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SerenaRed.html
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<!-- saved from url=(0053)https://www.ibiblio.org/e-notes/webgl/gpu/droplet.htm -->
<html class="gr__ibiblio_org"><head><meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<!-- gl_FragColor = vec4(rg, rg, 1. + rg, 1.); -->
<title>2D ink droplet</title>
<script id="shader-fs-show" type="x-shader/x-fragment">
precision highp float;
uniform sampler2D samp;
varying vec2 tc;
void main(void) {
gl_FragColor = texture2D(samp, tc) + 1.0;
// float rg = 1. + texture2D(samp, tc).b;
//gl_FragColor = vec4(1. + rg, 0.2 + rg, rg, 1.); //color
}
</script>
<script id="advec-fs" type="x-shader/x-fragment">
precision highp float;
uniform sampler2D samp;
varying vec2 tc;
const float h = 1./512., dt = .001, tau = .5*dt/h;
void main(void) {
vec2 D = -tau*vec2(
texture2D(samp, tc).r + texture2D(samp, vec2(tc.r - h, tc.g)).r,
texture2D(samp, tc).g + texture2D(samp, vec2(tc.r, tc.g - h)).g );
vec2 Df = floor(D), Dd = D - Df;
vec2 tc1 = tc + Df*h;
vec3 new =
(texture2D(samp, tc1).rgb*(1. - Dd.g) +
texture2D(samp, vec2(tc1.r, tc1.g + h)).rgb*Dd.g)*(1. - Dd.r) +
(texture2D(samp, vec2(tc1.r + h, tc1.g)).rgb*(1. - Dd.g) +
texture2D(samp, vec2(tc1.r + h, tc1.g + h)).rgb*Dd.g)*Dd.r;
gl_FragColor = vec4( new, texture2D(samp, tc).a );
}
</script>
<script id="p-fs" type="x-shader/x-fragment">
precision highp float;
uniform sampler2D samp;
varying vec2 tc;
const float h = 1./512., h2 = 1./1024.;
void main(void) {
vec4 t = texture2D(samp, tc);
t.a =
(texture2D(samp, vec2(tc.r - h, tc.g)).a +
texture2D(samp, vec2(tc.r + h, tc.g)).a +
texture2D(samp, vec2(tc.r, tc.g - h)).a +
texture2D(samp, vec2(tc.r, tc.g + h)).a -
// (t.r - texture2D(samp, vec2(tc.r - h, tc.g)).r + is unstable !?
// t.g - texture2D(samp, vec2(tc.r, tc.g - h)).g) *h) *.25;
(texture2D(samp, vec2(tc.r + h, tc.g)).r -
texture2D(samp, vec2(tc.r - h, tc.g)).r +
texture2D(samp, vec2(tc.r, tc.g + h)).g -
texture2D(samp, vec2(tc.r, tc.g - h)).g) *h2) *.25;
gl_FragColor = t;
}
</script>
<script id="force-fs" type="x-shader/x-fragment">
precision highp float;
uniform sampler2D samp;
uniform float c;
varying vec2 tc;
const float h = 1./512.;
void main(void) {
vec4 t = texture2D(samp, tc);
t.g += c*(t.b + texture2D(samp, vec2(tc.r, tc.g + h)).b );
gl_FragColor = t;
}
</script>
<script id="div-fs" type="x-shader/x-fragment">
precision highp float;
uniform sampler2D samp;
varying vec2 tc;
const float n = 512., h = 1./n;
void main(void) {
vec4 t = texture2D(samp, tc);
t.r -= (texture2D(samp, vec2(tc.r + h, tc.g)).a - t.a)*n;
t.g -= (texture2D(samp, vec2(tc.r, tc.g + h)).a - t.a)*n;
gl_FragColor = t;
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec2 aPos;
attribute vec2 aTexCoord;
varying vec2 tc;
void main(void) {
gl_Position = vec4(aPos, 0., 1.);
tc = aTexCoord;
}
</script>
<script type="text/javascript">
function getShader ( gl, id ){
var shaderScript = document.getElementById ( id );
var str = "";
var k = shaderScript.firstChild;
while ( k ){
if ( k.nodeType == 3 ) str += k.textContent;
k = k.nextSibling;
}
var shader;
if ( shaderScript.type == "x-shader/x-fragment" )
shader = gl.createShader ( gl.FRAGMENT_SHADER );
else if ( shaderScript.type == "x-shader/x-vertex" )
shader = gl.createShader(gl.VERTEX_SHADER);
else return null;
gl.shaderSource(shader, str);
gl.compileShader(shader);
if (gl.getShaderParameter(shader, gl.COMPILE_STATUS) == 0)
alert(id + "\n" + gl.getShaderInfoLog(shader));
return shader;
}
var gl, prog_advec, prog_force, prog_p, prog_div, prog_show,
FBO, FBO1, texture, texture1,
