如何在opengl中绘制平滑/消除锯齿的圆圈？

Question

如何在opengl中绘制平滑/消除锯齿的圆圈？我正在使用glBegin（GL_LINE_LOOP）;绘制我的圆圈，但不顺利。 我启用了：

glEnable( GL_LINE_SMOOTH );
glHint( GL_LINE_SMOOTH_HINT, GL_NICEST );
glEnable(GL_BLEND); 
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

Answer 1

This is years late, but the way I did it was using this tutorial.

但是，这仅适用于GL_POINTS。

为此，您还需要启用OES_standard_derivatives扩展程序。

顶点：

attribute mediump vec4 Position;
attribute lowp float Size;

void main(void) {
    gl_Position = Position;
    gl_PointSize = Size;
}

片段：

#extension GL_OES_standard_derivatives : enable

void main(void) {
    lowp vec2 cxy = 2.0 * gl_PointCoord - 1.0;
    lowp float radius = dot(cxy, cxy);
    lowp float delta = fwidth(radius);
    lowp float alpha = 1.0 - smoothstep(1.0 - delta, 1.0 + delta, radius);
    gl_FragColor = vec4(1.0, 1.0, 1.0, alpha);
}