A CodePen by nightson.

index.html

<canvas id="sakura"></canvas>
<div class="btnbg">
<button type="button" onclick="toggleAnimation(this)">Stop</button>
</div>

<!-- sakura shader -->
<script id="sakura_point_vsh" type="x-shader/x_vertex">
uniform mat4 uProjection;
uniform mat4 uModelview;
uniform vec3 uResolution;
uniform vec3 uOffset;
uniform vec3 uDOF;  //x:focus distance, y:focus radius, z:max radius
uniform vec3 uFade; //x:start distance, y:half distance, z:near fade start

attribute vec3 aPosition;
attribute vec3 aEuler;
attribute vec2 aMisc; //x:size, y:fade

varying vec3 pposition;
varying float psize;
varying float palpha;
varying float pdist;

//varying mat3 rotMat;
varying vec3 normX;
varying vec3 normY;
varying vec3 normZ;
varying vec3 normal;

varying float diffuse;
varying float specular;
varying float rstop;
varying float distancefade;

void main(void) {
    // Projection is based on vertical angle
    vec4 pos = uModelview * vec4(aPosition + uOffset, 1.0);
    gl_Position = uProjection * pos;
    gl_PointSize = aMisc.x * uProjection[1][1] / -pos.z * uResolution.y * 0.5;
    
    pposition = pos.xyz;
    psize = aMisc.x;
    pdist = length(pos.xyz);
    palpha = smoothstep(0.0, 1.0, (pdist - 0.1) / uFade.z);
    
    vec3 elrsn = sin(aEuler);
    vec3 elrcs = cos(aEuler);
    mat3 rotx = mat3(
        1.0, 0.0, 0.0,
        0.0, elrcs.x, elrsn.x,
        0.0, -elrsn.x, elrcs.x
    );
    mat3 roty = mat3(
        elrcs.y, 0.0, -elrsn.y,
        0.0, 1.0, 0.0,
        elrsn.y, 0.0, elrcs.y
    );
    mat3 rotz = mat3(
        elrcs.z, elrsn.z, 0.0, 
        -elrsn.z, elrcs.z, 0.0,
        0.0, 0.0, 1.0
    );
    mat3 rotmat = rotx * roty * rotz;
    normal = rotmat[2];
    
    mat3 trrotm = mat3(
        rotmat[0][0], rotmat[1][0], rotmat[2][0],
        rotmat[0][1], rotmat[1][1], rotmat[2][1],
        rotmat[0][2], rotmat[1][2], rotmat[2][2]
    );
    normX = trrotm[0];
    normY = trrotm[1];
    normZ = trrotm[2];
    
    const vec3 lit = vec3(0.6917144638660746, 0.6917144638660746, -0.20751433915982237);
    
    float tmpdfs = dot(lit, normal);
    if(tmpdfs < 0.0) {
        normal = -normal;
        tmpdfs = dot(lit, normal);
    }
    diffuse = 0.4 + tmpdfs;
    
    vec3 eyev = normalize(-pos.xyz);
    if(dot(eyev, normal) > 0.0) {
        vec3 hv = normalize(eyev + lit);
        specular = pow(max(dot(hv, normal), 0.0), 20.0);
    }
    else {
        specular = 0.0;
    }
    
    rstop = clamp((abs(pdist - uDOF.x) - uDOF.y) / uDOF.z, 0.0, 1.0);
    rstop = pow(rstop, 0.5);
    //-0.69315 = ln(0.5)
    distancefade = min(1.0, exp((uFade.x - pdist) * 0.69315 / uFade.y));
}
</script>
<script id="sakura_point_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif

uniform vec3 uDOF;  //x:focus distance, y:focus radius, z:max radius
uniform vec3 uFade; //x:start distance, y:half distance, z:near fade start

const vec3 fadeCol = vec3(0.08, 0.03, 0.06);

varying vec3 pposition;
varying float psize;
varying float palpha;
varying float pdist;

//varying mat3 rotMat;
varying vec3 normX;
varying vec3 normY;
varying vec3 normZ;
varying vec3 normal;

varying float diffuse;
varying float specular;
varying float rstop;
varying float distancefade;

float ellipse(vec2 p, vec2 o, vec2 r) {
    vec2 lp = (p - o) / r;
    return length(lp) - 1.0;
}

void main(void) {
    vec3 p = vec3(gl_PointCoord - vec2(0.5, 0.5), 0.0) * 2.0;
    vec3 d = vec3(0.0, 0.0, -1.0);
    float nd = normZ.z; //dot(-normZ, d);
    if(abs(nd) < 0.0001) discard;
    
    float np = dot(normZ, p);
    vec3 tp = p + d * np / nd;
    vec2 coord = vec2(dot(normX, tp), dot(normY, tp));
    
