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JavaScript微信小游戏中three.js离屏画布的示例代码

发布时间: 2021年1月13日 | 浏览: | 分类:js开发

国庆8天长假，重庆之行因故未成，偶得闲，用three.js结合cannon.js写个3D小游戏耍耍。在微信小游戏中，把three.js的3D内容在离屏画布处理，然后复制到在屏画布，方法是：
let c_toolbarHeight=140;

let sysInfo=wx.getSystemInfoSync();
require('./js/libs/weapp-adapter.js');
var canvas_webGL=window.canvas;
canvas_webGL.width = sysInfo.screenWidth * sysInfo.pixelRatio;
canvas_webGL.height = (sysInfo.screenHeight-c_toolbarHeight) * sysInfo.pixelRatio;
var ctx_webGL=canvas_webGL.getContext('webgl');

let options={context: ctx_webGL}
let renderer = new THREE.WebGLRenderer(options);
renderer.setSize(sysInfo.screenWidth, sysInfo.screenHeight-c_toolbarHeight);
renderer.setPixelRatio(sysInfo.pixelRatio);

function render(){

//清除canvas_bkg的3D区域

wx.tmGlobal.eraseZone(0,

c_toolbarHeight,

sysInfo.screenWidth,

sysInfo.screenHeight);

renderer.render(scene, camera);

wx.tmGlobal.ctx_bkg.drawImage(canvas_webGL,

0,c_toolbarHeight*sysInfo.pixelRatio);

//画一条横的红线

wx.tmGlobal.ctx_bkg.strokeStyle = '#FF8C00';

wx.tmGlobal.ctx_bkg.lineWidth = 2;

wx.tmGlobal.ctx_bkg.beginPath();

wx.tmGlobal.ctx_bkg.moveTo(0,

(c_toolbarHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.lineTo(

sysInfo.screenWidth*sysInfo.pixelRatio,

(c_toolbarHeight)*sysInfo.pixelRatio);

//画游戏结束临界线

wx.tmGlobal.ctx_bkg.moveTo(0,

(c_toolbarHeight+c_yugaoHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.lineTo(

sysInfo.screenWidth*sysInfo.pixelRatio,

(c_toolbarHeight+c_yugaoHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.stroke();

//把canvas_bkg画到在屏画布

wx.tmGlobal.ctx_main.clearRect(0,0,

wx.tmGlobal.canvas_main.width,wx.tmGlobal.canvas_main.height);

wx.tmGlobal.ctx_main.drawImage(wx.tmGlobal.canvas_bkg,0,0);
}
let c_toolbarHeight=140;

let sysInfo=wx.getSystemInfoSync();
require('./js/libs/weapp-adapter.js');
var canvas_webGL=window.canvas;
canvas_webGL.width = sysInfo.screenWidth * sysInfo.pixelRatio;
canvas_webGL.height = (sysInfo.screenHeight-c_toolbarHeight) * sysInfo.pixelRatio;
var ctx_webGL=canvas_webGL.getContext('webgl');

let options={context: ctx_webGL}
let renderer = new THREE.WebGLRenderer(options);
renderer.setSize(sysInfo.screenWidth, sysInfo.screenHeight-c_toolbarHeight);
renderer.setPixelRatio(sysInfo.pixelRatio);

function render(){

//清除canvas_bkg的3D区域

wx.tmGlobal.eraseZone(0,

c_toolbarHeight,

sysInfo.screenWidth,

sysInfo.screenHeight);

renderer.render(scene, camera);

wx.tmGlobal.ctx_bkg.drawImage(canvas_webGL,

0,c_toolbarHeight*sysInfo.pixelRatio);

//画一条横的红线

wx.tmGlobal.ctx_bkg.strokeStyle = '#FF8C00';

wx.tmGlobal.ctx_bkg.lineWidth = 2;

wx.tmGlobal.ctx_bkg.beginPath();

wx.tmGlobal.ctx_bkg.moveTo(0,

(c_toolbarHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.lineTo(

sysInfo.screenWidth*sysInfo.pixelRatio,

(c_toolbarHeight)*sysInfo.pixelRatio);

//画游戏结束临界线

wx.tmGlobal.ctx_bkg.moveTo(0,

(c_toolbarHeight+c_yugaoHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.lineTo(

sysInfo.screenWidth*sysInfo.pixelRatio,

(c_toolbarHeight+c_yugaoHeight)*sysInfo.pixelRatio);

wx.tmGlobal.ctx_bkg.stroke();

