homemade engine issues

//  6/7/06//  Andrew Monshizadeh//  OpenGL 3d engine using glut#include <GL/glut.h>#include <cmath>#include <iostream>#include <stdlib.h>#include <stdio.h>#include <string.h>using namespace std;// window global variablesint WINDOW_WIDTH = 800;int WINDOW_HEIGHT = 600;int windowids[1];  // can be used to store multiple window ids in case there are multiple windowschar title[13] = "test engine";// call back functions to be usedvoid initializecallbacks();void displaycallback();void keyboardcallback(unsigned char key, int x, int y);void passivemotioncallback(int x, int y);void reshapecallback(int w, int h);void timercallback(int time);// setup visual requirmentsvoid initializevisuals();// variables used for movementconst float piover180 = 0.0174532925f;  // pi / 180, for degree to radian transformfloat heading; // direction character is facingfloat xpos; // x-axis position of the playerfloat zpos; // z-axis position of the playerfloat ypos = 0.5; // y-axis position of the playerGLfloat	yrot; // y-axis rotationGLfloat lookupdown = 0.0f; // value to look up or downGLfloat	z=0.0f;				// Depth Into The Screenint mousebasex = WINDOW_WIDTH/2;int mousebasey = WINDOW_HEIGHT/2;int main(int argc, char* argv[]){  glutInit(&argc, argv);  initializevisuals();  initializecallbacks();    glutMainLoop();    return 0;}//----------------------------------------------------------------------------////                              call back section                             ////----------------------------------------------------------------------------//void initializecallbacks(){  // setting up the call back functions  glutDisplayFunc(displaycallback);  // display call back  glutKeyboardFunc(keyboardcallback);  //  keyboard call back  glutPassiveMotionFunc(passivemotioncallback);  // passive mouse motion call back  glutReshapeFunc(reshapecallback); // screen reshape call back  glutTimerFunc(15, timercallback, 0);  // timer call back}void keyboardcallback(unsigned char key, int x, int y){  switch (key)  {    // miscellaneous input    case 27: // 'esc'      exit(0); // end the program      break;        // movement input    case 'a':      xpos -= (float)sin(heading*piover180 + 90.0f*piover180) * 0.05f;      zpos -= (float)cos(heading*piover180 + 90.0f*piover180) * 0.05f;			break;		case 'd':      xpos += (float)sin(heading*piover180 + 90.0f*piover180) * 0.05f;      zpos += (float)cos(heading*piover180 + 90.0f*piover180) * 0.05f;      break;    case 'w':      xpos -= (float)sin(heading*piover180) * 0.05f;			zpos -= (float)cos(heading*piover180) * 0.05f;			break;		case 's':      xpos += (float)sin(heading*piover180) * 0.05f;      zpos += (float)cos(heading*piover180) * 0.05f;  }    int dims[4];  glGetIntegerv(GL_VIEWPORT, dims);    int dx = x - mousebasex;  int dy = y - mousebasey;  mousebasex = x;  mousebasey = y;  //  if (x < 20)//  {//    glutWarpPointer(dims[2]/2, y);//    mousebasex = dims[2]/2;//  }//  if (x > (dims[2]/2 - 20))//  {//    glutWarpPointer(dims[2]/2, y);//    mousebasex = dims[2]/2;//  }    lookupdown += dy * 0.5f;  heading -= dx * 0.5f;  if(heading < 0.0f)    heading = heading + 360.0f;  else if(heading > 360.0f)    heading = heading - 360.0f;  yrot = heading;}void passivemotioncallback(int x, int y){  int dims[4];  glGetIntegerv(GL_VIEWPORT, dims);    int dx = x - mousebasex;  int dy = y - mousebasey;  mousebasex = x;  mousebasey = y;    if (x < 20)  {    glutWarpPointer(dims[2]/2, y);    mousebasex = dims[2]/2;  }  if (x > (dims[2] - 20))  {    glutWarpPointer(dims[2]/2, y);    mousebasex = dims[2]/2;  }    lookupdown += dy * 0.5f;  heading -= dx * 0.5f;  if(heading < 0.0f)    heading = heading + 360.0f;  else if (heading > 360.0f)    heading = heading - 360.0f;  yrot = heading;}void reshapecallback(int w, int h){  glViewport(0, 0, w, h);  	glMatrixMode(GL_PROJECTION);						// Select The Projection Matrix	glLoadIdentity();									// Reset The Projection Matrix	