    //angle = 15 degree
    const float flwrsn = 0.258819045102521;
    const float flwrcs = 0.965925826289068;
    mat2 flwrm = mat2(flwrcs, -flwrsn, flwrsn, flwrcs);
    vec2 flwrp = vec2(abs(coord.x), coord.y) * flwrm;
    
    float r;
    if(flwrp.x < 0.0) {
        r = ellipse(flwrp, vec2(0.065, 0.024) * 0.5, vec2(0.36, 0.96) * 0.5);
    }
    else {
        r = ellipse(flwrp, vec2(0.065, 0.024) * 0.5, vec2(0.58, 0.96) * 0.5);
    }
    
    if(r > rstop) discard;
    
    vec3 col = mix(vec3(1.0, 0.8, 0.75), vec3(1.0, 0.9, 0.87), r);
    float grady = mix(0.0, 1.0, pow(coord.y * 0.5 + 0.5, 0.35));
    col *= vec3(1.0, grady, grady);
    col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3));
    col = col * diffuse + specular;
    
    col = mix(fadeCol, col, distancefade);
    
    float alpha = (rstop > 0.001)? (0.5 - r / (rstop * 2.0)) : 1.0;
    alpha = smoothstep(0.0, 1.0, alpha) * palpha;
    
    gl_FragColor = vec4(col * 0.5, alpha);
}
</script>
<!-- effects -->
<script id="fx_common_vsh" type="x-shader/x_vertex">
uniform vec3 uResolution;
attribute vec2 aPosition;

varying vec2 texCoord;
varying vec2 screenCoord;

void main(void) {
    gl_Position = vec4(aPosition, 0.0, 1.0);
    texCoord = aPosition.xy * 0.5 + vec2(0.5, 0.5);
    screenCoord = aPosition.xy * vec2(uResolution.z, 1.0);
}
</script>
<script id="bg_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif

uniform vec2 uTimes;

varying vec2 texCoord;
varying vec2 screenCoord;

void main(void) {
    vec3 col;
    float c;
    vec2 tmpv = texCoord * vec2(0.8, 1.0) - vec2(0.95, 1.0);
    c = exp(-pow(length(tmpv) * 1.8, 2.0));
    col = mix(vec3(0.02, 0.0, 0.03), vec3(0.96, 0.98, 1.0) * 1.5, c);
    gl_FragColor = vec4(col * 0.5, 1.0);
}
</script>
<script id="fx_brightbuf_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif
uniform sampler2D uSrc;
uniform vec2 uDelta;

varying vec2 texCoord;
varying vec2 screenCoord;

void main(void) {
    vec4 col = texture2D(uSrc, texCoord);
    gl_FragColor = vec4(col.rgb * 2.0 - vec3(0.5), 1.0);
}
</script>
<script id="fx_dirblur_r4_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif
uniform sampler2D uSrc;
uniform vec2 uDelta;
uniform vec4 uBlurDir; //dir(x, y), stride(z, w)

varying vec2 texCoord;
varying vec2 screenCoord;

void main(void) {
    vec4 col = texture2D(uSrc, texCoord);
    col = col + texture2D(uSrc, texCoord + uBlurDir.xy * uDelta);
    col = col + texture2D(uSrc, texCoord - uBlurDir.xy * uDelta);
    col = col + texture2D(uSrc, texCoord + (uBlurDir.xy + uBlurDir.zw) * uDelta);
    col = col + texture2D(uSrc, texCoord - (uBlurDir.xy + uBlurDir.zw) * uDelta);
    gl_FragColor = col / 5.0;
}
</script>
<!-- effect fragment shader template -->
<script id="fx_common_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif
uniform sampler2D uSrc;
uniform vec2 uDelta;

varying vec2 texCoord;
varying vec2 screenCoord;

void main(void) {
    gl_FragColor = texture2D(uSrc, texCoord);
}
</script>
<!-- post processing -->
<script id="pp_final_vsh" type="x-shader/x_vertex">
uniform vec3 uResolution;
attribute vec2 aPosition;
varying vec2 texCoord;
varying vec2 screenCoord;
void main(void) {
    gl_Position = vec4(aPosition, 0.0, 1.0);
    texCoord = aPosition.xy * 0.5 + vec2(0.5, 0.5);
    screenCoord = aPosition.xy * vec2(uResolution.z, 1.0);
}
</script>
<script id="pp_final_fsh" type="x-shader/x_fragment">
#ifdef GL_ES
//precision mediump float;
precision highp float;
#endif
uniform sampler2D uSrc;
uniform sampler2D uBloom;
uniform vec2 uDelta;
varying vec2 texCoord;
varying vec2 screenCoord;
void main(void) {
    vec4 srccol = texture2D(uSrc, texCoord) * 2.0;
    vec4 bloomcol = texture2D(uBloom, texCoord);
    vec4 col;
    col = srccol + bloomcol * (vec4(1.0) + srccol);
    col *= smoothstep(1.0, 0.0, pow(length((texCoord - vec2(0.5)) * 2.0), 1.2) * 0.5);
    col = pow(col, vec4(0.45454545454545)); //(1.0 / 2.2)
    
