如何在WebGL中清除矩形区域？ [英] How to clear a rectangle area in WebGL?

问题描述

WebGL具有 clear 方法，可清除整个表面。仅清除表面的特定矩形的最佳方法是什么？例如，我想将一个像素为100x100的框（从（50，50）开始）设置为全零（ARGB 0、0、0、0）。我现在所能想到的就是绘制一个带有片段着色器的四边形，该着色器写入零。有没有更简单的方法？

WebGL has a clear method that clears an entire surface. What's the best way to clear just a particular rectangle of the surface? For example I want to set a 100x100 box of pixels starting at (50, 50) to all zeroes (ARGB 0, 0, 0, 0). All I can think of right now is drawing a quad with a fragment shader that writes zeroes. Is there not an easier way?

推荐答案

您可以使用SCISSOR测试将清除（和渲染）限制为一个矩形

You can use the SCISSOR test to constrain clearing (and rendering in general) to a rectangle.

// turn on the scissor test.
gl.enable(gl.SCISSOR_TEST);

// set the scissor rectangle.
gl.scissor(x, y, width, height);

// clear.
gl.clearColor(r, g, b, a);
gl.clear(gl.COLOR_BUFFER_BIT ...);

// turn off the scissor test so you can render like normal again.
gl.disable(gl.SCISSOR_TEST);

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