// #pragma comment (lib,"glut32.lib")

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <GL/glut.h>
float lx=0.0f,lz=-1.0f;
float x=0.0f,z=5.0f;

float angle = 0.0f;


void change(int w, int h)
{
    float ratio = w * 1.0 / h;
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0, 0, w, h);
    gluPerspective(45.0f, ratio, 0.1f, 100.0f);
    glMatrixMode(GL_MODELVIEW);
}

void draw(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    gluLookAt( x, 1.0f, z,
            x+lx, 1.0f, z+lz,
            0.0f, 1.0f, 0.0f);

    // Draw ground
    glColor3f(0.9f, 0.9f, 0.9f);
    glBegin(GL_QUADS);
    glVertex3f(-10.0f, 0.0f, -10.0f);
    glVertex3f(-10.0f, 0.0f, 10.0f);
    glVertex3f( 10.0f, 0.0f, 10.0f);
    glVertex3f( 10.0f, 0.0f, -10.0f);
    glEnd();

    glutSwapBuffers();
}

void processNormalKeys(unsigned char key, int x, int y)
{

    if (key == 27)
        exit(0);
}

void processSpecialKeys(int key, int xx, int yy)
{

    float fraction = 0.1f;

    switch (key) {
        case GLUT_KEY_LEFT :
            angle -= 0.01f;
            lx = sin(angle);
            lz = -cos(angle);
            break;
        case GLUT_KEY_RIGHT :
            angle += 0.01f;
            lx = sin(angle);
            lz = -cos(angle);
            break;
        case GLUT_KEY_UP :
            x += lx * fraction;
            z += lz * fraction;
            break;
        case GLUT_KEY_DOWN :
            x -= lx * fraction;
            z -= lz * fraction;
            break;
    }
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(320,320);
    glutCreateWindow("Lighthouse3D - GLUT Tutorial");
    glutDisplayFunc(draw);
    glutReshapeFunc(change);
    glutIdleFunc(draw);
    glutKeyboardFunc(processNormalKeys);
    glutSpecialFunc(processSpecialKeys);
    glEnable(GL_DEPTH_TEST);
    glutMainLoop();

    return 1;
}