    gl_FragColor = vec4(col.rgb, 1.0);
    gl_FragColor.a = 1.0;
}
</script>

script.js

// Utilities
var Vector3 = {};
var Matrix44 = {};
Vector3.create = function(x, y, z) {
    return {'x':x, 'y':y, 'z':z};
};
Vector3.dot = function (v0, v1) {
    return v0.x * v1.x + v0.y * v1.y + v0.z * v1.z;
};
Vector3.cross = function (v, v0, v1) {
    v.x = v0.y * v1.z - v0.z * v1.y;
    v.y = v0.z * v1.x - v0.x * v1.z;
    v.z = v0.x * v1.y - v0.y * v1.x;
};
Vector3.normalize = function (v) {
    var l = v.x * v.x + v.y * v.y + v.z * v.z;
    if(l > 0.00001) {
        l = 1.0 / Math.sqrt(l);
        v.x *= l;
        v.y *= l;
        v.z *= l;
    }
};
Vector3.arrayForm = function(v) {
    if(v.array) {
        v.array[0] = v.x;
        v.array[1] = v.y;
        v.array[2] = v.z;
    }
    else {
        v.array = new Float32Array([v.x, v.y, v.z]);
    }
    return v.array;
};
Matrix44.createIdentity = function () {
    return new Float32Array([1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0]);
};
Matrix44.loadProjection = function (m, aspect, vdeg, near, far) {
    var h = near * Math.tan(vdeg * Math.PI / 180.0 * 0.5) * 2.0;
    var w = h * aspect;
    
    m[0] = 2.0 * near / w;
    m[1] = 0.0;
    m[2] = 0.0;
    m[3] = 0.0;
    
    m[4] = 0.0;
    m[5] = 2.0 * near / h;
    m[6] = 0.0;
    m[7] = 0.0;
    
    m[8] = 0.0;
    m[9] = 0.0;
    m[10] = -(far + near) / (far - near);
    m[11] = -1.0;
    
    m[12] = 0.0;
    m[13] = 0.0;
    m[14] = -2.0 * far * near / (far - near);
    m[15] = 0.0;
};
Matrix44.loadLookAt = function (m, vpos, vlook, vup) {
    var frontv = Vector3.create(vpos.x - vlook.x, vpos.y - vlook.y, vpos.z - vlook.z);
    Vector3.normalize(frontv);
    var sidev = Vector3.create(1.0, 0.0, 0.0);
    Vector3.cross(sidev, vup, frontv);
    Vector3.normalize(sidev);
    var topv = Vector3.create(1.0, 0.0, 0.0);
    Vector3.cross(topv, frontv, sidev);
    Vector3.normalize(topv);
    
    m[0] = sidev.x;
    m[1] = topv.x;
    m[2] = frontv.x;
    m[3] = 0.0;
    
    m[4] = sidev.y;
    m[5] = topv.y;
    m[6] = frontv.y;
    m[7] = 0.0;
    
    m[8] = sidev.z;
    m[9] = topv.z;
    m[10] = frontv.z;
    m[11] = 0.0;
    
    m[12] = -(vpos.x * m[0] + vpos.y * m[4] + vpos.z * m[8]);
    m[13] = -(vpos.x * m[1] + vpos.y * m[5] + vpos.z * m[9]);
    m[14] = -(vpos.x * m[2] + vpos.y * m[6] + vpos.z * m[10]);
    m[15] = 1.0;
};

//
var timeInfo = {
    'start':0, 'prev':0, // Date
    'delta':0, 'elapsed':0 // Number(sec)
};

//
var gl;
var renderSpec = {
    'width':0,
    'height':0,
    'aspect':1,
    'array':new Float32Array(3),
    'halfWidth':0,
    'halfHeight':0,
    'halfArray':new Float32Array(3)
    // and some render targets. see setViewport()
};
renderSpec.setSize = function(w, h) {
    renderSpec.width = w;
    renderSpec.height = h;
    renderSpec.aspect = renderSpec.width / renderSpec.height;
    renderSpec.array[0] = renderSpec.width;
    renderSpec.array[1] = renderSpec.height;
    renderSpec.array[2] = renderSpec.aspect;
    
    renderSpec.halfWidth = Math.floor(w / 2);
    renderSpec.halfHeight = Math.floor(h / 2);
    renderSpec.halfArray[0] = renderSpec.halfWidth;
    renderSpec.halfArray[1] = renderSpec.halfHeight;
    renderSpec.halfArray[2] = renderSpec.halfWidth / renderSpec.halfHeight;
};

function deleteRenderTarget(rt) {
    gl.deleteFramebuffer(rt.frameBuffer);
    gl.deleteRenderbuffer(rt.renderBuffer);
    gl.deleteTexture(rt.texture);
}

function createRenderTarget(w, h) {
    var ret = {
        'width':w,
        'height':h,
        'sizeArray':new Float32Array([w, h, w / h]),
        'dtxArray':new Float32Array([1.0 / w, 1.0 / h])
    };
    ret.frameBuffer = gl.createFramebuffer();
    ret.renderBuffer = gl.createRenderbuffer();
    ret.texture = gl.createTexture();
    
