#yyds干货盘点#愚公系列2022年12月 微信小程序-WebGL画渐变色正方形
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前言
在现实中webgl的用途很多,比如医院运维网站,地铁运维网站,海绵城市,可以以三维网页形式展示出现实状态。
WebGL相关文档:http://doc.yonyoucloud.com/doc/wiki/project/webgl/webgL-fundamentals.html
一、webgl的使用
安装第三方包:npm i --save threejs-miniprogram
1.画正方形
import drawRectangle from ./draw-rectangle
Page(
/**
* 页面的初始数据
*/
data:
,
/**
* 生命周期函数--监听页面加载
*/
onLoad: function (options)
,
/**
* 生命周期函数--监听页面初次渲染完成
*/
onReady: function ()
wx.createSelectorQuery()
.select(#myCanvas1)
.node()
.exec((res) =>
const canvas = res[0].node
const gl = canvas.getContext(webgl)
if (!gl)
console.log(webgl未受支持);
return
// 检查所有支持的扩展
var available_extensions = gl.getSupportedExtensions();
console.log(available_extensions);
// 清除画布
// 使用完全不透明的黑色清除所有图像,我们将清除色设为黑色,此时并没有开始清除
gl.clearColor(0.0, 0.0, 0.0, 1.0);
// 用上面指定的颜色清除缓冲区
gl.clear(gl.COLOR_BUFFER_BIT);
// 画的是一个正方形
drawRectangle(gl)
)
import
mat4
from ../../lib/gl-matrix
function drawColorRectangle(gl)
// Vertex shader program
const vsSource = `
attribute vec4 aVertexPosition;
attribute vec4 aVertexColor;
uniform mat4 uModelViewMatrix;
uniform mat4 uProjectionMatrix;
varying lowp vec4 vColor;
void main(void)
gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;
vColor = aVertexColor;
`;
// Fragment shader program
// 每个片段只是根据其相对于顶点的位置得到一个插值过的颜色,而不是一个指定的颜色值。
// lowp表示低精度
// lowp, mediump和highp
const fsSource = `
varying lowp vec4 vColor;
void main(void)
gl_FragColor = vColor;
`;
// Initialize a shader program; this is where all the lighting
// for the vertices and so forth is established.
const shaderProgram = initShaderProgram(gl, vsSource, fsSource);
// Collect all the info needed to use the shader program.
// Look up which attributes our shader program is using
// for aVertexPosition, aVevrtexColor and also
// look up uniform locations.
const programInfo =
program: shaderProgram,
attribLocations:
vertexPosition: gl.getAttribLocation(shaderProgram, aVertexPosition),
vertexColor: gl.getAttribLocation(shaderProgram, aVertexColor),
,
uniformLocations:
projectionMatrix: gl.getUniformLocation(shaderProgram, uProjectionMatrix),
modelViewMatrix: gl.getUniformLocation(shaderProgram, uModelViewMatrix),
,
;
// Heres where we call the routine that builds all the
// objects well be drawing.
const buffers = initBuffers(gl);
// Draw the scene
drawScene(gl, programInfo, buffers);
//
// initBuffers
//
// Initialize the buffers well need. For this demo, we just
// have one object -- a simple two-dimensional square.
//
function initBuffers(gl)
// Create a buffer for the squares positions.
const positionBuffer = gl.createBuffer();
// Select the positionBuffer as the one to apply buffer
// operations to from here out.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Now create an array of positions for the square.
const positions = [
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, -1.0, 0.0
];
// Now pass the list of positions into WebGL to build the
// shape. We do this by creating a Float32Array from the
// javascript array, then use it to fill the current buffer.
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
// Now set up the colors for the vertices
// 此数组中包含四组四值向量,每一组向量代表一个顶点的颜色。
var colors = [
1.0, 1.0, 1.0, 1.0, // white
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
];
const colorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
return
position: positionBuffer,
color: colorBuffer,
;
//
// Draw the scene.
