shaku/src/gfx/mesh_generator.js

A simple and effective JavaScript game development framework that knows its place!

/**
 * Define utility to generate meshes.
 * 
 * |-- copyright and license --|
 * @module     Shaku
 * @file       shaku\src\gfx\mesh_generator.js
 * @author     Ronen Ness (ronenness@gmail.com | http://ronenness.com)
 * @copyright  (c) 2021 Ronen Ness
 * @license    MIT
 * |-- end copyright and license --|
 * 
 */

'use strict';

const Mesh = require("./mesh");

/**
 * Utility class to generate meshes.
 * @private
 */
class MeshGenerator
{
    /**
     * Create the mesh generator.
     */
    constructor(gl)
    {
        this._gl = gl;
    }

    /**
     * Generate and return a textured quad.
     * @returns {Mesh} Quad mesh.
     */
    quad()
    {
        const gl = this._gl;

        const positionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
        let x = 0.5; // <- 0.5 so total size would be 1x1
        const positions = [
            -x, -x,  0,
             x, -x,  0,
            -x,  x,  0,
            x,  x,  0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
    
        const textureCoordBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, textureCoordBuffer);
        const textureCoordinates = [
            0.0,  0.0,
            1.0,  0.0,
            0.0,  1.0,
            1.0,  1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates), gl.STATIC_DRAW);

        const colorsBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, colorsBuffer);
        const colors = [
            1,1,1,1,
            1,1,1,1,
            1,1,1,1,
            1,1,1,1,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.DYNAMIC_DRAW);
    
        const indexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
        const indices = [
            0, 1, 3, 2
        ];
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);
    
        return new Mesh(positionBuffer, textureCoordBuffer, colorsBuffer, indexBuffer, indices.length);
    }
}

// export the meshes generator.
module.exports = MeshGenerator;