1.,-1.);
        vec4 p,s;

        p.xyz = floor( fract (vec3(j) * ip.xyz) *pParam.w) * ip.z -1.0;
        p.w = 1.5 - dot(abs(p.xyz), ones.xyz);
        s = vec4(lessThan(p,vec4(0.)));
        p.xyz = p.xyz + (s.xyz*2.-1.) * s.www;

        return p;
    }

    float simplexNoise4(vec4 v)
    {
        const vec2  C = vec2( 0.138196601125010504,
                             0.309016994374947451);
        // First corner
        vec4 i  = floor(v + dot(v, C.yyyy) );
        vec4 x0 = v -   i + dot(i, C.xxxx);

        // Other corners

        // Force existance of strict total ordering in sort.
        vec4 q0 = floor(x0 * 1024.0) + vec4( 0., 1./4., 2./4. , 3./4.);
        vec4 q1;
        q1.xy = max(q0.xy,q0.zw);   //  x:z  y:w
        q1.zw = min(q0.xy,q0.zw);

        vec4 q2;
        q2.xz = max(q1.xz,q1.yw);   //  x:y  z:w
        q2.yw = min(q1.xz,q1.yw);

        vec4 q3;
        q3.y = max(q2.y,q2.z);      //  y:z
        q3.z = min(q2.y,q2.z);
        q3.xw = q2.xw;

        vec4 i1 = vec4(lessThanEqual(q3.xxxx, q0));
        vec4 i2 = vec4(lessThanEqual(q3.yyyy, q0));
        vec4 i3 = vec4(lessThanEqual(q3.zzzz, q0));

        //  x0 = x0 - 0. + 0. * C
        vec4 x1 = x0 - i1 + 1. * C.xxxx;
        vec4 x2 = x0 - i2 + 2. * C.xxxx;
        vec4 x3 = x0 - i3 + 3. * C.xxxx;
        vec4 x4 = x0 - 1. + 4. * C.xxxx;

        // Permutations
        i = mod(i, pParam.x );
        float j0 = permute( permute( permute( permute (
                                                       i.w, pParam.xyz) + i.z, pParam.xyz)
                                    + i.y, pParam.xyz) + i.x, pParam.xyz);
        vec4 j1 = permute( permute( permute( permute (
                                                      i.w + vec4(i1.w, i2.w, i3.w, 1. ), pParam.xyz)
                                            + i.z + vec4(i1.z, i2.z, i3.z, 1. ), pParam.xyz)
                                   + i.y + vec4(i1.y, i2.y, i3.y, 1. ), pParam.xyz)
                          + i.x + vec4(i1.x, i2.x, i3.x, 1. ), pParam.xyz);
        // Gradients
        // ( N*N*N points uniformly over a cube,
        // mapped onto a 4-octohedron.)
        vec4 ip = pParam ;
        ip.xy *= pParam.w ;
        ip.x  *= pParam.w ;
        ip = vec4(1.,1.,1.,2.) / ip ;

        vec4 p0 = grad4(j0,   ip);
        vec4 p1 = grad4(j1.x, ip);
        vec4 p2 = grad4(j1.y, ip);
        vec4 p3 = grad4(j1.z, ip);
        vec4 p4 = grad4(j1.w, ip);

#ifdef NORMALISE_GRADIENTS
        p0 *= taylorInvSqrt(dot(p0,p0));
        p1 *= taylorInvSqrt(dot(p1,p1));
        p2 *= taylorInvSqrt(dot(p2,p2));
        p3 *= taylorInvSqrt(dot(p3,p3));
        p4 *= taylorInvSqrt(dot(p4,p4));
#endif

        // Mix
        vec3 m0 = max(0.6 - vec3(dot(x0,x0), dot(x1,x1), dot(x2,x2)), 0.);
        vec2 m1 = max(0.6 - vec2(dot(x3,x3), dot(x4,x4)            ), 0.);
        m0 = m0 * m0;
        m1 = m1 * m1;
        return 32. * (dot(m0*m0, vec3(dot(p0, x0), dot(p1, x1), dot(p2, x2)))
                      + dot(m1*m1, vec2(dot(p3, x3), dot(p4, x4)))) ;