    gl.bindTexture(gl.TEXTURE_2D, ret.texture);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, w, h, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    
    gl.bindFramebuffer(gl.FRAMEBUFFER, ret.frameBuffer);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, ret.texture, 0);
    
    gl.bindRenderbuffer(gl.RENDERBUFFER, ret.renderBuffer);
    gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, w, h);
    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, ret.renderBuffer);
    
    gl.bindTexture(gl.TEXTURE_2D, null);
    gl.bindRenderbuffer(gl.RENDERBUFFER, null);
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
    
    return ret;
}

function compileShader(shtype, shsrc) {
	var retsh = gl.createShader(shtype);
	
	gl.shaderSource(retsh, shsrc);
	gl.compileShader(retsh);
	
	if(!gl.getShaderParameter(retsh, gl.COMPILE_STATUS)) {
		var errlog = gl.getShaderInfoLog(retsh);
		gl.deleteShader(retsh);
		console.error(errlog);
		return null;
	}
	return retsh;
}

function createShader(vtxsrc, frgsrc, uniformlist, attrlist) {
    var vsh = compileShader(gl.VERTEX_SHADER, vtxsrc);
    var fsh = compileShader(gl.FRAGMENT_SHADER, frgsrc);
    
    if(vsh == null || fsh == null) {
        return null;
    }
    
    var prog = gl.createProgram();
    gl.attachShader(prog, vsh);
    gl.attachShader(prog, fsh);
    
    gl.deleteShader(vsh);
    gl.deleteShader(fsh);
    
    gl.linkProgram(prog);
    if (!gl.getProgramParameter(prog, gl.LINK_STATUS)) {
        var errlog = gl.getProgramInfoLog(prog);
        console.error(errlog);
        return null;
    }
    
    if(uniformlist) {
        prog.uniforms = {};
        for(var i = 0; i < uniformlist.length; i++) {
            prog.uniforms[uniformlist[i]] = gl.getUniformLocation(prog, uniformlist[i]);
        }
    }
    
    if(attrlist) {
        prog.attributes = {};
        for(var i = 0; i < attrlist.length; i++) {
            var attr = attrlist[i];
            prog.attributes[attr] = gl.getAttribLocation(prog, attr);
        }
    }
    
    return prog;
}

function useShader(prog) {
    gl.useProgram(prog);
    for(var attr in prog.attributes) {
        gl.enableVertexAttribArray(prog.attributes[attr]);;
    }
}

function unuseShader(prog) {
    for(var attr in prog.attributes) {
        gl.disableVertexAttribArray(prog.attributes[attr]);;
    }
    gl.useProgram(null);
}

/////
var projection = {
    'angle':60,
    'nearfar':new Float32Array([0.1, 100.0]),
    'matrix':Matrix44.createIdentity()
};
var camera = {
    'position':Vector3.create(0, 0, 100),
    'lookat':Vector3.create(0, 0, 0),
    'up':Vector3.create(0, 1, 0),
    'dof':Vector3.create(10.0, 4.0, 8.0),
    'matrix':Matrix44.createIdentity()
};

var pointFlower = {};
var meshFlower = {};
var sceneStandBy = false;

var BlossomParticle = function () {
    this.velocity = new Array(3);
    this.rotation = new Array(3);
    this.position = new Array(3);
    this.euler = new Array(3);
    this.size = 1.0;
    this.alpha = 1.0;
    this.zkey = 0.0;
};

BlossomParticle.prototype.setVelocity = function (vx, vy, vz) {
    this.velocity[0] = vx;
    this.velocity[1] = vy;
    this.velocity[2] = vz;
};

BlossomParticle.prototype.setRotation = function (rx, ry, rz) {
    this.rotation[0] = rx;
    this.rotation[1] = ry;
    this.rotation[2] = rz;
};

BlossomParticle.prototype.setPosition = function (nx, ny, nz) {
    this.position[0] = nx;
    this.position[1] = ny;
    this.position[2] = nz;
};

BlossomParticle.prototype.setEulerAngles = function (rx, ry, rz) {
    this.euler[0] = rx;
    this.euler[1] = ry;
    this.euler[2] = rz;
};

BlossomParticle.prototype.setSize = function (s) {
    this.size = s;
};

BlossomParticle.prototype.update = function (dt, et) {
    this.position[0] += this.velocity[0] * dt;
    this.position[1] += this.velocity[1] * dt;
    this.position[2] += this.velocity[2] * dt;
    
    this.euler[0] += this.rotation[0] * dt;
    this.euler[1] += this.rotation[1] * dt;
    this.euler[2] += this.rotation[2] * dt;
};

function createPointFlowers() {
    // get point sizes
    var prm = gl.getParameter(gl.ALIASED_POINT_SIZE_RANGE);
    renderSpec.pointSize = {'min':prm[0], 'max':prm[1]};
    
    var vtxsrc = document.getElementById("sakura_point_vsh").textContent;
    var frgsrc = document.getElementById("sakura_point_fsh").textContent;
    
    pointFlower.program = createShader(
        vtxsrc, frgsrc,
        ['uProjection', 'uModelview', 'uResolution', 'uOffset', 'uDOF', 'uFade'],
        ['aPosition', 'aEuler', 'aMisc']
    );
    
    useShader(pointFlower.program);
    pointFlower.offset = new Float32Array([0.0, 0.0, 0.0]);
    pointFlower.fader = Vector3.create(0.0, 10.0, 0.0);
    
