计算机图形学 几何变换代码
实现矩形在窗口内沿着水平线匀速移动
/*
* double.c
* This is a simple double buffered program.
* Pressing the left mouse button rotates the rectangle.
* Pressing the right mouse button stops the rotation.
*/
/*#include <GL/glut.h>
#include <stdlib.h>
static GLfloat spin = 0.0;
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
//glRotatef(spin, 0.0, 0.0, 1.0);
glTranslatef (spin, 0.0, 0.0);
glColor3f(1.0, 1.0, 1.0);
glRectf(-10.0, -10.0, 10.0, 10.0);
glPopMatrix();
glutSwapBuffers();
}
void spinDisplay(void)
{
spin = spin + 0.5;//控制平移的速度
if (spin > 360.0)
spin = spin - 360.0;
glutPostRedisplay();
}
void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel (GL_FLAT);
}
void reshape(int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);/*函数void glOrtho(left,right,bottom,top,near,far)：
设置投影方式为正交投影（平行投影），其取景体积是一个各面均为矩形的六面体;*/
/* glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void mouse(int button, int state, int x, int y)
{
switch (button) {
case GLUT_LEFT_BUTTON:
if (state == GLUT_DOWN)
glutIdleFunc(spinDisplay);
break;
case GLUT_MIDDLE_BUTTON:
case GLUT_RIGHT_BUTTON:
if (state == GLUT_DOWN)
glutIdleFunc(NULL);
break;
default:
break;
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (100, 100);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMainLoop();
return 0; /* ANSI C requires main to return int. */
3、已知某三角形的三顶点坐标为{50.0,25.0},{150.0,25.0},{100.0,100.0}。
要求：（1）创建一个长宽分别为600、600的窗口，窗口的左上角位于屏幕坐标（100，100）处。（提示：请试着修改gluOrtho2D函数参数，使得绘制的三角形尽可能居中显示）
代码如下：
#include <GL/glut.h>
#include <stdlib.h>
void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel (GL_FLAT);
}
void draw_triangle(void)
{
glBegin (GL_LINE_LOOP);
glVertex2f(0.0, 25.0);
glVertex2f(25.0, -25.0);
glVertex2f(-25.0, -25.0);
glEnd();
}
void display(void)
{
glClear (GL_COLOR_BUFFER_BIT);
glColor3f (1.0, 1.0, 1.0);
glLoadIdentity ();
glColor3f (1.0, 1.0, 1.0);
draw_triangle ();
glEnable (GL_LINE_STIPPLE);
glLineStipple (1, 0xF0F0);
glLoadIdentity ();
glTranslatef (-20.0, 0.0, 0.0);
draw_triangle ();
glLineStipple (1, 0xF00F);
glLoadIdentity ();
glScalef (1.5, 0.5, 1.0);
draw_triangle ();
glLineStipple (1, 0x8888);
glLoadIdentity ();
glRotatef (90.0, 0.0, 0.0, 1.0);
draw_triangle ();
glDisable (GL_LINE_STIPPLE);
glFlush ();
}
void reshape (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
//glViewport ( w, h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
if (w <= h)
gluOrtho2D (-200.0, 200.0, -200.0*(GLfloat)h/(GLfloat)w,
200.0*(GLfloat)h/(GLfloat)w);//决定显示世界窗口中的那一部分内容，使用世界左边表示（左，右，下，上）
else
gluOrtho2D (-200.0*(GLfloat)w/(GLfloat)h,
200.0*(GLfloat)w/(GLfloat)h, -200.0, 200.0);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (600, 600); //创建一个长宽分别为600、600的窗口，
glutInitWindowPosition (100, 100);//窗口的左上角位于屏幕坐标（100，100）处。
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
运行结果为：
}