cssAudio - Activefile-genericCSS - ActiveGeneric - ActiveHTML - ActiveImage - ActiveJS - ActiveSVG - ActiveText - Activefile-genericVideo - ActiveLovehtmlicon-new-collectionicon-personicon-teamlog-outoctocatpop-outspinnerstartv

Pen Settings

CSS Base

Vendor Prefixing

Add External CSS

These stylesheets will be added in this order and before the code you write in the CSS editor. You can also add another Pen here, and it will pull the CSS from it. Try typing "font" or "ribbon" below.

Quick-add: + add another resource

Add External JavaScript

These scripts will run in this order and before the code in the JavaScript editor. You can also link to another Pen here, and it will run the JavaScript from it. Also try typing the name of any popular library.

Quick-add: + add another resource

Code Indentation

     

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

            
              /**
 * Part 4 Challenges:
 *
 * - Eliminate the if statement in the fragment shader using step() and mix()
 * - Make the motion of the metaball centers more complex by making
 *   them attracted to one another
 */

var canvas = document.getElementById("main");
var gl = canvas.getContext('webgl');

var NUM_METABALLS = 10;
var WIDTH = canvas.width;
var HEIGHT = canvas.height;

/**
 * Shaders
 */

// Utility to fail loudly on shader compilation failure
function compileShader(shaderSource, shaderType) {
    var shader = gl.createShader(shaderType);
    gl.shaderSource(shader, shaderSource);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        throw "Shader compile failed with: " + gl.getShaderInfoLog(shader);
    }

    return shader;
}

var vertexShader = compileShader('\n\
attribute vec2 position;\n\
\n\
void main() {\n\
    // position specifies only x and y.\n\
    // We set z to be 0.0, and w to be 1.0\n\
    gl_Position = vec4(position, 0.0, 1.0);\n\
}\
', gl.VERTEX_SHADER);

var fragmentShader = compileShader('\n\
precision highp float;\n\
uniform vec3 metaballs[' + NUM_METABALLS + '];\n\
const float WIDTH = ' + WIDTH + '.0;\n\
const float HEIGHT = ' + HEIGHT + '.0;\n\
\n\
void main(){\n\
    float x = gl_FragCoord.x;\n\
    float y = gl_FragCoord.y;\n\
    float v = 0.0;\n\
    for (int i = 0; i < ' + NUM_METABALLS + '; i++) {\n\
        vec3 mb = metaballs[i];\n\
        float dx = mb.x - x;\n\
        float dy = mb.y - y;\n\
        float r = mb.z;\n\
        v += r*r/(dx*dx + dy*dy);\n\
    }\n\
    if (v > 1.0) {\n\
        gl_FragColor = vec4(x/WIDTH, y/HEIGHT,\n\
                                0.0, 1.0);\n\
    } else {\n\
        gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);\n\
    }\n\
}\n\
', gl.FRAGMENT_SHADER);

var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
gl.useProgram(program);

/**
 * Geometry setup
 */

// Set up 4 vertices, which we'll draw as a rectangle
// via 2 triangles
//
//   A---C
//   |  /|
//   | / |
//   |/  |
//   B---D
//
// We order them like so, so that when we draw with
// gl.TRIANGLE_STRIP, we draw triangle ABC and BCD.
var vertexData = new Float32Array([
    -1.0,  1.0, // top left
    -1.0, -1.0, // bottom left
     1.0,  1.0, // top right
     1.0, -1.0, // bottom right
]);
var vertexDataBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexDataBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);

/**
 * Attribute setup
 */

// Utility to complain loudly if we fail to find the attribute

function getAttribLocation(program, name) {
    var attributeLocation = gl.getAttribLocation(program, name);
    if (attributeLocation === -1) {
        throw 'Can not find attribute ' + name + '.';
    }
    return attributeLocation;
}

// To make the geometry information available in the shader as attributes, we
// need to tell WebGL what the layout of our data in the vertex buffer is.
var positionHandle = getAttribLocation(program, 'position');
gl.enableVertexAttribArray(positionHandle);
gl.vertexAttribPointer(positionHandle,
                       2, // position is a vec2
                       gl.FLOAT, // each component is a float
                       gl.FALSE, // don't normalize values
                       2 * 4, // two 4 byte float components per vertex
                       0 // offset into each span of vertex data
                       );

/**
 * Simulation setup
 */

var metaballs = [];

for (var i = 0; i < NUM_METABALLS; i++) {
  var radius = Math.random() * 60 + 10;
  metaballs.push({
    x: Math.random() * (WIDTH - 2 * radius) + radius,
    y: Math.random() * (HEIGHT - 2 * radius) + radius,
    vx: Math.random() * 10 - 5,
    vy: Math.random() * 10 - 5,
    r: radius
  });
}

/**
 * Uniform setup
 */

// Utility to complain loudly if we fail to find the uniform
function getUniformLocation(program, name) {
    var uniformLocation = gl.getUniformLocation(program, name);
    if (uniformLocation === -1) {
        throw 'Can not find uniform ' + name + '.';
    }
    return uniformLocation;
}
var metaballsHandle = getUniformLocation(program, 'metaballs');

/**
 * Simulation step, data transfer, and drawing
 */

var step = function() {
  // Update positions and speeds
  for (var i = 0; i < NUM_METABALLS; i++) {
    var mb = metaballs[i];
    
    mb.x += mb.vx;
    if (mb.x - mb.r < 0) {
      mb.x = mb.r + 1;
      mb.vx = Math.abs(mb.vx);
    } else if (mb.x + mb.r > WIDTH) {
      mb.x = WIDTH - mb.r;
      mb.vx = -Math.abs(mb.vx);
    }
    mb.y += mb.vy;
    if (mb.y - mb.r < 0) {
      mb.y = mb.r + 1;
      mb.vy = Math.abs(mb.vy);
    } else if (mb.y + mb.r > HEIGHT) {
      mb.y = HEIGHT - mb.r;
      mb.vy = -Math.abs(mb.vy);
    }
  }
  
  // To send the data to the GPU, we first need to
  // flatten our data into a single array.
  var dataToSendToGPU = new Float32Array(3 * NUM_METABALLS);
  for (var i = 0; i < NUM_METABALLS; i++) {
    var baseIndex = 3 * i;
    var mb = metaballs[i];
    dataToSendToGPU[baseIndex + 0] = mb.x;
    dataToSendToGPU[baseIndex + 1] = mb.y;
    dataToSendToGPU[baseIndex + 2] = mb.r;
  }
  gl.uniform3fv(metaballsHandle, dataToSendToGPU);

  gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

  requestAnimationFrame(step);
};

step();


            
          
!
999px
Loading ..................

Console