// Calculate The Aspect Ratio Of The Window	gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f);	glMatrixMode(GL_MODELVIEW);							// Select The Modelview Matrix	glLoadIdentity();									// Reset The Modelview Matrix}void timercallback(int time){  glutPostRedisplay();  glutTimerFunc(10, timercallback, 0);}void displaycallback(){  int dims[4];  glGetIntegerv(GL_VIEWPORT, dims);   	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear The Screen And The Depth Buffer  glMatrixMode(GL_MODELVIEW);  glLoadIdentity();									// Reset The View	GLfloat xtrans = -xpos;	GLfloat ztrans = -zpos;	GLfloat ytrans = 0; // -walkbias-0.25f;	GLfloat sceneroty = 360.0f - yrot;	  glRotatef(lookupdown,1.0f,0,0);	glRotatef(sceneroty,0,1.0f,0);	glTranslatef(xtrans, ytrans, ztrans);		glBegin(GL_QUADS);		glColor3f(0.0f,1.0f,0.0f);			// Set The Color To Green		glVertex3f( 0.5f, 0.5f,-0.5f);			// Top Right Of The Quad (Top)		glVertex3f(-0.5f, 0.5f,-0.5f);			// Top Left Of The Quad (Top)		glVertex3f(-0.5f, 0.5f, 0.5f);			// Bottom Left Of The Quad (Top)		glVertex3f( 0.5f, 0.5f, 0.5f);			// Bottom Right Of The Quad (Top)				glColor3f(1.0f,0.5f,0.0f);			// Set The Color To Orange		glVertex3f( 0.5f,-0.5f, 0.5f);			// Top Right Of The Quad (Bottom)		glVertex3f(-0.5f,-0.5f, 0.5f);			// Top Left Of The Quad (Bottom)		glVertex3f(-0.5f,-0.5f,-0.5f);			// Bottom Left Of The Quad (Bottom)		glVertex3f( 0.5f,-0.5f,-0.5f);			// Bottom Right Of The Quad (Bottom)				glColor3f(1.0f,0.0f,0.0f);			// Set The Color To Red		glVertex3f( 0.5f, 0.5f, 0.5f);			// Top Right Of The Quad (Front)		glVertex3f(-0.5f, 0.5f, 0.5f);			// Top Left Of The Quad (Front)		glVertex3f(-0.5f,-0.5f, 0.5f);			// Bottom Left Of The Quad (Front)		glVertex3f( 0.5f,-0.5f, 0.5f);			// Bottom Right Of The Quad (Front)				glColor3f(1.0f,1.0f,0.0f);			// Set The Color To Yellow		glVertex3f( 0.5f,-0.5f,-0.5f);			// Bottom Left Of The Quad (Back)		glVertex3f(-0.5f,-0.5f,-0.5f);			// Bottom Right Of The Quad (Back)		glVertex3f(-0.5f, 0.5f,-0.5f);			// Top Right Of The Quad (Back)		glVertex3f( 0.5f, 0.5f,-0.5f);			// Top Left Of The Quad (Back)				glColor3f(0.0f,0.0f,1.0f);			// Set The Color To Blue		glVertex3f(-0.5f, 0.5f, 0.5f);			// Top Right Of The Quad (Left)		glVertex3f(-0.5f, 0.5f,-0.5f);			// Top Left Of The Quad (Left)		glVertex3f(-0.5f,-0.5f,-0.5f);			// Bottom Left Of The Quad (Left)		glVertex3f(-0.5f,-0.5f, 0.5f);			// Bottom Right Of The Quad (Left)				glColor3f(1.0f,0.0f,1.0f);			// Set The Color To Violet		glVertex3f( 0.5f, 0.5f,-0.5f);			// Top Right Of The Quad (Right)		glVertex3f( 0.5f, 0.5f, 0.5f);			// Top Left Of The Quad (Right)		glVertex3f( 0.5f,-0.5f, 0.5f);			// Bottom Left Of The Quad (Right)		glVertex3f( 0.5f,-0.5f,-0.5f);			// Bottom Right Of The Quad (Right)	glEnd();						// Done Drawing The Quad		glFlush();	glutSwapBuffers();}void initializevisuals(){  // creating the window and drawing buffers    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH); // create double buffer and z-depth buffer  glutInitWindowSize(WINDOW_WIDTH, WINDOW_HEIGHT); // create window using predetermined window sizes  glutInitWindowPosition(0,0);  windowids[0]=glutCreateWindow(title);  glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // set background color to white	glClearDepth(1.0); // enables clearing of the depth buffer  glEnable(GL_DEPTH_TEST); // enable depth testing	glDepthFunc(GL_LESS);	// the type of depth test to do	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// really nice perspective calculations, got from NeHe tutorial 10  int dims[4];  glGetIntegerv(GL_VIEWPORT, dims);	glMatrixMode(GL_PROJECTION);						// Select The Projection Matrix	glLoadIdentity();									// Reset The Projection Matrix	// Calculate The Aspect Ratio Of The Window	gluPerspective(45.0f,(GLfloat)dims[2]/(GLfloat)dims[3],0.1f,100.0f);	glMatrixMode(GL_MODELVIEW);							// Select The Modelview Matrix	glLoadIdentity();									// Reset The Modelview Matrix}