    // paramerters: velocity[3], rotate[3]
    pointFlower.numFlowers = 1600;
    pointFlower.particles = new Array(pointFlower.numFlowers);
    // vertex attributes {position[3], euler_xyz[3], size[1]}
    pointFlower.dataArray = new Float32Array(pointFlower.numFlowers * (3 + 3 + 2));
    pointFlower.positionArrayOffset = 0;
    pointFlower.eulerArrayOffset = pointFlower.numFlowers * 3;
    pointFlower.miscArrayOffset = pointFlower.numFlowers * 6;
    
    pointFlower.buffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, pointFlower.buffer);
    gl.bufferData(gl.ARRAY_BUFFER, pointFlower.dataArray, gl.DYNAMIC_DRAW);
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    
    unuseShader(pointFlower.program);
    
    for(var i = 0; i < pointFlower.numFlowers; i++) {
        pointFlower.particles[i] = new BlossomParticle();
    }
}

function initPointFlowers() {
    //area
    pointFlower.area = Vector3.create(20.0, 20.0, 20.0);
    pointFlower.area.x = pointFlower.area.y * renderSpec.aspect;
    
    pointFlower.fader.x = 10.0; //env fade start
    pointFlower.fader.y = pointFlower.area.z; //env fade half
    pointFlower.fader.z = 0.1;  //near fade start
    
    //particles
    var PI2 = Math.PI * 2.0;
    var tmpv3 = Vector3.create(0, 0, 0);
    var tmpv = 0;
    var symmetryrand = function() {return (Math.random() * 2.0 - 1.0);};
    for(var i = 0; i < pointFlower.numFlowers; i++) {
        var tmpprtcl = pointFlower.particles[i];
        
        //velocity
        tmpv3.x = symmetryrand() * 0.3 + 0.8;
        tmpv3.y = symmetryrand() * 0.2 - 1.0;
        tmpv3.z = symmetryrand() * 0.3 + 0.5;
        Vector3.normalize(tmpv3);
        tmpv = 2.0 + Math.random() * 1.0;
        tmpprtcl.setVelocity(tmpv3.x * tmpv, tmpv3.y * tmpv, tmpv3.z * tmpv);
        
        //rotation
        tmpprtcl.setRotation(
            symmetryrand() * PI2 * 0.5,
            symmetryrand() * PI2 * 0.5,
            symmetryrand() * PI2 * 0.5
        );
        
        //position
        tmpprtcl.setPosition(
            symmetryrand() * pointFlower.area.x,
            symmetryrand() * pointFlower.area.y,
            symmetryrand() * pointFlower.area.z
        );
        
        //euler
        tmpprtcl.setEulerAngles(
            Math.random() * Math.PI * 2.0,
            Math.random() * Math.PI * 2.0,
            Math.random() * Math.PI * 2.0
        );
        
        //size
        tmpprtcl.setSize(0.9 + Math.random() * 0.1);
    }
}

function renderPointFlowers() {
    //update
    var PI2 = Math.PI * 2.0;
    var limit = [pointFlower.area.x, pointFlower.area.y, pointFlower.area.z];
    var repeatPos = function (prt, cmp, limit) {
        if(Math.abs(prt.position[cmp]) - prt.size * 0.5 > limit) {
            //out of area
            if(prt.position[cmp] > 0) {
                prt.position[cmp] -= limit * 2.0;
            }
            else {
                prt.position[cmp] += limit * 2.0;
            }
        }
    };
    var repeatEuler = function (prt, cmp) {
        prt.euler[cmp] = prt.euler[cmp] % PI2;
        if(prt.euler[cmp] < 0.0) {
            prt.euler[cmp] += PI2;
        }
    };
    
    for(var i = 0; i < pointFlower.numFlowers; i++) {
        var prtcl = pointFlower.particles[i];
        prtcl.update(timeInfo.delta, timeInfo.elapsed);
        repeatPos(prtcl, 0, pointFlower.area.x);
        repeatPos(prtcl, 1, pointFlower.area.y);
        repeatPos(prtcl, 2, pointFlower.area.z);
        repeatEuler(prtcl, 0);
        repeatEuler(prtcl, 1);
        repeatEuler(prtcl, 2);
        
        prtcl.alpha = 1.0;//(pointFlower.area.z - prtcl.position[2]) * 0.5;
        
        prtcl.zkey = (camera.matrix[2] * prtcl.position[0]
                    + camera.matrix[6] * prtcl.position[1]
                    + camera.matrix[10] * prtcl.position[2]
                    + camera.matrix[14]);
    }
    