//把canvas_bkg画到在屏画布

wx.tmGlobal.ctx_main.clearRect(0,0,

wx.tmGlobal.canvas_main.width,wx.tmGlobal.canvas_main.height);

wx.tmGlobal.ctx_main.drawImage(wx.tmGlobal.canvas_bkg,0,0);
}在vivo和iphone手机都表现正常，但是，华为手机显示不出来：https://developers.weixin.qq.com/community/develop/doc/00026c3c1c8eb010de384a82d51000?jumpto=其它用户也提了好久了，腾讯或华为都没有解决，试来试去，终于找到了另一种写法：
renderer = new THREE.WebGLRenderer();
let target = new THREE.WebGLRenderTarget(

sysInfo.screenWidth*sysInfo.pixelRatio,

(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio);
renderer.setRenderTarget(target);
gl=renderer.getContext();

var canvas_huawei=wx.createCanvas();
canvas_huawei.width=sysInfo.screenWidth*sysInfo.pixelRatio;
canvas_huawei.height=(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio;
var ctx_huawei=canvas_huawei.getContext('2d');

var canvas_huawei2=wx.createCanvas();
canvas_huawei2.width=sysInfo.screenWidth*sysInfo.pixelRatio;
canvas_huawei2.height=(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio;
var ctx_huawei2=canvas_huawei2.getContext('2d');

var imageData = ctx_huawei.createImageData(

sysInfo.screenWidth*sysInfo.pixelRatio,

(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio);
var pixels = new Uint8Array(imageData.data.length);

function render(){

//擦除背景画布的webGL区域（因为webGL是用的透明绘制）

wx.tmGlobal.eraseZone(0,

c_toolbarHeight,

sysInfo.screenWidth,

sysInfo.screenHeight);

renderer.render(scene, camera);

gl.readPixels(

0,

0,

gl.drawingBufferWidth,

gl.drawingBufferHeight,

gl.RGBA,gl.UNSIGNED_BYTE,pixels);

imageData.data.set(pixels);

ctx_huawei.putImageData(imageData,0,0);

//清除

ctx_huawei2.clearRect(0,0,canvas_huawei2.width,canvas_huawei2.height);

//上下镜像翻转

ctx_huawei2.translate(0,canvas_huawei2.height);

ctx_huawei2.scale(1, -1);

ctx_huawei2.drawImage(canvas_huawei,0,0);

//恢复

ctx_huawei2.translate(0,canvas_huawei2.height);

ctx_huawei2.scale(1, -1);

wx.tmGlobal.ctx_bkg.drawImage(canvas_huawei2,

0,c_toolbarHeight*sysInfo.pixelRatio);

......
}
renderer = new THREE.WebGLRenderer();
let target = new THREE.WebGLRenderTarget(

sysInfo.screenWidth*sysInfo.pixelRatio,

(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio);
renderer.setRenderTarget(target);
gl=renderer.getContext();

var canvas_huawei=wx.createCanvas();
canvas_huawei.width=sysInfo.screenWidth*sysInfo.pixelRatio;
canvas_huawei.height=(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio;
var ctx_huawei=canvas_huawei.getContext('2d');

var canvas_huawei2=wx.createCanvas();
canvas_huawei2.width=sysInfo.screenWidth*sysInfo.pixelRatio;
canvas_huawei2.height=(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio;
var ctx_huawei2=canvas_huawei2.getContext('2d');

var imageData = ctx_huawei.createImageData(

sysInfo.screenWidth*sysInfo.pixelRatio,

(sysInfo.screenHeight-c_toolbarHeight)*sysInfo.pixelRatio);
var pixels = new Uint8Array(imageData.data.length);

function render(){

//擦除背景画布的webGL区域（因为webGL是用的透明绘制）

wx.tmGlobal.eraseZone(0,

c_toolbarHeight,

sysInfo.screenWidth,

sysInfo.screenHeight);

renderer.render(scene, camera);

gl.readPixels(

0,

0,

gl.drawingBufferWidth,

gl.drawingBufferHeight,

gl.RGBA,gl.UNSIGNED_BYTE,pixels);

imageData.data.set(pixels);

ctx_huawei.putImageData(imageData,0,0);

//清除

ctx_huawei2.clearRect(0,0,canvas_huawei2.width,canvas_huawei2.height);

//上下镜像翻转

ctx_huawei2.translate(0,canvas_huawei2.height);

ctx_huawei2.scale(1, -1);

ctx_huawei2.drawImage(canvas_huawei,0,0);

//恢复

ctx_huawei2.translate(0,canvas_huawei2.height);

ctx_huawei2.scale(1, -1);

wx.tmGlobal.ctx_bkg.drawImage(canvas_huawei2,

0,c_toolbarHeight*sysInfo.pixelRatio);

......
}

原文地址：http://www.chinasgp.cn/article/3410.html

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JavaScript微信小游戏中three.js离屏画布的示例代码-js开发