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How To Manage Data in WebGL?

Last Updated : 05 Sep, 2024
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WebGL (Web Graphics Library) is a JavaScript API that allows you to create 3D graphics that run in any web browser without needing plugins. It's a powerful tool for rendering interactive 3D and 2D graphics, utilizing the capabilities of the GPU.

To effectively create and manipulate these graphics, managing data in WebGL is very important. It involves understanding how to work with buffers, shaders, and data types like vertices, colors, and indices.

WebGL Data Types

In WebGL, data is primarily used to define the geometry of 3D objects, their colors, textures, and how they should be rendered some of them are:

  • Vertices: Points in 3D space that define the shape of an object.
  • Colors: Values that define the color of each vertex or the entire object.
  • Indices: Numbers that tell WebGL how to connect vertices to form shapes like triangles.
  • Textures: Images or patterns that are mapped onto the surfaces of 3D objects to give them a more realistic appearance.

Approach To Manage Data in WebGL

Managing data in WebGL involves:

  • Creating and binding buffers to store data.
  • Writing shaders to process this data.
  • Rendering objects on the canvas using WebGL commands. It enables dynamic and interactive graphics in web browsers.

Step 1:Setting Up WebGL

Before we can manage data in WebGL, we need to set up a WebGL context in our HTML file.

HTML 
< !DOCTYPE html >
    <html>
        <head>
            <title>WebGL Example</title>
        </head>
        <body>
            <canvas id="glCanvas" width="640" height="480"></canvas>
            <script>
      // Get the canvas element
                var canvas = document.getElementById("glCanvas");

                // Initialize WebGL context
                var gl = canvas.getContext("webgl");

                if (!gl) {
                    console.error("WebGL not supported, falling back on experimental-webgl");
                gl = canvas.getContext("experimental-webgl");
      }

                if (!gl) {
                    alert("Your browser does not support WebGL");
      }
            </script>
        </body>
    </html>

Step 2: Creating Buffers for Data

In WebGL, a buffer is a place in memory where data is stored. We create buffers to store data such as vertex positions, colors, and indices.

Vertex Buffer : Stores the position of each vertex.

JavaScript 
// Create a buffer for the vertex positions
var vertexBuffer = gl.createBuffer();

// Bind the buffer so we can write to it
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

// Define the positions of the vertices of a triangle
var vertices = new Float32Array([
    0.0, 1.0, 0.0,
    -1.0, -1.0, 0.0,
    1.0, -1.0, 0.0
]);

// Send the vertex data to the buffer
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);


Color Buffer: Stores the color of each vertex. This can be done similarly by creating a color buffer and storing colors as an array of values.

JavaScript 
// Create a buffer for the vertex colors
var colorBuffer = gl.createBuffer();

// Bind the buffer so we can write to it
gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);

// Define colors for the vertices
var colors = new Float32Array([
    1.0, 0.0, 0.0, 1.0,  // Red
    0.0, 1.0, 0.0, 1.0,  // Green
    0.0, 0.0, 1.0, 1.0   // Blue
]);

// Send the color data to the buffer
gl.bufferData(gl.ARRAY_BUFFER, colors, gl.STATIC_DRAW);


Index Buffer: Used to define how vertices should be connected to form triangles.

JavaScript 
// Create a buffer for the vertex indices
var indexBuffer = gl.createBuffer();

// Bind the buffer so we can write to it
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);

// Define the indices
var indices = new Uint16Array([0, 1, 2]);

// Send the index data to the buffer
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

Step 3: Creating and Compiling Shaders

Shaders are small programs that run on the GPU and tell WebGL how to draw the vertices. We need two shaders: a vertex shader and a fragment shader.

Vertex Shader: Processes each vertex and determines its position on the screen.

JavaScript 
var vertexShaderSource = `
    attribute vec3 coordinates;
    attribute vec4 color;
    varying vec4 vColor;
    void main(void) {
        gl_Position = vec4(coordinates, 1.0);
        vColor = color;
  }
`;

var vertexShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertexShader, vertexShaderSource);
gl.compileShader(vertexShader);


Fragment Shader: Determines the color of each pixel.

