Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

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.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <canvas id="canvas" width="400" height="400"></canvas>
              
            
!

CSS

              
                
              
            
!

JS

              
                const VERTEX_SHADER = `#version 300 es
  // Below are 2 input attributes
  // The values for these attributes will be provided
  // by us in the javascript "world"

  // vec2 is a vector with 2 values representing the
  // vertex coordinates (x/y).
  in vec2 a_position;

  // vec3 is a vector with 3 values representing the
  // vertex color (r/g/b).
  in vec3 a_color;

  // output color for this vertex,
  // OpenGL will interpolate these values automatically
  out vec3 color;

  void main() {
    // convert coord from [0,1] space to [0,2] space
    vec2 zeroToTwo = a_position * 2.0;

    // convert coord from [0,2] space to [-1,1]
  	vec2 glCoordSpace = zeroToTwo - 1.0;

    // set the output in the global predefined gl_Position variable.
	  // Note a vertex has 4 values: x,y,z,w - we use 0,1 for z,w.
    gl_Position = vec4(glCoordSpace, 0, 1);

    // set the output color variable, just provide the user intput
    color = a_color;
  }
`;

const FRAG_SHADER = `#version 300 es
  precision highp float;

  // input color for this fragment, provided by OpenGL by
  // interpolating the output color variable that is in the
  // vertex shader.
  in vec3 color;

  // We should set this output param with the desired
  // fragment color
  out vec4 outColor;

  void main() {
    // just output the color we got, note we got vec3 (rgb)
	// and outColor is vec4, so we use 1.0 for the alpha.
    outColor = vec4(color, 1.0);
  }
`;

var canvas = document.getElementById('canvas');
// get webgl2 context
var gl = canvas.getContext('webgl2');

// Create shader object of type "VERTEX"
const vertexShader = gl.createShader(gl.VERTEX_SHADER);

// Load the shader source
gl.shaderSource(vertexShader, VERTEX_SHADER);

// Compile the shader
gl.compileShader(vertexShader);

// Check the compile status
var compiled = gl.getShaderParameter(vertexShader, gl.  COMPILE_STATUS);
if (!compiled) {
  // Something went wrong during compilation; get the error
  var lastError = gl.getShaderInfoLog(vertexShader);
  throw new Error('Error compiling shader:' + lastError);
}

// Do the same for the fragment shader
const fragShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragShader, FRAG_SHADER);
gl.compileShader(fragShader);

// Check the compile status
compiled = gl.getShaderParameter(fragShader, gl.  COMPILE_STATUS);
if (!compiled) {
  // Something went wrong during compilation; get the error
  var lastError = gl.getShaderInfoLog(fragShader);
  throw new Error('Error compiling shader:' + lastError);
}

// create program object
var program = gl.createProgram();

// attach it with the 2 shaders
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragShader);

// and link
gl.linkProgram(program);

// Check the link status
const linked = gl.getProgramParameter(program, gl.LINK_STATUS);
if (!linked) {
  // something went wrong with the link
  const lastError = gl.getProgramInfoLog(program);
  throw new Error('Error linking gl program:', lastError);
}

// First we create a "buffer", which is just a chunk of memory **on the GPU**:
var vertexParamsBuffer = gl.createBuffer();
// Then we should "bind" it, binding in OpenGL is like making something "active"
gl.bindBuffer(gl.ARRAY_BUFFER, vertexParamsBuffer);

var verticesData = new Float32Array([
  // coord      color
    0.0, 0.0,  1.0, 0.0, 0.0, // 1st vertex
    0.5, 1.0,  0.0, 1.0, 0.0, // 2nd vertex
    1.0, 0.0,  0.0, 0.0, 1.0  // 3ed vertex
]);

// First parameter is the "slot" onto which load the data
// Second parameter is the chunk of bytes
// Third parameter is a hint to OpenGL how this data used
gl.bufferData(gl.ARRAY_BUFFER, verticesData, gl.STATIC_DRAW);

// Gets the index of the a_position input attribute
var a_positionIdx = gl.getAttribLocation(program, 'a_position');

// Fact that we declared "in vec2 a_position" attribute
// in our vertex shader doesn't mean it is "active",
// we have to enable it specifically:
gl.enableVertexAttribArray(a_positionIdx);

// And now we tell OpenGL how to read data from the buffer
// CURRENTLY bound to the ARRAY_BUFFER "slot" into the
// vertex attribute a_position
gl.vertexAttribPointer(a_positionIdx, 2, gl.FLOAT, false, 20, 0);

// same for the color attribute
var a_colorIdx = gl.getAttribLocation(program, 'a_color');
gl.enableVertexAttribArray(a_colorIdx);
gl.vertexAttribPointer(a_colorIdx, 3, gl.FLOAT, false, 20, 8);

// First we set our program as the active program on the gpu
gl.useProgram(program);

// Call the draw method
gl.drawArrays(gl.TRIANGLES, 0, 3);

              
            
!
999px

Console