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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Schwarzschild Black Hole</title>
<!-- using a couple functions from these guys
yes I'm a WebGL noob --!>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
<!--jQuery & Bootstrap --!>
<script src="http://code.jquery.com/jquery-1.11.2.min.js" type="text/javascript"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap-theme.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<!--WebGL Utils--!>
<script type="text/javascript" src="resources/webgl-utils.js"></script>
<!--Fullscreen query--!>
<script>
function fullscreen(){
var el = document.getElementById('canvas');
if(el.webkitRequestFullScreen) {
el.webkitRequestFullScreen();
}
else {
el.mozRequestFullScreen();
}
}
</script>
<!--The real magic--!>
<script>
var gl;
var neheTexture;
var bgTexture;
var haTexture;
var curtex;
var clicked = 0;
var clx;
var cly;
var orbiting = 1;
var regime = 1.0;
var targetvangle = 0.0;
document.addEventListener("DOMContentLoaded", initev, false);
function initev()
{
var canvas = document.getElementById("canvas");
canvas.addEventListener("mousedown", getPosition, false);
}
function getPosition(event)
{
var x = new Number();
var y = new Number();
var canvas = document.getElementById("canvas");
if (event.x != undefined && event.y != undefined)
{
x = event.x;
y = event.y;
}
else // Firefox method to get the position
{
x = event.clientX + document.body.scrollLeft +
document.documentElement.scrollLeft;
y = event.clientY + document.body.scrollTop +
document.documentElement.scrollTop;
}
x -= canvas.offsetLeft;
y -= canvas.offsetTop;
clicked = 1;
clx = x;
cly = y;
}
//functions called on settings form click events
function checkres(value)
{
var canvas = document.getElementById("canvas");
if (value == "240p")
{canvas.width=320;canvas.height=240;}
else if (value == "480p")
{canvas.width=640;canvas.height=480;}
else if (value == "786p")
{canvas.width=1024;canvas.height=786;}
else if (value =="1080p")
{canvas.width=1920;canvas.height=1080;}
}
function checktex(value)
{
if (value == "bg")
curtex = bgTexture;
else if (value == "ha")
curtex = haTexture;
else if (value == "lp")
curtex = lpTexture;
else if (value == "uv")
curtex = uvTexture;
else
curtex = Null;
}
function checkorb(value)
{
orbiting = value;
}
function checklook(value)
{
targetvangle = value;
}
// MAIN FUNCTION
window.onload = main;
function main() {
var canvas = document.getElementById("canvas");
gl = getWebGLContext(canvas);
if (!gl) {
return;
}
//Textures are loaded
initTexture();
//Shader compilation
vertexShader = createShaderFromScriptElement(gl, "2d-vertex-shader");
fragmentShader = createShaderFromScriptElement(gl, "2d-fragment-shader");
program = createProgram(gl, [vertexShader, fragmentShader]);
gl.useProgram(program);
//Uniform location
var positionLocation = gl.getAttribLocation(program, "a_position");
var timeUniform = gl.getUniformLocation(program, "time"); // Getting location
var rUniform = gl.getUniformLocation(program, "R"); // Getting location
var betaUniform = gl.getUniformLocation(program, "beta"); // Getting location
var gammaUniform = gl.getUniformLocation(program, "gamma"); // Getting location
var resUniform = gl.getUniformLocation(program, "resolution");
var lookUniform = gl.getUniformLocation(program, "viewrot");
//Radius/velocity display ID
var radiusP = document.getElementById("radiusP");
//Geometry (just a quad)
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
-1.0, -1.0,
1.0, -1.0,
-1.0, 1.0,
-1.0, 1.0,
1.0, -1.0,
1.0, 1.0]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
//The two uniform sampler location
var u_defLocation = gl.getUniformLocation(program, "defSampler"); //deflection lookup tex
var u_bgLocation = gl.getUniformLocation(program, "bgSampler"); //lat long sky sphere
//binding
gl.uniform1i(u_defLocation,2);
gl.uniform1i(u_bgLocation,3);
//start time
var timec = 3000*Math.random();
var R = 0.0;
var R_target;
var beta;
var gamma;
var lookangle = 0.0;
//canvas starts at high resolution and is only scaled down here, to fit screen
//this is done because things work weird otherwise
if (screen.width < 786){