    }

float v3n1(vec3 v) {
	return simplexNoise3(v);
}

vec3 v3n3(vec3 v) {
    float n0 = simplexNoise3(v * 0.01);
    float n1 = simplexNoise3(v * 0.0123 + vec3(100.0));
    float n2 = simplexNoise3(v * 0.0134 + vec3(200.0));
    return vec3(n0, n1, n2);
}

vec2 v2n2(vec2 v) {
    float n0 = simplexNoise2(v * 0.01);
    float n1 = simplexNoise2(v * 0.0123 + vec2(100.0));
    return vec2(n0, n1);
}
`

const vert = `
varying vec2 vUv;
varying vec3 vNormal;

void main()
{
    vNormal = normalize(normalMatrix * normal);
    vUv = uv;
    vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );
    gl_Position = projectionMatrix * mvPosition;
}`;

const advectionFrag = `
uniform vec2 res;
uniform float speed;
uniform sampler2D tex;
varying vec2 vUv;
varying vec3 vNormal;

vec2 wrap(vec2 v) {
    return vec2(fract(v.x), fract(v.y));
}

void main()
{
    vec2 vel = texture(tex, wrap(vUv)).xy;
    vec4 color = texture(tex, wrap(vUv + vel * speed / res));
    gl_FragColor = color;
}`

const divergenceFrag = `
uniform vec2 res;
uniform float speed;
uniform sampler2D tex;
varying vec2 vUv;
varying vec3 vNormal;

vec2 wrap(vec2 v) {
    return vec2(fract(v.x), fract(v.y));
}

vec2 u(vec2 coord) {
    return texture(tex, wrap(coord)).xy;
}

void main()
{
    float rho = 1.0;
    float deltaT = 1.0 / 60.0;
    vec3 px = vec3(1.0 / res.x, 1.0 / res.y, 0.0) * speed;

    float divergence = 
        (px.x * rho / deltaT) * 
        (
            (u(vUv - px.xz).x -
            u(vUv + px.xz).x)
            +
            (u(vUv - px.zy).y -
            u(vUv + px.zy).y)
        );

    gl_FragColor = vec4(divergence , 0.0, 0.0, 1.0);
}`

const forceInitFrag = noise + `

uniform float seed;
uniform vec2 res;
varying vec2 vUv;
varying vec3 vNormal;

void main() {
	float n0 = seed + 12.3;
	float n1 = seed + 123.4;
	float n2 = seed + 1234.5;

	vec2 v0 = vUv * res / 1111.5;
	vec2 v1 = vUv * res / 1124.0;
	vec2 v2 = vUv * res / 1136.0;

	float nr = (v3n1(vec3(v0, n0)) + v3n1(vec3(v1, n1)) + v3n1(vec3(v2, n2)));
	float ng = (v3n1(vec3(v0, n1)) + v3n1(vec3(v1, n2)) + v3n1(vec3(v2, n0)));

	gl_FragColor = vec4(nr, ng, 0.0, 1.0);
}
`

const forceRenderFrag = `
varying vec2 vUv;
varying vec3 vNormal;

uniform sampler2D tex;

void main( void ) {
  gl_FragColor = texture(tex, vUv);
}`;

const forceUpdateFrag = `
uniform vec2 res;
uniform float speed;
uniform sampler2D pressure;
uniform sampler2D advection;

varying vec2 vUv;
varying vec3 vNormal;

vec2 wrap(vec2 v) {
    return vec2(fract(v.x), fract(v.y));
}

float p(vec2 coord) {
    return texture(pressure, wrap(coord)).x;
}

void main()
{
    float deltaT = 1.0 / 60.0;
    float rho = 0.999;
    vec3 px = vec3(1.0 / res.x, 1.0 / res.y, 0.0) * speed;
    vec4 u_a = texture(advection, vUv);
    
