计算机图形学（二）输出图元_20_章节总结_程序展示_饼图

饼图用来给出整体中各部分的分布比例。使用中点圆算法子程序来构造一个饼图。例子中的值用于确定扇形的数量和大小，

该程序的输出请参见图3.69。

#include 
#include 
#include 


const gldouble twopi = 6.283185;


class scrpt {
public:
    glint x, y;
};


glsizei winwidth = 400, winheight = 300; // initial display window size.


void init (void)
{
    glclearcolor (1.0, 1.0, 1.0, 1.0);
	glmatrixmode (gl_projection);
	gluortho2d (0.0, 200.0, 0.0, 150.0);
}
    .
	.                                    // midpoint routines for displaying a circle.
	.
	
void piechart (void)
{
    scrpt circctr, piept;
	glint radius = winwidth / 4;         // circle radius.
	
	gldouble sliceangle, previoussliceangle = 0.0;
	
	glint k, nslices = 12;               // number of slices.
	glfloat datavalues[12] = {10.0, 7.0, 13.0, 5.0, 13.0, 14.0, 3.0, 16.0, 5.0, 3.0, 17.0, 8.0};
	glfloat datasum = 0.0;
	circctr.x = winwidth / 2;            // circle center position.
	circctr.y = winheight / 2;
	circlemidpoint (circctr, radius);    // call a midpoint circle-plot routine.
	for (k = 0; k