canvas.width=640;
canvas.height=480;
}
else
{
canvas.width = 1024;
canvas.height = 786;
}
//MAIN LOOP
setInterval(function () {
if (clicked){
R_target = 1.55+8.35*cly/canvas.height;
R += 0.02 * (R_target - R);
}
else{
R = 7.0+2.9 * Math.sin(timec*0.0031);
}
regime += 0.01 * (orbiting - regime);
//relativity shit
var beta_orb = 0.707 * 1.0 / Math.sqrt(R-1.0);
var gamma_orb = 1. / Math.sqrt(1.0 - beta*beta);
beta = regime * beta_orb;
gamma = (1.-regime) + regime*gamma_orb;
//look angle
lookangle += 0.01 * (targetvangle - lookangle);
//updating info div
radiusP.innerHTML = "Distance: " + R.toFixed(2) + " S. radii<br>Orbital velocity: " + beta.toFixed(2) + " c<br>Orbital γ: "+gamma.toFixed(3)+"<br>";
if(orbiting)
if (R<=3.0)
radiusP.innerHTML += "<span class=\"label label-warning\">Unstable orbit</span><br><small>Inertial, but corrections needed.</small>";
else
radiusP.innerHTML += "<span class=\"label label-primary\">Stable orbit</span><br><small>Inertial, engines off</small>";
else
radiusP.innerHTML += "<span class=\"label label-danger\">Hovering</span><br><small>Accelerating, engines on.</small>";
//we must rebind textures every frame
gl.activeTexture(gl.TEXTURE2);
gl.bindTexture(gl.TEXTURE_2D, neheTexture);
gl.activeTexture(gl.TEXTURE3);
gl.bindTexture(gl.TEXTURE_2D, curtex);
// updating uniforms
gl.uniform1f(timeUniform, timec );
gl.uniform1f(rUniform, R);
gl.uniform1f(betaUniform, beta);
gl.uniform1f(gammaUniform, gamma);
gl.uniform2f(resUniform, canvas.width, canvas.height);
gl.uniform1f(lookUniform,lookangle);
// draw
gl.drawArrays(gl.TRIANGLES, 0, 6);
timec += regime;
},10);
}
function initTexture() {
neheTexture = gl.createTexture();
neheTexture.image = new Image();
neheTexture.image.onload = function() {
handleLoadedTexture(neheTexture)
}
neheTexture.image.src = "deflections_tex.png";
bgTexture = gl.createTexture();
bgTexture.image = new Image();
bgTexture.image.onload = function() {
handleLoadedTexture(bgTexture)
}
bgTexture.image.src = "tex/bg1024.png";
haTexture = gl.createTexture();
haTexture.image = new Image();
haTexture.image.onload = function() {
handleLoadedTexture(haTexture)
}
haTexture.image.src = "tex/ha1024.jpg";
lpTexture = gl.createTexture();
lpTexture.image = new Image();
lpTexture.image.onload = function() {
handleLoadedTexture(lpTexture)
}
lpTexture.image.src = "tex/lp1024.jpg";
uvTexture = gl.createTexture();
uvTexture.image = new Image();
uvTexture.image.onload = function() {
handleLoadedTexture(uvTexture)
}
uvTexture.image.src = "tex/uv1024.jpg";
curtex = bgTexture;
}
function handleLoadedTexture(texture) {
window.console.log("handleLoadedTexture " + texture.image.src);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.image);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.bindTexture(gl.TEXTURE_2D, null);
}
</script>
<!-- vertex shader -->
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec2 a_position;
void main() {
gl_Position = vec4(a_position, 0, 1);
}
</script>
<!-- fragment shader -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
//This shader is part magic, part luck
//so it stays uncommented for now
precision mediump float;
#define M_PI 3.1415926535897932384626433832795 //not enough digits
uniform sampler2D defSampler;
uniform sampler2D bgSampler;
uniform float time;
uniform vec2 resolution;
uniform float R;
uniform float beta;
uniform float gamma;
uniform float viewrot;
const float tanfov = 3.;
vec3 rotate(const vec3 v, float theta, const vec3 axis) {
float cosTheta = cos(theta);
return v * cosTheta + cross(axis, v) * sin(theta) + axis * dot(v, axis) * (1.0 - cosTheta);
}
vec4 stripes(vec3 view, float horizonflag) { //argument must be normalized
return vec4(horizonflag * step(fract(5.*atan(view.z,view.x)),.8) * step(fract(5.*acos(view.y)),.8) * vec3(1.,-view.y,view.y), 1.) ;
}
vec3 aberrate(vec3 original)
{
return vec3(-beta * length(original) + gamma * original.x, original.yz );
}
vec4 starfield(vec3 view, float horizonflag) {
float latitude = acos(view.y)/M_PI;
float longitude = atan(view.z,view.x)/(2.0*M_PI);
return min(
texture2D( bgSampler, vec2(longitude,latitude)),
vec4(horizonflag*vec3(1.,1.,1.),1.)
