查找正多边形的顶点
我有一些由用户定义的属性，然后我想使用它们自动生成正多边形。属性包括中心 x、中心 y、半径和顶点数。我想知道如何计算正多边形所有顶点的x和y坐标。我已经尝试过计算正多边形顶点的坐标 讨论。但它总是给我错误的坐标。我当前的代码如下（C++）：
#define DOUBLE(a) ((a)*(a))
...
if(radius <= 0 || vertices < 3)
return NULL;
Polygon* poly = new Polygon;
double angle = DOUBLE(M_PI) / vertices;
for(long i = 0; i < vertices; i++)
{
double a = (angle * i);
poly->add(centerX + radius * cos(a), centerY + radius * sin(a));
}
return poly;
I have some properties defined by the user, and then I want use them to automatically generate a regular polygon. The properties are centre x, centre y, radius and number of vertices. I would like to know how to calculate the x and y coordinates of all vertices of a regular polygon. I've already tried to do as Calculate coordinates of a regular polygon's vertices discussion. But it always gives me thw wrong coordinates. My current code is as follows (C++):
#define DOUBLE(a) ((a)*(a))
...
if(radius <= 0 || vertices < 3)
return NULL;
Polygon* poly = new Polygon;
double angle = DOUBLE(M_PI) / vertices;
for(long i = 0; i < vertices; i++)
{
double a = (angle * i);
poly->add(centerX + radius * cos(a), centerY + radius * sin(a));
}
return poly;
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评论（2）
你的角度计算有错误。
每个顶点之间的角度应为
2 * M_PI / vertices。显然你的宏：
不正确。
然而，在 C++ 中，无论如何，您确实不应该使用宏来进行此类琐碎的操作 - 它最多应该是一个内联函数，或者只是上面给出的直接公式。
There's an error in your angle calculation.
The angle between each vertex should be
2 * M_PI / vertices.Obviously your macro:
is incorrect.
However in C++ you really shouldn't use macros for such trivial operations anyway - it should at the very most be an inline function, or just the direct formula given above.
尝试一下
，或者
您正在以虚假身份定义 SQUARE(a) 。
Try
or
You are defining SQUARE(a) under a false identity.