    // sort
    pointFlower.particles.sort(function(p0, p1){return p0.zkey - p1.zkey;});
    
    // update data
    var ipos = pointFlower.positionArrayOffset;
    var ieuler = pointFlower.eulerArrayOffset;
    var imisc = pointFlower.miscArrayOffset;
    for(var i = 0; i < pointFlower.numFlowers; i++) {
        var prtcl = pointFlower.particles[i];
        pointFlower.dataArray[ipos] = prtcl.position[0];
        pointFlower.dataArray[ipos + 1] = prtcl.position[1];
        pointFlower.dataArray[ipos + 2] = prtcl.position[2];
        ipos += 3;
        pointFlower.dataArray[ieuler] = prtcl.euler[0];
        pointFlower.dataArray[ieuler + 1] = prtcl.euler[1];
        pointFlower.dataArray[ieuler + 2] = prtcl.euler[2];
        ieuler += 3;
        pointFlower.dataArray[imisc] = prtcl.size;
        pointFlower.dataArray[imisc + 1] = prtcl.alpha;
        imisc += 2;
    }
    
    //draw
    gl.enable(gl.BLEND);
    //gl.disable(gl.DEPTH_TEST);
    gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);
    
    var prog = pointFlower.program;
    useShader(prog);
    
    gl.uniformMatrix4fv(prog.uniforms.uProjection, false, projection.matrix);
    gl.uniformMatrix4fv(prog.uniforms.uModelview, false, camera.matrix);
    gl.uniform3fv(prog.uniforms.uResolution, renderSpec.array);
    gl.uniform3fv(prog.uniforms.uDOF, Vector3.arrayForm(camera.dof));
    gl.uniform3fv(prog.uniforms.uFade, Vector3.arrayForm(pointFlower.fader));
    
    gl.bindBuffer(gl.ARRAY_BUFFER, pointFlower.buffer);
    gl.bufferData(gl.ARRAY_BUFFER, pointFlower.dataArray, gl.DYNAMIC_DRAW);
    
    gl.vertexAttribPointer(prog.attributes.aPosition, 3, gl.FLOAT, false, 0, pointFlower.positionArrayOffset * Float32Array.BYTES_PER_ELEMENT);
    gl.vertexAttribPointer(prog.attributes.aEuler, 3, gl.FLOAT, false, 0, pointFlower.eulerArrayOffset * Float32Array.BYTES_PER_ELEMENT);
    gl.vertexAttribPointer(prog.attributes.aMisc, 2, gl.FLOAT, false, 0, pointFlower.miscArrayOffset * Float32Array.BYTES_PER_ELEMENT);
    
    // doubler
    for(var i = 1; i < 2; i++) {
        var zpos = i * -2.0;
        pointFlower.offset[0] = pointFlower.area.x * -1.0;
        pointFlower.offset[1] = pointFlower.area.y * -1.0;
        pointFlower.offset[2] = pointFlower.area.z * zpos;
        gl.uniform3fv(prog.uniforms.uOffset, pointFlower.offset);
        gl.drawArrays(gl.POINT, 0, pointFlower.numFlowers);
        
        pointFlower.offset[0] = pointFlower.area.x * -1.0;
        pointFlower.offset[1] = pointFlower.area.y *  1.0;
        pointFlower.offset[2] = pointFlower.area.z * zpos;
        gl.uniform3fv(prog.uniforms.uOffset, pointFlower.offset);
        gl.drawArrays(gl.POINT, 0, pointFlower.numFlowers);
        
        pointFlower.offset[0] = pointFlower.area.x *  1.0;
        pointFlower.offset[1] = pointFlower.area.y * -1.0;
        pointFlower.offset[2] = pointFlower.area.z * zpos;
        gl.uniform3fv(prog.uniforms.uOffset, pointFlower.offset);
        gl.drawArrays(gl.POINT, 0, pointFlower.numFlowers);
        
        pointFlower.offset[0] = pointFlower.area.x *  1.0;
        pointFlower.offset[1] = pointFlower.area.y *  1.0;
        pointFlower.offset[2] = pointFlower.area.z * zpos;
        gl.uniform3fv(prog.uniforms.uOffset, pointFlower.offset);
        gl.drawArrays(gl.POINT, 0, pointFlower.numFlowers);
    }
    
    //main
    pointFlower.offset[0] = 0.0;
    pointFlower.offset[1] = 0.0;
    pointFlower.offset[2] = 0.0;
    gl.uniform3fv(prog.uniforms.uOffset, pointFlower.offset);
    gl.drawArrays(gl.POINT, 0, pointFlower.numFlowers);
    