//
function drawScene(gl, programInfo, buffers)
gl.clearColor(0.0, 0.0, 0.0, 1.0); // Clear to black, fully opaque
gl.clearDepth(1.0); // Clear everything
gl.enable(gl.DEPTH_TEST); // Enable depth testing
gl.depthFunc(gl.LEQUAL); // Near things obscure far things
// Clear the canvas before we start drawing on it.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Create a perspective matrix, a special matrix that is
// used to simulate the distortion of perspective in a camera.
// Our field of view is 45 degrees, with a width/height
// ratio that matches the display size of the canvas
// and we only want to see objects between 0.1 units
// and 100 units away from the camera.
const fieldOfView = 45 * Math.PI / 180; // in radians
const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
const zNear = 0.1;
const zFar = 100.0;
const projectionMatrix = mat4.create();
// note: glmatrix.js always has the first argument
// as the destination to receive the result.
mat4.perspective(projectionMatrix,
fieldOfView,
aspect,
zNear,
zFar);
// Set the drawing position to the "identity" point, which is
// the center of the scene.
const modelViewMatrix = mat4.create();
// Now move the drawing position a bit to where we want to
// start drawing the square.
mat4.translate(modelViewMatrix, // destination matrix
modelViewMatrix, // matrix to translate
[-0.0, 0.0, -6.0]); // amount to translate
// Tell WebGL how to pull out the positions from the position
// buffer into the vertexPosition attribute
const numComponents = 3;
const type = gl.FLOAT;
const normalize = false;
const stride = 0;
const offset = 0;
gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
gl.vertexAttribPointer(
programInfo.attribLocations.vertexPosition,
numComponents,
type,
normalize,
stride,
offset);
gl.enableVertexAttribArray(
programInfo.attribLocations.vertexPosition);
// Tell WebGL how to pull out the colors from the color buffer
// into the vertexColor attribute.
const numComponents = 4;
const type = gl.FLOAT;
const normalize = false;
const stride = 0;
const offset = 0;
gl.bindBuffer(gl.ARRAY_BUFFER, buffers.color);
gl.vertexAttribPointer(
programInfo.attribLocations.vertexColor,
numComponents,
type,
normalize,
stride,
offset);
gl.enableVertexAttribArray(
programInfo.attribLocations.vertexColor);
// Tell WebGL to use our program when drawing
gl.useProgram(programInfo.program);
// Set the shader uniforms
gl.uniformMatrix4fv(
programInfo.uniformLocations.projectionMatrix,
false,
projectionMatrix);
gl.uniformMatrix4fv(
programInfo.uniformLocations.modelViewMatrix,
false,
modelViewMatrix);
const offset = 0;
const vertexCount = 4;
gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
//
// Initialize a shader program, so WebGL knows how to draw our data
//
function initShaderProgram(gl, vsSource, fsSource)
const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
// Create the shader program
const shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
// If creating the shader program failed, alert
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS))
alert(Unable to initialize the shader program: + gl.getProgramInfoLog(shaderProgram));
return null;
return shaderProgram;
//
// creates a shader of the given type, uploads the source and
// compiles it.
//
function loadShader(gl, type, source)
const shader = gl.createShader(type);
// Send the source to the shader object
gl.shaderSource(shader, source);
// Compile the shader program
gl.compileShader(shader);
// See if it compiled successfully
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
alert(An error occurred compiling the shaders: + gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
return null;
return shader;
export default drawColorRectangle
实际效果
二、相关包源码
gl-matrix相关包源码链接如下: https://download.csdn.net/download/aa2528877987/86513333
三、总结
画一个图形主要经历如下四个步骤:
- 1.编写GLSL着色器代码,一个是顶点着色器,一个是片断着色器。
- 2.加载着色器,组成着色器程序。
- 3.创建缓冲区对象,填充缓冲区。
- 4.创建摄像机透视距阵,把元件放到适当的位置。
- 5.给着色器中的变量绑定值。
- 6.调用gl.drawArrays,从向量数组中开始绘制。
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