);
}
const float textureSize = 512.0;
const float texelSize = 1.0 / textureSize;
vec4 texture2DInterp( sampler2D textureSampler, vec2 uv ) //not actually used right now
{
vec4 tl = texture2D(textureSampler, uv);
vec4 tr = texture2D(textureSampler, uv + vec2(texelSize, 0));
vec4 bl = texture2D(textureSampler, uv + vec2(0, texelSize));
vec4 br = texture2D(textureSampler, uv + vec2(texelSize , texelSize));
vec2 f = fract( uv.xy * textureSize ); // get the decimal part
vec4 tA = mix( tl, tr, f.x ); // will interpolate the red dot in the image
vec4 tB = mix( bl, br, f.x ); // will interpolate the blue dot in the image
//return mix( tA, tB, f.y ); // will interpolate the green dot in the image
float st = smoothstep(0.,1.,f.y);
return tA*(1.0-st) + st*tB;
}
void main() {
//get screen coords
vec2 uvscr = gl_FragCoord.xy / resolution;
vec2 uv = (uvscr - 0.5) * vec2(1.,resolution.y/resolution.x);
uv *= tanfov;
vec3 uv3 = normalize( aberrate( rotate( vec3(uv, -1.0),viewrot,vec3(0,1,0) )));
float theta = acos(dot(uv3,vec3(0,0,-1)));
//float dphi = 2./(R*sin(theta));
//small-angle approximation
//float Phi_sa = M_PI - (theta - dphi);
vec2 params = vec2( (R-1.0)/9.0, 1. - theta /M_PI );
vec4 distcolor = texture2D(defSampler,params);
// VVV why we should have a .98 here will forever be a mistery
float Phi_ba = 2.* M_PI * (0.98*distcolor.r+0.1*(distcolor.g));
float Phi = Phi_ba; //(1.-step(theta,1.0))*Phi_sa + (step(theta,1.0))*Phi_ba;
vec3 v3 = -normalize(cross(vec3(0,0,-1),uv3));
uv3 = rotate(vec3(0,0,R), Phi, v3);
float nothorizon = max(
smoothstep(0.,0.05,texture2D(defSampler,params).r) * (1.-step(theta,0.01)) ,
(1.-step(theta,1.57))
);
uv3 = rotate(uv3, time * 0.0015, vec3(0., 1., 0.));
//vec4 color = textureCube(iChannel0, cubeTexCoord);
vec4 color = starfield(normalize(uv3), nothorizon);
gl_FragColor = color;
//gl_FragColor = texture2DInterp(bgSampler,(uv)*0.1); //DEBUG: test uv
//gl_FragColor = vec4(theta * vec3(1.,1.,1.),1.); //DEBUG: test theta
// gl_FragColor = vec4(Phi/(2.*M_PI) * vec3(1.,1.,1.),1.); //DEBUG: test Phi
}
</script>
</head>
<body >
<div class="container">
<div class="col-md-3 col-sm-3 col-xs-6">
<p>Click/tap on canvas to set distance.</p>
<p id="radiusP">Radius</p>
<h4>Look...</h4>
<form>
<input checked type="radio" name="lookradio" onclick="checklook(0.0)">Straight at the center<br>
<input type="radio" name="lookradio" onclick="checklook(-1.57)">Ahead in your orbit<br>
</form>
<h4><a href="../">
<span class="glyphicon glyphicon-question-sign" aria-hidden="true"></span> Explanation
</a></h4>
</div>
<div class="col-md-3 col-sm-3 col-xs-6">
<h4>Resolution</h4>
<form>
<input type="radio" name="resradio" onclick="checkres(this.value)" value="240p">320x240<br>
<input type="radio" name="resradio" onclick="checkres(this.value)" value="480p">640x480<br>
<input checked type="radio" name="resradio" onclick="checkres(this.value)" value="786p">1024x786<br>
<input type="radio" name="resradio" onclick="checkres(this.value)" value="1080p">1920x1080<br>
<br>
</form>
<button class="btn btn-default" onclick="fullscreen();"><span class="glyphicon glyphicon-fullscreen" aria-hidden="true"></span> Go Fullscreen</button>
<br>
</div>
<div class="col-md-3 col-sm-3 col-xs-6">
<h4>Texture</h4>
<form>
<input checked type="radio" name="texradio" onclick="checktex(this.value)" value="bg">Milky Way<br>
<input type="radio" name="texradio" onclick="checktex(this.value)" value="ha">H-alpha<br>
<input type="radio" name="texradio" onclick="checktex(this.value)" value="uv">lat-long grid<br>
<input type="radio" name="texradio" onclick="checktex(this.value)" value="lp">Image from from <a href="http://paulbourke.net/miscellaneous/littleplanet/">"Little Planet"</a><br>
<br>
</form>
</div>
<div class="col-md-3 col-sm-3 col-xs-6">
<h4>Orbit</h4>
<form>
<input checked type="radio" name="orbradio" onclick="checkorb(1)">Circular orbit<br>
<input type="radio" name="orbradio" onclick="checkorb(0)">Hover Schwarzschild-stationary<br>
</form>
</div>
</div>
<div height="30" style="display: inline-block;"></div>
<div class="row" width="1920">
<canvas id="canvas" width="1920" height="1080" style="margin-left: auto; margin-right: auto; display: block; padding: 0px;" ></canvas>
</div>
</body>
</html>