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    unuseShader(prog);
    
    gl.enable(gl.DEPTH_TEST);
    gl.disable(gl.BLEND);
}

// effects
//common util
function createEffectProgram(vtxsrc, frgsrc, exunifs, exattrs) {
    var ret = {};
    var unifs = ['uResolution', 'uSrc', 'uDelta'];
    if(exunifs) {
        unifs = unifs.concat(exunifs);
    }
    var attrs = ['aPosition'];
    if(exattrs) {
        attrs = attrs.concat(exattrs);
    }
    
    ret.program = createShader(vtxsrc, frgsrc, unifs, attrs);
    useShader(ret.program);
    
    ret.dataArray = new Float32Array([
        -1.0, -1.0,
         1.0, -1.0,
        -1.0,  1.0,
         1.0,  1.0
    ]);
    ret.buffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, ret.buffer);
    gl.bufferData(gl.ARRAY_BUFFER, ret.dataArray, gl.STATIC_DRAW);
    
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    unuseShader(ret.program);
    
    return ret;
}

// basic usage
// useEffect(prog, srctex({'texture':texid, 'dtxArray':(f32)[dtx, dty]})); //basic initialize
// gl.uniform**(...); //additional uniforms
// drawEffect()
// unuseEffect(prog)
// TEXTURE0 makes src
function useEffect(fxobj, srctex) {
    var prog = fxobj.program;
    useShader(prog);
    gl.uniform3fv(prog.uniforms.uResolution, renderSpec.array);
    
    if(srctex != null) {
        gl.uniform2fv(prog.uniforms.uDelta, srctex.dtxArray);
        gl.uniform1i(prog.uniforms.uSrc, 0);
        
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, srctex.texture);
    }
}
function drawEffect(fxobj) {
    gl.bindBuffer(gl.ARRAY_BUFFER, fxobj.buffer);
    gl.vertexAttribPointer(fxobj.program.attributes.aPosition, 2, gl.FLOAT, false, 0, 0);
    gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
}
function unuseEffect(fxobj) {
    unuseShader(fxobj.program);
}

var effectLib = {};
function createEffectLib() {
    
    var vtxsrc, frgsrc;
    //common
    var cmnvtxsrc = document.getElementById("fx_common_vsh").textContent;
    
    //background
    frgsrc = document.getElementById("bg_fsh").textContent;
    effectLib.sceneBg = createEffectProgram(cmnvtxsrc, frgsrc, ['uTimes'], null);
    
    // make brightpixels buffer
    frgsrc = document.getElementById("fx_brightbuf_fsh").textContent;
    effectLib.mkBrightBuf = createEffectProgram(cmnvtxsrc, frgsrc, null, null);
    
    // direction blur
    frgsrc = document.getElementById("fx_dirblur_r4_fsh").textContent;
    effectLib.dirBlur = createEffectProgram(cmnvtxsrc, frgsrc, ['uBlurDir'], null);
    
    //final composite
    vtxsrc = document.getElementById("pp_final_vsh").textContent;
    frgsrc = document.getElementById("pp_final_fsh").textContent;
    effectLib.finalComp = createEffectProgram(vtxsrc, frgsrc, ['uBloom'], null);
}

// background
function createBackground() {
    //console.log("create background");
}
function initBackground() {
    //console.log("init background");
}
function renderBackground() {
    gl.disable(gl.DEPTH_TEST);
    
    useEffect(effectLib.sceneBg, null);
    gl.uniform2f(effectLib.sceneBg.program.uniforms.uTimes, timeInfo.elapsed, timeInfo.delta);
    drawEffect(effectLib.sceneBg);
    unuseEffect(effectLib.sceneBg);
    
    gl.enable(gl.DEPTH_TEST);
}

// post process
var postProcess = {};
function createPostProcess() {
    //console.log("create post process");
}
function initPostProcess() {
    //console.log("init post process");
}

function renderPostProcess() {
    gl.enable(gl.TEXTURE_2D);
    gl.disable(gl.DEPTH_TEST);
    var bindRT = function (rt, isclear) {
        gl.bindFramebuffer(gl.FRAMEBUFFER, rt.frameBuffer);
        gl.viewport(0, 0, rt.width, rt.height);
        if(isclear) {
            gl.clearColor(0, 0, 0, 0);
            gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
        }
    };
    
    //make bright buff
    bindRT(renderSpec.wHalfRT0, true);
    useEffect(effectLib.mkBrightBuf, renderSpec.mainRT);
    drawEffect(effectLib.mkBrightBuf);
    unuseEffect(effectLib.mkBrightBuf);
    
    // make bloom
    for(var i = 0; i < 2; i++) {
        var p = 1.5 + 1 * i;
        var s = 2.0 + 1 * i;
        bindRT(renderSpec.wHalfRT1, true);
        useEffect(effectLib.dirBlur, renderSpec.wHalfRT0);
        gl.uniform4f(effectLib.dirBlur.program.uniforms.uBlurDir, p, 0.0, s, 0.0);
        drawEffect(effectLib.dirBlur);
        unuseEffect(effectLib.dirBlur);
        
        bindRT(renderSpec.wHalfRT0, true);
        useEffect(effectLib.dirBlur, renderSpec.wHalfRT1);
        gl.uniform4f(effectLib.dirBlur.program.uniforms.uBlurDir, 0.0, p, 0.0, s);
        drawEffect(effectLib.dirBlur);
        unuseEffect(effectLib.dirBlur);
    }
    