timer, delay = 0, it = 10, frames = 0, time, animation,
n = 512, sampLoc;
function main() {
var c = document.getElementById("c");
var err = "Your browser does not support ";
if (!window.WebGLRenderingContext){
alert(err+"WebGL. See http://get.webgl.org");
return;}
try { gl = c.getContext("experimental-webgl");
} catch(e) {}
if ( !gl ) {alert("Can't get WebGL"); return;}
var ext;
try { ext = gl.getExtension("OES_texture_float");
} catch(e) {}
if ( !ext ) {alert(err + "OES_texture_float extension"); return;}
prog_force = gl.createProgram();
gl.attachShader(prog_force, getShader( gl, "shader-vs" ));
gl.attachShader(prog_force, getShader( gl, "force-fs" ));
gl.linkProgram(prog_force);
gl.useProgram(prog_force);
gl.uniform1f(gl.getUniformLocation(prog_force, "c"), .01*.5*10 );
prog_advec = gl.createProgram();
gl.attachShader(prog_advec, getShader( gl, "shader-vs" ));
gl.attachShader(prog_advec, getShader( gl, "advec-fs" ));
gl.linkProgram(prog_advec);
prog_p = gl.createProgram();
gl.attachShader(prog_p, getShader( gl, "shader-vs" ));
gl.attachShader(prog_p, getShader( gl, "p-fs" ));
gl.linkProgram(prog_p);
prog_div = gl.createProgram();
gl.attachShader(prog_div, getShader( gl, "shader-vs" ));
gl.attachShader(prog_div, getShader( gl, "div-fs" ));
gl.linkProgram(prog_div);
gl.useProgram(prog_div);
gl.uniform1i(gl.getUniformLocation(prog_div, "samp"), 1);
prog_show = gl.createProgram();
gl.attachShader(prog_show, getShader( gl, "shader-vs" ));
gl.attachShader(prog_show, getShader( gl, "shader-fs-show" ));
gl.linkProgram(prog_show);
gl.useProgram(prog_advec);
var aPosLoc = gl.getAttribLocation(prog_advec, "aPos");
var aTexLoc = gl.getAttribLocation(prog_advec, "aTexCoord");
gl.enableVertexAttribArray( aPosLoc );
gl.enableVertexAttribArray( aTexLoc );
var data = new Float32Array([-1,-1, 0,0, 1,-1, 1,0, -1,1, 0,1,
1,1, 1,1]);
gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
gl.vertexAttribPointer(aPosLoc, 2, gl.FLOAT, gl.FALSE, 16, 0);
gl.vertexAttribPointer(aTexLoc, 2, gl.FLOAT, gl.FALSE, 16, 8);
gl.uniform1i(gl.getUniformLocation(prog_advec, "samp"), 1);
var pixels = [], h = 2/n, T;
for(var i = 0; i<n; i++)
for(var j = 0; j<n; j++){
var x = h*(j-n/2), y = h*(i-n/2) - .75;
// if (x*x + y*y > .05) T = 0; else T= -3;
if (y > .05 | x > 0.05) T = 0; else T= -1;
pixels.push( T, T, T, 0 );
// pixels.push( 0, 0, T, 0 );
}
texture = gl.createTexture();
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, n, n, 0,
gl.RGBA, gl.FLOAT, new Float32Array(pixels));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
texture1 = gl.createTexture();
gl.activeTexture(gl.TEXTURE1);
gl.bindTexture(gl.TEXTURE_2D, texture1);
gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, n, n, 0,
gl.RGBA, gl.FLOAT, new Float32Array(pixels));
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
FBO = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0,
gl.TEXTURE_2D, texture, 0);
if( gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE)
alert(err + "FLOAT as the color attachment to an FBO");
FBO1 = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO1);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0,
gl.TEXTURE_2D, texture1, 0);
gl.useProgram(prog_p);
sampLoc = gl.getUniformLocation(prog_p, "samp");
timer = setInterval(fr, 500);
time = new Date().getTime();
animation = "animate";
// draw();
anim();
}
function draw(){
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO1);
gl.useProgram(prog_force);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO);
gl.useProgram(prog_advec);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
gl.useProgram(prog_p);
for(var i = 0; i < it; i++){
gl.uniform1i(sampLoc, 0);
