为什么WebGL“清除"吸引前端缓冲区? [英] Why WebGL 'clear' draw to front buffer?
问题描述
为什么不需要交换缓冲区或glFinish?
Why no need for swap-buffers or glFinish?
<!DOCTYPE html>
<html>
<head>
<title>Game v.0.0</title>
<script>
var gl = null;
function startGame()
{ { var canvas = document.getElementById('gameCanvas');
var glNames = ["webgl", "experimental-webgl", "webkit-3d", "moz-webgl"];
for (var glNameI = 0; glNameI < glNames.length; ++glNameI)
try
{ gl = canvas.getContext(glNames[glNameI]);
if (gl) break;
}
catch(e)
{}
if(!gl)
{ canvas.outerHTML = "<a>WebGL NOT SUPPORTED? :(</a>";
return;
}
}
window.onkeydown = function(ev)
{ switch(ev.keyCode)
{
case 49:// 1 key
gl.clearColor(0.3,0.7,0.2,1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
break;
case 50:// 2 key
gl.clearColor(0.3,0.2,0.7,1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
break;
}
};
}
</script>
<style type="text/css">
canvas {border: 2px dotted blue;}
</style>
</head>
<body onload="startGame()">
<div><canvas id="gameCanvas" width="640" height="480"></canvas></div>
</body>
</html>
推荐答案
因为这是WebGL的工作方式.
Because that's the way WebGL works.
WebGL自动交换/复制.每当您执行任何会影响WebGL drawingBuffer(例如"backbuffer")的操作时，都会将其标记为交换/复制.下一次浏览器合成网页时，它将执行交换或复制操作.您可以告诉它始终复制.无法告诉它总是交换
WebGL swaps/copies automatically. Anytime you do anything that effects the WebGL drawingBuffer (think "backbuffer) it gets marked to swap/copy. The next time the browser composites the web page it will do either a swap or a copy. You can tell it to always copy. You can not tell it to always swap
具体来说，使用 {preserveDrawingBuffer:true} 来创建WebGL上下文，如
Specifically, creating the WebGL context with {preserveDrawingBuffer: true} as in
gl = someCanvas.getContext("webgl", {preserveDrawingBuffer: true});
告诉WebGL您始终希望它进行复制.
Tells WebGL you always want it to do a copy.
默认值为WebGL根据各种因素选择交换或复制.例如，如果启用了抗锯齿功能，则它始终始终是一个副本(解决方案)，而仿效处理功能似乎已关闭，则可能是交换.同样，在这种默认情况下，当 preserveDrawingBuffer 执行复制或交换后为false时，它将清除后备缓冲区.这是为了使它看起来是一致的，而不管它是选择复制还是交换.
The default is WebGL chooses swap or copy depending on various factors. For example if anti-aliasing is on it's always effectively a copy (a resolve) where as if anti-aliasing is off it might be a swap. Also, in this default case, when preserveDrawingBuffer is false after it does a copy or swap it will clear the backbuffer. This is to try to make it appear consistent regardless of whether it chooses to copy or swap.
如果 preserveDrawingBuffer = true，则它永远不会清除后备缓冲区.
If preserveDrawingBuffer = true then it never clears the backbuffer.
如果要对多个JavaScript事件进行大量工作，并且在完成所有工作之前不让用户看到结果，则需要渲染到带有附加纹理或渲染缓冲区的帧缓冲区，然后在所有完成工作比渲染到画布(后缓冲区)要好.
If you want to do a bunch of work over multiple JavaScript events and not let the user see the results until all your work is done you'll need to render to a framebuffer with an attached texture or renderbuffer and then when all your work is done render than attachment to the canvas (the backbuffer).
就像 gl.finish 一样，这在WebGL中是无操作的.没有意义.
as for gl.finish that's a no-op in WebGL. It has no point.
这篇关于为什么WebGL“清除"吸引前端缓冲区?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
