Question

大家看看我的程序为什么不能绘制出图来，我想点一下鼠标就在鼠标的位置画个圆

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

float mousex=0,mousey=0;
void init (void)

{

glClearColor (0.0,0.0,0.0,0.0);

gluOrtho2D (0.0,400.0,0.0,300.0);
}

void reshape(int w, int h)
{
glViewport(0, 0,(GLsizei) w, (GLsizei) h);
}

void display(void)

{

glClear(GL_COLOR_BUFFER_BIT) ;

glColor3f(1.0, 0.0, 0.0) ;

glFlush() ;

}

void redisplay(void)

{
int xd=0,yd=0,r=40,x,y,xb,yb,xf,yf,d,x1b,y1b,x1f,y1f;

glTranslatef(mousex,mousey,0);

x=0;

y=r;

d=1-r;

glBegin(GL_POINTS);

while(x<y)

{

if(d<0)

d+=2*x+3;

else

{

d+=2*(x-y)+5;

y--;}

xb=x+xd;//x、y不交换

yb=y+yd;

xf=xd-x;

yf=yd-y;

x1b=y+xd;//交换x、y的处理

y1b=x+yd;

x1f=xd-y;

y1f=yd-x;

glVertex2i(xb, yb);

glVertex2i(xf, yb);

glVertex2i(xb, yf);

glVertex2i(xf, yf);

glVertex2i(x1b, y1b);

glVertex2i(x1f, y1b);

glVertex2i(x1b, y1f);

glVertex2i(x1f, y1f);

x++;}

glEnd();

glFlush() ; }

void keyboard (unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
default:
break;
}
}

void mouse(int button, int state, int x, int y)
{
switch (button) {
case GLUT_LEFT_BUTTON:
if (state == GLUT_DOWN)
{
mousex=x;
mousey=800-y;
redisplay();
}

break;
default:
break;
}
}

int main(int argc, char **argv)
{

glutInit(&argc, argv) ;

glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB) ;

glutInitWindowSize(400, 300) ;

glutCreateWindow("tjf06") ;

glutFullScreen();

init() ;
glutMouseFunc(mouse);

glutReshapeFunc(reshape);

glutDisplayFunc(display) ;

glutKeyboardFunc(keyboard);

glutMainLoop() ;

return 0 ;
}
opengl中glTranslatef函数是不是不能用变量作参数啊 ，为什么我一把mousex和mousey两个变量作为他的参数就不能绘出图来，直接用数字就可以？

Answer 1

glTranslatef函数可世败以用变量祥返蠢作参数的
mousex和mousey要有初值的。
试试把 redisplay()放在glutDisplayFunc(display) 里，似乎是循环中没有成功调用执谨陪行 redisplay();