C ++：在OpenGL中绘制2D磁盘 [英] C++: Drawing a 2D disk in OpenGL

问题描述

我试图写一个适当的函数，使用OpenGL在屏幕上绘制2D光盘几天，我根本看不出来：（

这是我当前的代码：

  void Disk（Float x，Float y，Float r，const Color& ; vColor）
 {
 glBegin（GL_TRIANGLE_FAN）; 
 glVertex2f（x，y）; 
（Float i = 0; i <= 2 * PI + 0.1; i + = 0.1）
 {
 glVertex2f（x + sin（i）* r，y + cos（i）* r）; 
} 
 glEnd（）; 
} 
  

放大时，生成的磁盘显示峰值，而不是边缘， 。

此函数不仅绘制一个磁盘，而且始终多于一个 - 这意味着如果启用了alpha，则结果会出错。 p>

• 我需要在我的函数中更改哪些内容才能正确绘制磁盘？

解决方案

  void circle（float x，float y，float r，int segments）
 {
 glBegin（GL_TRIANGLE_FAN）; 
 glVertex2f（x，y）; 
 for（int n = 0; n <= segments; ++ n）{
 float const t = 2 * M_PI *（float）n / 
 glVertex2f（x + sin（t）* r，y + cos（t）* r）; 
} 
 glEnd（）; 
} 
  

关于尖峰...一张图片可以讲一千个字。

I've tried to write a proper function for drawing a 2D disk on the screen with OpenGL for a few days now, and I simply can't seem to get it right :(

This is my current code:

void Disk( Float x, Float y, Float r, const Color& vColor )
{
    glBegin( GL_TRIANGLE_FAN );
        glVertex2f( x, y );
        for( Float i = 0; i <= 2 * PI + 0.1; i += 0.1 )
        {
            glVertex2f( x + sin( i ) * r, y + cos( i ) * r );
        }
    glEnd();
}

When zooming in, the resulting disk shows spikes, not as in edges but really spikes pointing out.

Also the function doesn't draw one disk only, but always a bit more than one - which means that if alpha is enabled, the results look wrong.

• What do I need to change in my function so it properly draws a disk?

解决方案

void circle(float x, float y, float r, int segments)
{
    glBegin( GL_TRIANGLE_FAN );
        glVertex2f(x, y);
        for( int n = 0; n <= segments; ++n ) {
            float const t = 2 * M_PI * (float)n / (float)segments;
            glVertex2f(x + sin(t) * r, y + cos(t) * r);
        }
    glEnd();
}

that should get you rid of the overdraw. About the spikes... a picture could tell a thousand words.

这篇关于C ++：在OpenGL中绘制2D磁盘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！