试验二_基本图元生成算法

1、实验二 基本图元的生成算法一、实验目的1、初步了解显示窗口与视区的关系2、掌握OpengGL点、直线、多边形的绘制3、掌握DDAft线生成算法。4、掌握Bresenham直线生成算法二、实验环境硬件要求：PC机，主流配置，最好为独立显卡，显存 512M以上。软件环境：操作系统：Windows XR语言开发工具：VC6.0O三、实验内容与要求1、调出实验一的源代码运行，调整修改使得显示窗口大小改变时，绘制的矩形大小随之改变。如图2-1所示。提示：(1)在main函数里添加注册窗口变化函数glutReshapeFunc(myreshape); (放在 glutMainLoop()之前)(2)在程序

2、中添加窗口改变子函数，参数 w,h为当前显示窗口的宽和高 void myreshape(GLsizei w, GLsizei h)glViewport(0,0,w,h); /设置视区位置glMatrixMode(GL_PROJECTION);设置投影变换模式glLoadIdentity(); /调单位矩阵，清空当前矩阵堆栈if(w=h)gluOrtho2D(0,300,0,300*(GLfloat)h/(GLfloat)w); /设置裁剪窗口大小 elsegluOrtho2D(0,300*(GLfloat)w/(GLfloat)h,0,300);a)显示窗口改变前b)显示窗口变大后图2-1未修

3、改前的初始源程序参考如下：/*my first program.cpp*/#include void display(void) glClear(GL_COLOR_BUFFER_BIT); / 刷新颜色缓冲区glRectf(0,0,0.5,0.5);glFlush(); /用于刷新命令队列和缓冲区，使所有尚未被执行的OpenG命令得到执行void main(int argc, char* argv)glutInit(&argc, argv); /初始化 GLU1WglutInitDisplayMode(GLUT_SINGLE|GLUT_RGB); /设置显示模式glutInitWindowSi

4、ze(100, 200);glutCreateWindow(hello); /创建窗口，标题为 “ hello ”glutDisplayFunc(display); /用于绘制当前窗口glutMainLoop(); /表示开始运行程序，用于程序的结尾 2、自己参照讲义或教材按照自己的构思画二维平面图形，修改样本程序circle-algorithm.cpp将上面的矩形替换成自己构思的二维平面图形。注意顶点的顺序。参考函数：(1)、点绘制举例glPointSize(2.0) /点的大小设置glBegin(GL_POINTS);glColor3f(1.0,1.0,1.0);glVertex2f(-0

5、.5,-0.5); /顶点glColor3f(1.0,0.0,1.0);glVertex2f(-0.5,0.5);glColor3f(0.0,1.0,1.0);glVertex2f(0.5,0.5);glColor3f(1.0,1.0,0.0);glVertex2f(0.5,-0.5);glEnd()(2)、直线/三角形/四边形绘制举例glLineWidth(2.0);glBegin(GL_LINES);/ glBegin(GL_LINE_STRIP);/ glBegin(GL_LINE_LOOP);/ glBegin(GL_TRIANGLES);/ glBegin(GL_TRIANGLE_S

6、TRIP);/ glBegin(GL_TRIANGLE_FAN);/ glBegin(GL_QUADS);/ glBegin(GL_TRIANGLE_STRIP);glVertex2f(-0.5,0.5);glVertex2f(-0.5,-0.5);glColor3f(1.0,1.0,1.0);glVertex2f(-0.5,0.5);glColor3f(1.0,1.0,0.0);glVertex2f(0.5,-0.5);glEnd();(3)、多边形举例glBegin(GL_POLYGON);glVertex2f(-0.5,0.5);glVertex2f(-0.5,-0.5);glColor

7、3f(1.0,1.0,1.0);glVertex2f(0,-0.5);glColor3f(1.0,1.0,0.0);glVertex2f(0.5,-0.5);glVertex2f(0.5,0.5);glEnd();3、读懂DDAft线生成算法伪代码，并修改伪代码，使之变成可行的OpenGL 代码，验证DDAft线生成算法。DDAft线生成伪代码/x0,y0表示直线的起始点，x1,y1表示直线的终止点，color表示直线的绘制颜色void DDA_line(int x0, int y0, int x1, int y1,int color)int dx = x1 - x0, dy = y1 - y

8、0, k;float xIncrement , yIncrement ,steps, x = x0, y = y0; if (abs (dx) abs (dy)steps = abs (dx);else steps = abs (dy);xIncrement = (float) (dx) /steps;yIncrement = (float) (dy) /steps;for (k =0; k=1的情况，又有斜率|k|1的情况，你可 以使用学过的画直线方法，如DD序法。阅读样本程序，参见circle-algorithm.cpp :附：样本程序 circle-algoritm.cpp#includ

9、e #include #include #include / set some initial parameters, such as the center of the circle(cx,cy), the radius of the circle,int cx=150,cy=150,radius=80;void DDA_Line(int x1,int y1,int x2,int y2);void Bresenham_DrawLine(int x1,int y1,int x2,int y2);void NSidedPolygon( int n, int cx, int cy, int rad

10、ius);void Display( void );void Reshape( int w, int h);int main( int argc, char * argv)(glutInit(&argc, argv);glutInitWindowPosition(0, 0);glutInitWindowSize(window_width, window_height);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);glutCreateWindow(Circle Generation Algorithm);glutDisplayFunc(Display);glutReshapeFunc(Reshape);glutMainLoop();return 0;)void Display( void )(/* YOUR CODE HERE */glutSwapBuffers();)void Reshape( int w, int h)glMatrixMode(GL_PROJECTION);glLoadIdentity();glViewport(0, 0, w, h);gluOrtho2D(0, w, 0, h);/ glutPostRedisplay();void DDA_Line(int x1,int y1,int x2,int y2