    //display
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
    gl.viewport(0, 0, renderSpec.width, renderSpec.height);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    
    useEffect(effectLib.finalComp, renderSpec.mainRT);
    gl.uniform1i(effectLib.finalComp.program.uniforms.uBloom, 1);
    gl.activeTexture(gl.TEXTURE1);
    gl.bindTexture(gl.TEXTURE_2D, renderSpec.wHalfRT0.texture);
    drawEffect(effectLib.finalComp);
    unuseEffect(effectLib.finalComp);
    
    gl.enable(gl.DEPTH_TEST);
}

/////
var SceneEnv = {};
function createScene() {
    createEffectLib();
    createBackground();
    createPointFlowers();
    createPostProcess();
    sceneStandBy = true;
}

function initScene() {
    initBackground();
    initPointFlowers();
    initPostProcess();
    
    //camera.position.z = 17.320508;
    camera.position.z = pointFlower.area.z + projection.nearfar[0];
    projection.angle = Math.atan2(pointFlower.area.y, camera.position.z + pointFlower.area.z) * 180.0 / Math.PI * 2.0;
    Matrix44.loadProjection(projection.matrix, renderSpec.aspect, projection.angle, projection.nearfar[0], projection.nearfar[1]);
}

function renderScene() {
    //draw
    Matrix44.loadLookAt(camera.matrix, camera.position, camera.lookat, camera.up);
    
    gl.enable(gl.DEPTH_TEST);
    
    //gl.bindFramebuffer(gl.FRAMEBUFFER, null);
    gl.bindFramebuffer(gl.FRAMEBUFFER, renderSpec.mainRT.frameBuffer);
    gl.viewport(0, 0, renderSpec.mainRT.width, renderSpec.mainRT.height);
    gl.clearColor(0.005, 0, 0.05, 0);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    
    renderBackground();
    renderPointFlowers();
    renderPostProcess();
}

/////
function onResize(e) {
    makeCanvasFullScreen(document.getElementById("sakura"));
    setViewports();
    if(sceneStandBy) {
        initScene();
    }
}

function setViewports() {
    renderSpec.setSize(gl.canvas.width, gl.canvas.height);
    
    gl.clearColor(0.2, 0.2, 0.5, 1.0);
    gl.viewport(0, 0, renderSpec.width, renderSpec.height);
    
    var rtfunc = function (rtname, rtw, rth) {
        var rt = renderSpec[rtname];
        if(rt) deleteRenderTarget(rt);
        renderSpec[rtname] = createRenderTarget(rtw, rth);
    };
    rtfunc('mainRT', renderSpec.width, renderSpec.height);
    rtfunc('wFullRT0', renderSpec.width, renderSpec.height);
    rtfunc('wFullRT1', renderSpec.width, renderSpec.height);
    rtfunc('wHalfRT0', renderSpec.halfWidth, renderSpec.halfHeight);
    rtfunc('wHalfRT1', renderSpec.halfWidth, renderSpec.halfHeight);
}

function render() {
    renderScene();
}

var animating = true;
function toggleAnimation(elm) {
    animating ^= true;
    if(animating) animate();
    if(elm) {
        elm.innerHTML = animating? "Stop":"Start";
    }
}

function stepAnimation() {
    if(!animating) animate();
}

function animate() {
    var curdate = new Date();
    timeInfo.elapsed = (curdate - timeInfo.start) / 1000.0;
    timeInfo.delta = (curdate - timeInfo.prev) / 1000.0;
    timeInfo.prev = curdate;
    
    if(animating) requestAnimationFrame(animate);
    render();
}

function makeCanvasFullScreen(canvas) {
    var b = document.body;
	var d = document.documentElement;
	fullw = Math.max(b.clientWidth , b.scrollWidth, d.scrollWidth, d.clientWidth);
	fullh = Math.max(b.clientHeight , b.scrollHeight, d.scrollHeight, d.clientHeight);
	canvas.width = fullw;
	canvas.height = fullh;
}

window.addEventListener('load', function(e) {
    var canvas = document.getElementById("sakura");
    try {
        makeCanvasFullScreen(canvas);
        gl = canvas.getContext('experimental-webgl');
    } catch(e) {
        alert("WebGL not supported." + e);
        console.error(e);
        return;
    }
    
    window.addEventListener('resize', onResize);
    
    setViewports();
    createScene();
    initScene();
    
    timeInfo.start = new Date();
    timeInfo.prev = timeInfo.start;
    animate();
});

//set window.requestAnimationFrame
(function (w, r) {
    w['r'+r] = w['r'+r] || w['webkitR'+r] || w['mozR'+r] || w['msR'+r] || w['oR'+r] || function(c){ w.setTimeout(c, 1000 / 60); };
})(window, 'equestAnimationFrame');

style.css

body {
    padding:0;
    margin:0;
    overflow:hidden;
	height: 600px;
}
canvas {
    padding:0;
    margin:0;
}
div.btnbg {
    position:fixed;
    left:0;
    top:0;
}