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);}

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); ......}

到此这篇关于微信小游戏中three.js离屏画布的示例代码的文章就介绍到这了,更多相关微信小游戏three.js离屏画布内容请搜索以前的文章或继续浏览下面的相关文章希望大家以后多多支持！