如何在OpenGL中输出变量数

我正在用OpenGL编写一款游戏，其中有3个大盒子和1个小盒子。小盒子藏在其中一个大盒子下面，用户必须按A、B或C键才能显示小盒子的位置。我想要追踪用户猜了多少次，玩了多少回合等等，但我不完全确定如何在OpenGL中输出增量数字。我想在每次发生与数字相关的事情时增加数字，但我就是不知道怎么做。有人能给我指个正确的方向吗?非常感谢!

main.cpp:

#include "Box.h"
#include "Font.h"
#include "Camera.h"
#include "Time.h"
#include <vector>
using namespace std;
#include "vgl.h"
using namespace glm;
#define SPACEBAR_KEY 32
#define ESCAPE_KEY 033
vector<Box * > boxes;
Camera* camera;
Font* font;
int numGenerator, guesses, totalGuesses, rounds, averageGuesses;
bool win;
void closeApp()
{
    delete camera;
    delete font;

    for (auto it = boxes.begin(); it != boxes.end(); ++it)
        delete (*it);

}
void startNewGame()
{
    rounds++;
    win = false;
    guesses = 0;
    numGenerator = rand() % 3;
    boxes[1]->Visible = true;
    boxes[2]->Visible = true;
    boxes[3]->Visible = true;
    if (numGenerator == 0)
    {
        boxes[0]->Position = vec3(0.0f, -3.0f, 0.0f);
    }
    else if (numGenerator == 1)
    {
        boxes[0]->Position = vec3(0.0f, 0.0f, 0.0f);
    }
    else
    {
        boxes[0]->Position = vec3(0.0f, 3.0f, 0.0f);
    }
}
void keyboard(unsigned char key, int x, int y)
{
    switch (key) 
    {
        case ESCAPE_KEY:  // ASCII Escape Key Code
            closeApp();
            exit(EXIT_SUCCESS);
            break;
        case 'a':
            boxes[1]->Visible = false;
            if (boxes[0]->Position != vec3(0.0f, -3.0f, 0.0f))
            {
                guesses++;
                totalGuesses++;
            }
            else
            {
                win = true;
            }
            glutPostRedisplay();
            break;
        case 'b':
            boxes[2]->Visible = false;
            if (boxes[0]->Position != vec3(0.0f, 0.0f, 0.0f))
            {
                guesses++;
                totalGuesses++;
            }
            else
            {
                win = true;
            }
            glutPostRedisplay();
            break;
        case 'c':
            boxes[3]->Visible = false;
            if (boxes[0]->Position != vec3(0.0f, 3.0f, 0.0f))
            {
                guesses++;
                totalGuesses++;
            }
            else
            {
                win = true;
            }
            glutPostRedisplay();
            break;
        case 'r':
            startNewGame();
            glutPostRedisplay();
            break;
    }
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    font->printText("Guessing Game!", 260, 500, 20);
    font->printText("Press 1, 2, or 3 to make one of the boxes disappear!", 10, 480, 15);
    font->printText("Try to find the small cube! Press 'r' to restart!", 30, 460, 15);
    if (win)
    {
        font->printText("You win!", 20, 200, 30);
    }
    font->printText("Guesses: ", 20, 350, 15);
    font->printText("Rounds played: ", 20, 330, 15);
    font->printText("Total guesses: ", 20, 310, 15);
    font->printText("Average guesses: ", 20, 290, 15);

    boxes[0]->Draw(camera->ProjectionMatrix, camera->ViewMatrix);
    boxes[1]->Draw(camera->ProjectionMatrix, camera->ViewMatrix);
    boxes[2]->Draw(camera->ProjectionMatrix, camera->ViewMatrix);
    boxes[3]->Draw(camera->ProjectionMatrix, camera->ViewMatrix);

    glutSwapBuffers();
}
void init()
{
    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glEnable(GL_CULL_FACE);
    srand(time(NULL));
    font = new Font();
    camera = new Camera();
    camera->ViewMatrix = glm::lookAt(glm::vec3(0, 0, 20), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));

    VertexBufferData vertexBufferData = VertexBufferData("Data\Models\Objects.xml");
    boxes.push_back(new Box(vertexBufferData, glm::vec3(0.0f, 0.0f, 0.0f), "data/images/wood.bmp", "Data\Shaders\Vertex.shader", "Data\Shaders\Fragment.shader", vec3(0.4f, 0.4f, 0.4f), true));
    boxes.push_back(new Box(vertexBufferData, glm::vec3(0.0f, -3.0f, 0.0f), "data/images/ground.tga", "Data\Shaders\Vertex.shader", "Data\Shaders\Fragment.shader", vec3(1.0f, 1.0f, 1.0f), true));
    boxes.push_back(new Box(vertexBufferData,glm::vec3(0.0f, 0.0f, 0.0f), "data/images/metal.bmp", "Data\Shaders\Vertex.shader", "Data\Shaders\Fragment.shader", vec3(1.0f, 1.0f, 1.0f), true));
    boxes.push_back(new Box(vertexBufferData, glm::vec3(0.0f, 3.0f, 0.0f), "data/images/brick.bmp", "Data\Shaders\Vertex.shader", "Data\Shaders\Fragment.shader", vec3(1.0f, 1.0f, 1.0f), true));
    startNewGame();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH);
    glutInitWindowSize(1024, 768);
    glutInitContextProfile(GLUT_CORE_PROFILE);
    glutCreateWindow("Satterwhite_Project_5");

    if (glewInit())
    {
        cerr << "Unable to init glew" << endl;
        exit(EXIT_FAILURE);
    }
    init();
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboard);
    glutMainLoop();
    return 0;
}