    float diff_p_x = (p(vUv + px.xz) - p(vUv - px.xz));
    float u_x = u_a.x - deltaT / (2.0 * rho * px.x) * diff_p_x;
    float diff_p_y = (p(vUv + px.zy) - p(vUv - px.zy));
    float u_y = u_a.y - deltaT / (2.0 * rho * px.y) * diff_p_y;
    u_a = vec4(vec2(u_x, u_y) * 1.0, 0.0, 1.0);

    gl_FragColor = u_a;
}
`

const pressureFrag = noise + `
uniform vec2 res;
uniform float speed;
uniform sampler2D tex;
uniform sampler2D divergence;

varying vec2 vUv;
varying vec3 vNormal;

vec2 wrap(vec2 v) {
    return vec2(fract(v.x), fract(v.y));
}

float d(vec2 coord) {
    return texture(divergence, wrap(coord)).x;
}

float p(vec2 coord) {
    return texture(tex, wrap(coord)).x;
}

void main() {
    vec3 px = vec3(1.0 / res.x, 1.0 / res.y, 0.0) * speed;

    float pressure = 0.25 * (d(vUv)
    + p(vUv + px.xz)
    + p(vUv - px.xz)
    + p(vUv + px.zy)
    + p(vUv - px.zy)
    );

    gl_FragColor = vec4(vec3(pressure), 1.0);
}
`

const paintInitFrag = noise + `
uniform float seed;
uniform vec2 res;
varying vec2 vUv;
varying vec3 vNormal;

void main() {

	float n0 = seed + 12.3;
	float n1 = seed + 123.4;
	float n2 = seed + 1234.5;

	vec2 v0 = vUv * res / 1234.5;
	vec2 v1 = vUv * res / 2345.0;
	vec2 v2 = vUv * res / 3456.0;

	float nr = v3n1(vec3(v0, n0)) + v3n1(vec3(v1, n2)) + v3n1(vec3(v2, n1));
	float ng = v3n1(vec3(v1, n1)) + v3n1(vec3(v2, n0)) + v3n1(vec3(v0, n2));
	float nb = v3n1(vec3(v2, n2)) + v3n1(vec3(v0, n1)) + v3n1(vec3(v1, n0));
	vec4 color = vUv.x < 0.5 ? vec4(1.0, 0.2, 0.0, 1.0) : vec4(0.0, 0.5, 1.0, 1.0);
	color.rgb += vec3(nr, ng, nb);
	gl_FragColor = color;
}
`

const paintRenderFrag = `
varying vec2 vUv;
varying vec3 vNormal;
uniform vec2 res;
uniform sampler2D tex;

vec2 wrap(vec2 v) {
  return vec2(fract(v.x), fract(v.y));
}

void main( void ) {
  vec3 px = vec3(1.0 / res.x, 1.0 / res.y, 0.0);
  vec4 pu = texture(tex, vUv);
  vec4 p = texture(tex, wrap(vUv + px.yz));
  //float d = (p.r + p.g + p.b) - (pu.r + pu.g + pu.b);

  vec4 color = p;
  color.r += p.r - pu.r;
  color.g += p.g - pu.g;
  color.b += p.b - pu.b;

  gl_FragColor = color;
}`;

const paintUpdateFrag = `
uniform vec2 res;
uniform float speed;
uniform sampler2D tex;
uniform sampler2D velocity;

varying vec2 vUv;
varying vec3 vNormal;

vec2 wrap(vec2 v) {
    return vec2(fract(v.x), fract(v.y));
}

void main()
{
    vec3 px = vec3(1.0 / res.x, 1.0 / res.y, 0.0) * speed;
    vec4 v = texture(velocity, vUv);
    vec4 p = texture(tex, wrap(vUv + px.xy * v.xy));

    gl_FragColor = p;
}
`

// START

init();
animate();
              
            
!
999px

Console