计算机图形学（二）输出图元_19_显示窗口重定形函数

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glutReshapeFunc(winReshapeFcn);

       作为一个例子，下列程序展示了怎样构造winReshapeFcn过程。命令glLoadIdentity包含在重定形函数中，从而使前面任意的投影参数值对新的投影设置不起作用。该程序显示了讨论的规则六边形。尽管本例中的六边形中心(在圆的中心位置)用显示窗口参数的概念描述，但是该六边形的位置不受显示窗口尺寸的任何改变的影响。这是因为六边形在显示表中定义，并且仅仅是最初的中心坐标存储在表中。如果希望在改变显示窗口尺寸时改变六边形的位置，则需要使用另一种方法来定义六边形或改变显示窗口的坐标参考。图3.64给出了该程序的输出。

#include <GL/glut.h>
#include <math.h>
#include <stdlib.h>

const double TWO_PI = 6.2831853;

/* Intial display-window size.*/
GLsizei winWidth = 400, winHeight = 400;
GLuint regHex;

class screenPt
{
   private:
       GLint x,y;
	public:
	/* Default Constructor: initializes coordinate position to (0, 0).*/
	screenPt ( ) {
	   x = y = 0;
	}
	void setCoords (GLint xCoord, GLint yCoord) {
	   x = xCoord;
	   y = yCoord;
	}
	GLint getx () const {
	   return x;
	}
	GLint gety () const {
	   return y;
	}
};
static void init (void)
{
    screenPt hexVertex, circCtr;
	GLdouble theta;
	GLint k;
	
	/* Set circle center coordinates.*/
	circCtr.setCoords (winWidth / 2, winHeight/2);
	
	glClearColor (1.0, 1.0, 1.0, 0.0);//Display-window color = white.
	
	/* Set up a display list for a red regular hexagon.
	 * Vertices for the hexagon are Six equally spaced
	 * points around the circumference of a circle.
	 */
	 regHex = glGenLists (1); // Get an identifier for the display list.
	 glNewList (regHex, GL_COMPILE);
	    glColor3f (1.0, 0.0, 0.0); // Set fill color for hexagon to red.
		glBegin (GL_POLYGON);
		    for (k = 0; k < 6; k++){
		    theta = TWO_PI * k / 6.0;
		        hexVertex.setCoords (circCtr.getx () + 150 * cos (theta), circCtr.gety () + 150 * sin (theta));    
		        glVertex2i (hexVertex.getx (), hexVertex.gety ());
		    }
	    glEnd ();
	glEndList ();
}
void regHexagon (void)
{
    glClear (GL_COLOR_BUFFER_BIT);
	glCallList (regHex);
	glFlush();
}

void winReshapeFcn (int newWidth, int newHeight)
{
    glMatrixMode (GL_PROJECTION);
	glLoadIdentity ( );
	gluOrtho2D (0.0, (GLdouble) newWidth, 0.0, (GLdouble) newHeight);
	
	glClear (GL_COLOR_BUFFER_BIT);
}

void main (int argc, char** argv)
{
    glutInit (&argc, argv);
	glutInitDispayMode (GLUT_SINGLE | GLUT_RGB);
	glutInitWindowPosition (100, 100);
	glutInitWindowSize (winWidth, winHeight);
	glutCreateWinow ("Reshape-Function & Display-List Example");
	
	init ( );
	glutDisplayFunc (regHexagon);
	glutReshapeFunc (winReshapeFcn);
	
	glut MainLoop ();
}

计算机图形学（二）输出图元_19_显示窗口重定形函数

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原文地址：http://blog.csdn.net/heyuchang666/article/details/51597561