Question

我正在尝试根据鼠标输入坐标绘制一条线。

但是，以下代码编译时，不会从鼠标输入中显示一行。

int coord_1[2]; //(x,y) of first point for line
int coord_2[2]; //(x,y) of second point for line
bool ready_1=false;
bool ready_2=false;

void drawLine()
{
  glBegin(GL_LINES);
     glColor3f(1.0, 0.0, 0.0);
     glVertex2f(coord_1[0], coord_1[1]);
     glVertex2f(coord_2[0], coord_2[1]);
  glEnd();
}

void display(void) 
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-1,1,-1,1,-1,1);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    if(ready_1 && ready_2)
    {
       drawLine();
       ready_1 = ready_2 = false;
    }
    glutSwapBuffers();
}

void mouse(int button, int state, int x, int y)
{
   switch (button) 
   {
      case GLUT_RIGHT_BUTTON:
         if (state == GLUT_DOWN) //button pressed down
         {
            //only do something on release
         }
         if (state == GLUT_UP) //released button
         {
            cout << "right button up" << endl;
         }
         break;
      case GLUT_LEFT_BUTTON:
         if (state == GLUT_DOWN) //button pressed down
         {
            coord_1[0]=x;
            coord_2[1]=y;
            cout << "first pos" << endl;
            ready_1=true;
          }
          if (state == GLUT_UP) //released button
          {
            coord_2[0]=x;
            coord_2[1]=y;
            cout << "second pos" << endl;
            ready_2=true;
          }
          break;

      default:
          break;
  }
}

int main(int argc, char **argv) 
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH|GLUT_DOUBLE|GLUT_RGBA|GLUT_MULTISAMPLE);

    glutInitWindowPosition(100,100);
    glutInitWindowSize(512,512);
    glutCreateWindow("Asn 1");

    glutDisplayFunc(display);
    glutIdleFunc(display);

    glutMouseFunc(mouse);
    glutKeyboardFunc(processNormalKeys);

    //  GLUT main loop
    glutMainLoop();

   return(0);
}

正确方向的任何帮助或指示？

Answer 1

你可能画了一条线，但是既然你之后重新设置了绘图条件，那么你的线会在下一个绘制步骤中被隐藏（这可能非常快）。

删除ready_1 = ready_2 = false;，该行应保持可见。相反，您可以在收到左键按下事件时设置ready_2 = false。

从鼠标输入中未显示openGL / Glut绘制的线条

1 个答案: