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// # Rendering Signed Distance Functions with WebGL
//
// Yes, you can do this in Shadertoy, but this is how you can do it from scratch.
// (It also loads a lot faster.)
//
// Use it by opening the Scratchpad in Firefox and evaluate the code with `Ctrl-R`
// to rerender. Including via `<script>` should also work.
//
// # Resources
//
// - [Raw WebGL](http://nickdesaulniers.github.io/RawWebGL) ([video](https://www.youtube.com/watch?v=H4c8t6myAWU))
// - [WebGL Fundamentals](http://webglfundamentals.org/webgl/lessons/webgl-fundamentals.html)
try {
document.body.style = "margin: 0; overflow: hidden;";
document.body.innerHTML = "";
var errorEl = document.createElement("pre");
errorEl.style = "color: red; position: absolute; right: 0; bottom: 0;";
document.body.appendChild(errorEl);
function displayError(e) {
window.error = e;
errorEl.textContent = e;
console.error(e);
}
function clearError() {
errorEl.textContent = "";
}
function compileShader(gl, type, shaderSrc) {
var shader = gl.createShader(type);
gl.shaderSource(shader, shaderSrc);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
throw new Error(gl.getShaderInfoLog(shader));
}
return shader;
}
function linkShaders(gl, vertexShader, fragmentShader) {
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
throw new Error(gl.getProgramInfoLog(program));
}
return program;
}
function initBuffer(gl, data, elemPerVertex, attribute) {
var buffer = gl.createBuffer();
if (!buffer) {
throw new Error('failed to create buffer');
}
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
gl.vertexAttribPointer(attribute, elemPerVertex, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(attribute);
}
var vertexShaderSrc = `
attribute vec4 aPosition;
void main() {
gl_Position = aPosition;
}
`
var fragmentShaderSrc = `
precision highp float;
uniform vec2 iResolution;
uniform vec3 iMouse;
const int MaximumRaySteps = 150;
const float MinimumDistance = 0.0000001;
float DistanceEstimator(vec3 pos);
float trace(vec3 from, vec3 direction) {
float totalDistance = 0.0;
int stepsDone = 0;
for (int steps = 0; steps < MaximumRaySteps; steps++) {
vec3 p = from + totalDistance * direction;
float distance = DistanceEstimator(p);
totalDistance += distance;
stepsDone = steps;
if (distance < MinimumDistance) break;
}
return 1.0-float(stepsDone)/float(MaximumRaySteps);
}
float DistanceEstimator(vec3 pos) {
return length(pos) - 1.0;
}
/*uniform int MaxIterations; //#slider[1,50,200]
const float bailout = 4.0;
const float power = 8.0;
const float phaseX = 0.0;
const float phaseY = 0.0;
float DistanceEstimator(vec3 z0) {
vec3 c = z0;
vec3 z = z0;
float pd = power - 1.0; // power for derivative
// Convert z to polar coordinates
float r = length(z);
float th = atan(z.y, z.x);
float ph = asin(z.z / r);
vec3 dz;
float ph_dz = 0.0;
float th_dz = 0.0;
float r_dz = 1.0;
float powR, powRsin;
// Iterate to compute the distance estimator.
for (int n = 0; n < MaxIterations; n++) {
// Calculate derivative of
powR = power * pow(r, pd);
powRsin = powR * r_dz * sin(ph_dz + pd*ph);
dz.x = powRsin * cos(th_dz + pd*th) + 1.0;
dz.y = powRsin * sin(th_dz + pd*th);
dz.z = powR * r_dz * cos(ph_dz + pd*ph);
// polar coordinates of derivative dz
r_dz = length(dz);
th_dz = atan(dz.y, dz.x);
ph_dz = acos(dz.z / r_dz);
// z iteration
powR = pow(r, power);
powRsin = sin(power*ph);
z.x = powR * powRsin * cos(power*th);
z.y = powR * powRsin * sin(power*th);
z.z = powR * cos(power*ph);
z += c;
r = length(z);
if (r > bailout) break;
th = atan(z.y, z.x) + phaseX;
ph = acos(z.z / r) + phaseY;
}
// Return the distance estimation value which determines the next raytracing
// step size, or if whether we are within the threshold of the surface.
