基本上有三个选项画一个圆圈。你不指定是否要固/薄/厚等等看，所以不是所有的这些可能是appriopriate为您的情况：

Basically, there are three options for drawing a circle. You don't specify whether you want a solid/thin/thick etc look, so not all of these might be appriopriate for your case:

1. 产生在一个圆圈顶点和使用glDrawArray（GL_LINES，...）。根据你有多少个顶点生成，这将产生一个很好的和清晰的结果。

1. Generate vertices in a circle and use glDrawArray( GL_LINES, ... ). Depending on how many vertices you generate this will yield a nice and crisp result.

使用pgenerated圆（阿尔法透明度）的质地$ P $并将其映射在四。这将导致非常流畅的图形，并允许一个'thick'圈，但它不会像灵活：即使有纹理映射，你会希望你的纹理是关于你正在呈现四相同尺寸

Use a pregenerated texture of a circle (with alpha transparency) and map it on a quad. This will result in very smooth graphics and allow for a ´thick´ circle, but it will not be as flexible: even with mipmapping, you'll want your texture to be about the same size you are rendering the quad.

使用一个片段着色器。如这个例子应该的正常工作。

Use a fragment shader. Examples like this should work fine.