我的绘图存在坐标/glortho 问题

I have made a bit of a change to my code in the last couple of hours as everything was messy with my grid so I made it into a void and I made sure I got the boundary that I was drawn out first as it is now placed where I want it to be, however my grid is now in the wrong place shown in the image below

我认为这是一个荣耀问题，但我不知道要放入什么代码来改变我想要放置绘图的位置。

#include "include\freeglut.h"   // OpenGL toolkit - in the local shared folder
#include <iostream>

using namespace std;

#define X_CENTRE 0.0            /* 0,0 */
#define Y_CENTRE 0.0

#define LENGTH   20.0 

GLboolean grid = false;

int w;
int h;


/* reshape callback function executed when window is moved or resized */
void reshape(int width, int height)
{
h = width;
w = height;
//set the matrix mode to PROJECTION
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, width, height);
// use orthographic (parallel) projection
glOrtho(-200.0, 200.0, -200.0, 200.0, -200.0, 200.0);
//set the matrix mode to MODEL
glMatrixMode(GL_MODELVIEW);

}

void drawGrid() {
GLint i;

glEnable(GL_LINE_STIPPLE); //Activates the line-style feature

glLineStipple(1, 0xAAAA);  // Plots a dashed polyline

glColor3f(0.8, 0.8, 0.8);

if (grid) {
    glBegin(GL_LINES);
    for (i = 2; i <= 9; i++)
    {
        glVertex3f(i * 0.1 * w, 0.0, 0.0);
        glVertex3f(i * 0.1 * w, 0.9 * h, 0.0);
    }

    for (i = 1; i <= 9; i++)
    {
        glVertex3f(0.1 * w, i * 0.1 * h, 0.0);
        glVertex3f(w, i * 0.1 * h, 0.0);
    }
    glEnd();
    glDisable(GL_LINE_STIPPLE);
}

}

void drawBoundary(float length, float x, float y)
{

glBegin(GL_LINE_LOOP);
glColor3f(1.0, 1.0, 1.0);
glVertex2f(X_CENTRE - length - 20, Y_CENTRE - length);   //these 4 points 
draw the game boundary
glVertex2f(X_CENTRE - length - 20, Y_CENTRE + length);   //these 4 points 
draw the game boundary
glVertex2f(X_CENTRE + length + 20, Y_CENTRE + length);   //these 4 points 
draw the game boundary
glVertex2f(X_CENTRE + length + 20, Y_CENTRE - length);   //these 4 points 
draw the game boundary
glEnd();

glFlush();     /* execute drawing commands in buffer */

   }

/*     {



    /* display callback function called whenever contents of window need 
to be re-displayed     */
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);   /* clear window */
glLoadIdentity();

drawGrid();

drawBoundary(170, 0, 0);

glutSwapBuffers();


}


GLvoid IdleFunc(GLvoid)
{
glutPostRedisplay();
}

void myGridmenu(GLint id)
{
if (id == 1)
{
    grid = 1.0;
}
else
{
    grid = 0.0;
}
glutPostRedisplay();
}

/* graphics initialisation */
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);   /* window will be cleared to black */
}


int main(int argc, char* argv[])//standard c entry signature
{
/* window management code ... */
/* initialises GLUT and processes any command line arguments */
glutInit(&argc, argv);
/* use double-buffered window and RGBA colour model */
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
/* window width = 400 pixels, height = 400 pixels */
glutInitWindowSize(500, 500);
/* window upper left corner at (100, 100) */
glutInitWindowPosition(100, 100);
/* creates an OpenGL window and set its title bar*/
glutCreateWindow("Coursework 1");
init();

glutDisplayFunc(display);

//glutSpecialFunc(specialKeys);
//  glutSpecialUpFunc(keyGoneUp);

glutReshapeFunc(reshape);

//Create a grid that the user can turn on and off
glutCreateMenu(myGridmenu);

glutAddMenuEntry("Grid on", 1);
glutAddMenuEntry("Grid off", 2);
glutAttachMenu(GLUT_RIGHT_BUTTON);


//  SetupRC();
glutIdleFunc(IdleFunc);
glutMainLoop();

return 0;

}

The w and h取决于正交投影而不是视口。由于投影不是从 (0, 0) 开始，而是从 (-200, -200) 开始，因此您必须添加 2 个附加变量startX, startY:

int w = 1;
int h = 1;
int startX = 0;
int startY = 0;


/* reshape callback function executed when window is moved or resized */
void reshape(int width, int height)
{
    startX = -200;
    startY = -200;
    h = 400;
    w = 400;
    //set the matrix mode to PROJECTION
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0, 0, width, height);
    // use orthographic (parallel) projection
    glOrtho(-200.0, 200.0, -200.0, 200.0, -200.0, 200.0);
    //set the matrix mode to MODEL
    glMatrixMode(GL_MODELVIEW);
}

void drawGrid() {
    GLint i;

    glEnable(GL_LINE_STIPPLE); //Activates the line-style feature
    glLineStipple(1, 0xAAAA);  // Plots a dashed polyline

    glColor3f(0.8, 0.8, 0.8);

    if (grid) {
        glBegin(GL_LINES);
        for (i = 1; i <= 9; i++)
        {
            glVertex3f(startX + i * 0.1 * w, startY, 0.0);
            glVertex3f(startX + i * 0.1 * w, h - startY, 0.0);
        }

        for (i = 1; i <= 9; i++)
        {
            glVertex3f(startX, startY + i * 0.1 * h, 0.0);
            glVertex3f(w - startX, startY + i * 0.1 * h, 0.0);
        }
        glEnd();
        glDisable(GL_LINE_STIPPLE);
    }
}