JavaScript 
var fragmentShaderSource = `
    precision mediump float;
    varying vec4 vColor;
    void main(void) {
        gl_FragColor = vColor;
  }
`;

var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragmentShader, fragmentShaderSource);
gl.compileShader(fragmentShader);

Step 4: Linking Shaders and Using Programs

Once shaders are compiled, we link them into a program that WebGL can use to render our objects.

JavaScript 
// Create a WebGL program and attach the shaders
var shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);

// Bind the vertex buffer to the shader program
var coord = gl.getAttribLocation(shaderProgram, "coordinates");
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.vertexAttribPointer(coord, 3, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(coord);

// Bind the color buffer to the shader program
var color = gl.getAttribLocation(shaderProgram, "color");
gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
gl.vertexAttribPointer(color, 4, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(color);

Step 5: Drawing the Scene

Finally, we draw our scene. We clear the canvas and then draw the object using the data in our buffers.

JavaScript 
// Clear the canvas
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);

// Draw the triangle
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT, 0);

Compile the code together:

HTML 
<!DOCTYPE html>
<html>

<head>
    <title>WebGL Example</title>
</head>

<body>
    <canvas id="glCanvas" width="640" height="480"></canvas>
    <script>
        // Get the canvas element
        var canvas = document.getElementById("glCanvas");

        // Initialize WebGL context
        var gl = canvas.getContext("webgl");

        if (!gl) {
            console.error("WebGL not supported, falling back on experimental-webgl");
            gl = canvas.getContext("experimental-webgl");
        }

        if (!gl) {
            alert("Your browser does not support WebGL");
        }

        // Define the vertex positions
        var vertices = new Float32Array([
            0.0, 1.0, 0.0,
            -1.0, -1.0, 0.0,
            1.0, -1.0, 0.0
        ]);

        // Create a buffer for the vertex positions
        var vertexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

        // Define the colors for each vertex
        var colors = new Float32Array([
            1.0, 0.0, 0.0, 1.0,  // Red
            0.0, 1.0, 0.0, 1.0,  // Green
            0.0, 0.0, 1.0, 1.0   // Blue
        ]);

        // Create a buffer for the vertex colors
        var colorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, colors, gl.STATIC_DRAW);

        // Define the indices for the triangle
        var indices = new Uint16Array([0, 1, 2]);

        // Create a buffer for the indices
        var indexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER,
            indexBuffer);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
            indices, gl.STATIC_DRAW);

        // Vertex shader program
        var vertexShaderSource = `
        attribute vec3 coordinates;
        attribute vec4 color;
        varying vec4 vColor;
        void main(void) {
          gl_Position = vec4(coordinates, 1.0);
          vColor = color;
        }
      `;
        var vertexShader = gl.createShader(gl.VERTEX_SHADER);
        gl.shaderSource(vertexShader,
            vertexShaderSource);
        gl.compileShader(vertexShader);

        // Fragment shader program
        var fragmentShaderSource = `
        precision mediump float;
        varying vec4 vColor;
        void main(void) {
          gl_FragColor = vColor;
        }
      `;
        var fragmentShader = gl.createShader(gl
            .FRAGMENT_SHADER);
        gl.shaderSource(fragmentShader,
            fragmentShaderSource);
        gl.compileShader(fragmentShader);

        // Create and use the WebGL program
        var shaderProgram = gl.createProgram();
        gl.attachShader(shaderProgram,
            vertexShader);
        gl.attachShader(shaderProgram,
            fragmentShader);
        gl.linkProgram(shaderProgram);
        gl.useProgram(shaderProgram);

        // Bind the vertex buffer to the shader program
        var coord = gl.getAttribLocation(shaderProgram, "coordinates");
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
        gl.vertexAttribPointer(coord, 3, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray(coord);

        // Bind the color buffer to the shader program
        var color = gl.getAttribLocation(shaderProgram, "color");
        gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
        gl.vertexAttribPointer(color, 4, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray(color);

        // Clear the canvas
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);

        // Draw the triangle
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
        gl.drawElements(gl.TRIANGLES,
            indices.length, gl.UNSIGNED_SHORT, 0);
    </script>
</body>

</html>


Output:

Screenshot-2024-08-31-082514
How to Manage Data in WebGL

Next Article
How To Compile Shaders In WebGL?

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