Question

我正在尝试绘制一个简单的立方体，并沿着左箭头键和右键向下移动（分别向左和向右）。我不知道gluOrtho2d（leftortho，rightortho，bottomortho，toportho）。我用六个参数尝试了glOrtho（leftortho，rightortho，bottomortho，toportho，-1.0,1.0）但结果是一样的。立方体移动到右上角并消失..我在这方面需要帮助..

double leftortho=5.0,rightortho=1.0,bottomortho=5.0,toportho=1.0;

void init(void) 
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glShadeModel (GL_FLAT);
}

void display(void)
{
    glClear (GL_COLOR_BUFFER_BIT);
    glColor3f (1.0, 1.0, 1.0);
    glutWireCube (1.0);

    gluOrtho2D(leftortho,rightortho,bottomortho,toportho);
    glFlush ();
}

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

float move_unit = 0.001;
void keyboardown(int key, int x, int y)
{
    switch (key)
    {
    case GLUT_KEY_RIGHT:
        {
        leftortho+=move_unit;
        rightortho+=move_unit;
        //bottomortho+=move_unit;
        //toportho+=move_unit;

        break;
        }

    case GLUT_KEY_LEFT:
        {
        leftortho-=move_unit;
        rightortho-=move_unit;
        //bottomortho-=move_unit;
        //toportho-=move_unit;

        break;
        }

    case GLUT_KEY_UP:
        //posY+=move_unit;;
        break;

    case GLUT_KEY_DOWN:
        // posY-=move_unit;;
        break;

    default:
        break;
    }
    glutPostRedisplay();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize (500, 500); 
    glutInitWindowPosition (100, 100);
    glutCreateWindow (argv[0]);
    init ();
    glutDisplayFunc(display); 
    glutReshapeFunc(reshape);
    glutSpecialFunc(keyboardown);
    glutMainLoop();
    return 0;
}

Answer 1

试一试：

#include <GL/glut.h>

double leftortho=-1.0;
double rightortho=1.0;
double bottomortho=-1.0;
double toportho=1.0;
float move_unit = 0.01;
void keyboardown(int key, int x, int y)
{
    switch (key)
    {
    case GLUT_KEY_RIGHT:
        leftortho-=move_unit;
        rightortho-=move_unit;
        break;

    case GLUT_KEY_LEFT:
        leftortho+=move_unit;
        rightortho+=move_unit;
        break;

    case GLUT_KEY_UP:
        toportho-=move_unit;
        bottomortho-=move_unit;
        break;

    case GLUT_KEY_DOWN:
        toportho+=move_unit;
        bottomortho+=move_unit;
        break;

    default:
        break;
    }
    glutPostRedisplay();
}

void display(void)
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glShadeModel (GL_FLAT);

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    glOrtho(leftortho,rightortho,bottomortho,toportho, -10, 10);

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    glColor3f (1.0, 1.0, 1.0);
    glutWireCube (1.0);

    glutSwapBuffers();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize (500, 500); 
    glutInitWindowPosition (100, 100);
    glutCreateWindow (argv[0]);
    glutDisplayFunc(display); 
    glutSpecialFunc(keyboardown);
    glutMainLoop();
    return 0;
}

Answer 2

我认为问题在于你在调用gluOrtho2d()之前没有重置投影矩阵，所以你的行动正在积累。我想你需要这样做：

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2d(left,right,bottom,top);

另请注意，您的左侧和右侧似乎是交换的，您的底部和顶部也是如此。这是合法的，但它可能最终导致左右箭头键看起来相反。它基本上将你的转变设置为倒退和颠倒。

打开GL设置正交投影

2 个答案: