如何在javascript中包含液体？

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

var canvas = document.getElementById('liquidCanvas');
var ctx = canvas.getContext('2d');

var gl = canvas.getContext('webgl');

// 顶点着色器
var vertexShaderSource = `
    attribute vec2 a_position;
    void main() {
        gl_Position = vec4(a_position, 0, 1);
    }
`;

// 片段着色器
var fragmentShaderSource = `
    precision mediump float;
    void main() {
        gl_FragColor = vec4(0, 0, 1, 1); // 设置颜色为蓝色
    }
`;

// 创建顶点着色器
var vertexShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertexShader, vertexShaderSource);
gl.compileShader(vertexShader);

// 创建片段着色器
var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragmentShader, fragmentShaderSource);
gl.compileShader(fragmentShader);

// 创建着色器程序
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
gl.useProgram(program);

// 创建缓冲区
var positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

// 定义顶点数据
var positions = [
    -1, -1,
    1, -1,
    -1, 1,
    1, 1
];

// 将顶点数据存入缓冲区
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);

// 获取顶点着色器中的属性位置
var positionAttributeLocation = gl.getAttribLocation(program, 'a_position');

// 启用属性数组
gl.enableVertexAttribArray(positionAttributeLocation);

// 告诉WebGL如何从缓冲区中读取顶点数据
gl.vertexAttribPointer(positionAttributeLocation, 2, gl.FLOAT, false, 0, 0);

// 清空画布
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);

// 绘制液体
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);