return 0.5 * r * log(r)/r_dz;
}*/
mat3 setCamera( in vec3 ro, in vec3 ta, float cr ) {
vec3 cw = normalize(ta-ro);
vec3 cp = vec3(sin(cr), cos(cr),0.0);
vec3 cu = normalize( cross(cw,cp) );
vec3 cv = normalize( cross(cu,cw) );
return mat3( cu, cv, cw );
}
uniform vec3 origin; //#slider[(-10.0,1.0,10.0),(-10.0,2.0,10.0),(-10.0,-1.0,10.0)]
uniform vec3 angle; //#slider[(-3.0,0.0,3.0),(-3.0,0.0,3.0),(-3.0,0.0,3.0)]
uniform vec3 color; //#slider[(0.0, 1.0, 1.0),(0.0,0.0,1.0),(0.0,0.0,1.0)]
uniform float colorMix; //#slider[0.0,0.9,1.0]
void main() {
vec2 q = gl_FragCoord.xy / iResolution.xy;
vec2 p = -1.0 + 2.0*q;
p.x *= iResolution.x / iResolution.y;
vec2 mo = iMouse.xy/iResolution.xy;
float time = 15.0 + 0.0; // iGlobalTime
// camera
vec3 ro = origin; //vec3( -0.5+3.2*cos(0.1*time + 6.0*mo.x), 1.0 + 2.0*mo.y, 0.5 + 3.2*sin(0.1*time + 6.0*mo.x) );
vec3 ta = angle; //vec3( -0.5, -0.4, 0.5 );
// camera-to-world transformation
mat3 ca = setCamera( ro, ta, 0.0 );
// ray direction
vec3 rd = ca * normalize( vec3(p.xy, 2.5) );
// render
float dist = trace(ro, rd);
vec3 col = vec3(dist, dist, dist);
col = mix(color, col, colorMix);
//col = pow( col, vec3(0.4545));
gl_FragColor = vec4( col, 1.0 );
}
`
var styleEl = document.createElement("style");
styleEl.textContent = `
#sidebar {
position: absolute;
top: 0;
right: -250px;
z-index: 1;
padding: 1ex;
font-family: monospace;
font-weight: bold;
background-color: rgba(255, 255, 255, 0.5);
}
#sidebar:hover {
transition: right 0.1s;
right: 0;
}
#editor {
position: absolute;
top: 0;
left: 0;
border: none;
background-color: rgba(255, 255, 255, 0.5);
min-width: 72ex;
height: 100vh;
}
`
document.head.appendChild(styleEl);
function TwoTriangles(canvas, fragmentShaderSrc) {
var tt = {};
tt.canvas = canvas;
tt.fragmentShaderSrc = fragmentShaderSrc;
tt.w = canvas.width = window.innerWidth;
tt.h = canvas.height = window.innerHeight;
var gl = tt.gl = canvas.getContext("webgl");
if (!gl) { alert("i think your browser does not support webgl"); }
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
var vertexShader = compileShader(gl, gl.VERTEX_SHADER, vertexShaderSrc);
var fragmentShader = compileShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSrc);
var program = tt.program = linkShaders(gl, vertexShader, fragmentShader);
gl.useProgram(program);
var aPosition = gl.getAttribLocation(program, 'aPosition');
var iResolution = gl.getUniformLocation(program, 'iResolution');
var iGlobalTime = gl.getUniformLocation(program, 'iGlobalTime');
var iMouse = gl.getUniformLocation(program, 'iMouse');
gl.vertexAttrib2f(aPosition, 0.0, 0.0);
gl.uniform2f(iResolution, canvas.width, canvas.height);
gl.uniform1f(iGlobalTime, 0.0);
gl.uniform3f(iMouse, 0.0, 0.0, 0.0);
// two triangles
var positions = 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
]);
initBuffer(gl, positions, 2, aPosition);
tt.render = function() {
gl.drawArrays(gl.TRIANGLES, 0, 6);
};
tt.draw = function() {
requestAnimationFrame(draw);
render();
}
tt.canvas.addEventListener("mousemove", function(ev) {
gl.uniform3f(iMouse, ev.mouseX, ev.mouseY, 0.0);
});
window.onresize = function(ev) {
tt.w = tt.canvas.width = window.innerWidth;
tt.h = tt.canvas.height = window.innerHeight;
gl.viewport(0, 0, tt.w, tt.h);
gl.uniform2f(iResolution, tt.w, tt.h);
tt.render();
};
tt.render();
return tt;
}
var canvas = document.createElement("canvas");
document.body.appendChild(canvas);
var tt = TwoTriangles(canvas, fragmentShaderSrc);
var sidebarEl = document.createElement("div");
sidebarEl.id = "sidebar";
document.body.appendChild(sidebarEl);
var sliders = findSliders(fragmentShaderSrc);
initSliders(tt.gl, tt.program, sliders, function(ev) {
requestAnimationFrame(tt.render);
});
addSliders(sidebarEl, sliders);
tt.render();
var editor = {};
editor.visible = true;
editor.el = document.createElement("textarea");
editor.el.id = "editor";
editor.el.value = tt.fragmentShaderSrc;
document.body.appendChild(editor.el);
editor.el.onkeydown = function(ev) {
try {
if (ev.ctrlKey && ev.keyCode == 13) {
tt = TwoTriangles(canvas, editor.el.value);
sidebarEl.innerHTML = "";
sliders = findSliders(tt.fragmentShaderSrc);
initSliders(tt.gl, tt.program, sliders, function(ev) {
requestAnimationFrame(tt.render);
});
addSliders(sidebarEl, sliders);
tt.render();
clearError();
}
} catch (e) {
displayError(e);
}
}
editor.toggle = function() {
if (editor.visible) {
editor.el.style.display = "none";
} else {
editor.el.style.display = "inherit";
editor.el.focus();
}
editor.visible = !editor.visible;
}
window.addEventListener('keydown', function(ev) {
if (ev.ctrlKey && ev.keyCode == 72) {
ev.preventDefault();
editor.toggle();
}
})
} catch (e) {
displayError(e);
}
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