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO1);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
gl.uniform1i(sampLoc, 1);
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
}
gl.uniform1i(sampLoc, 0);
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO1);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
gl.bindFramebuffer(gl.FRAMEBUFFER, FBO);
gl.useProgram(prog_div);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
gl.useProgram(prog_show);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
frames++;
}
function anim(){
draw();
switch ( animation ){
case "reset":
var pixels = [], T, h = 2/n;
for(var i = 0; i<n; i++)
for(var j = 0; j<n; j++){
var x = h*(j-n/2), y = h*(i-n/2) - .75;
if (x*x + y*y > .05) T = 0; else T= -2;
pixels.push( 0, 0, T, 0 );
}
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, n, n, 0,
gl.RGBA, gl.FLOAT, new Float32Array(pixels));
gl.bindTexture(gl.TEXTURE_2D, texture1);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, n, n, 0,
gl.RGBA, gl.FLOAT, new Float32Array(pixels));
animation = "animate";
case "animate":
if (delay == 0) requestAnimationFrame(anim);
else setTimeout("requestAnimationFrame(anim)", delay);
break;
case "stop":
break;
}
}
function run(v) {
if( animation == "animate" ){
animation = "stop";
document.getElementById('runBtn').value = "Run ";}
else{
animation = "animate";
document.getElementById('runBtn').value = "Stop";
anim();
}
}
function reset() {
if( animation == "stop" ){
animation = "reset";
document.getElementById('runBtn').value = "Stop";
anim();}
else animation = "reset";
}
function fr(){
var ti = new Date().getTime();
var fps = Math.round(1000*frames/(ti - time));
document.getElementById("framerate").value = fps;
frames = 0; time = ti;
}
function setDelay(val) {
delay = parseInt(val);
}
function setIt(val) {
it = parseInt(val);
}
function setBu(v) {
var bu = v.valueOf();
gl.useProgram(prog_force); // c = dt*b/2
gl.uniform1f(gl.getUniformLocation(prog_force, "c"), .001*.5*bu );
}
</script>
<style type="text/css">
H1{ font-size: 120%; color: green}
H2{ font-size: 100%; color: green}
pre{ color: rgb(196, 0, 0)}
</style>
</head>
<body onload="main()" data-gr-c-s-loaded="true">
<canvas id="c" width="512" height="512"></canvas>
<br><button onclick="reset()">Reset</button>
<input type="button" onclick="run()" value="Stop" size="1" id="runBtn">
β<input size="2" value="10" onchange="setBu( this.value )">
It<input size="1" value="10" onchange="setIt( this.value )">
delay<input size="1" value="0" onchange="setDelay( this.value )">
fps<input size="1" id="framerate">
<br>2d ink droplet in water dynamics. Set a new buoyancy value <i>β</i>.
This script makes <i>2 It</i> iterations every time step to calculate pressure.
Boundaries are periodic.
<p>NirViaje changed the color for Serena.</p>
<p>See <a href="https://www.ibiblio.org/e-notes/webgl/gpu/fluid.htm">2D fluid dynamics</a> for explanations.
</p><p><i>Yang Chenglin</i> sent my kindly this remark
<br>"I think when you advect something on staggered grid, different
velocities should be used for different values. The velocity used in
your code is just suitable for the density. To advect ux or uy,
different velocity is needed. This can explain why your droplet
simulation does not perform symmetrically enough (it flows right
slightly)."
</p><p><a href="http://math.ucr.edu/~karl/">Karl Fredrickson</a> made
more accurate <a href="https://www.ibiblio.org/e-notes/webgl/gpu/droplet16.htm">Droplet demo</a>.
</p><hr><a href="https://www.ibiblio.org/e-notes/webgl/gpu/contents.htm">Simulations on GPU</a>
<br><i>updated</i> 9 Aug 2012
</body></html>