I am working on creating a C++ program that renders OpenGL in Stereo mode. I was able to get the program working except when I switch to fullscreen. In other words stereo viewing is functional in windowed mode, but shuts off as soon as I switch over into fullscreen. Once I am in fullscreen mode the image flickers (I think because the screen switches back to 60Hz from the 120Hz used for stereo, maybe?), and my glasses turn off, but the emitter still has the light on that means it is sending a stereo signal. Can anyone see what I am missing to get fullscreen rendering working?
I am using a NVidia Quadro Driver with the NVidia Geforce 3D Vision Kit (i.e. shutter glasses with an emitter). My OS is Windows Server 2003. I am using Visual Studio .NET 2003 to develop in.
As far as the software goes I mainly combined two example programs I found on the internet. For creating a OpenGL window in a Win32 I used the “Setting Up An OpenGL Window” tutorial from NeHe’s site (http://nehe.gamedev.net/lesson.asp?index=01). For the stereo code I used Paul Bourke’s Stereo Pulsar Example (Tutorial: http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/stereographics/stereorender/, Stereo Pulsar Code: http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/stereographics/stereorender/pulsar.c).
Here is my source code:
Note: I also had to include “OpenGL32.lib GLu32.lib” in “Project properties > Linker > Command Line” for this code to compile.
Stereo_Win32.cpp
/*
* This Code Was Created By Jeff Molofee 2000
* A HUGE Thanks To Fredric Echols For Cleaning Up
* And Optimizing This Code, Making It More Flexible!
* If You've Found This Code Useful, Please Let Me Know.
* Visit My Site At nehe.gamedev.net
*/
#include <windows.h> // Header File For Windows
#include <GL\gl.h> // Header File For The OpenGL32 Library
#include <GL\glu.h> // Header File For The GLu32 Library
#include <GL\glut.h>
#include "Stereo.h"
#include "Camera.h"
Camera camera; // Camera for left and right stereo viewpoints
Stereo stereo = Stereo(&camera);
HDC hDC=NULL; // Private GDI Device Context
HGLRC hRC=NULL; // Permanent Rendering Context
HWND hWnd=NULL; // Holds Our Window Handle
HINSTANCE hInstance; // Holds The Instance Of The Application
bool keys[256]; // Array Used For The Keyboard Routine
bool active=TRUE; // Window Active Flag Set To TRUE By Default
bool fullscreen=TRUE; // Fullscreen Flag Set To Fullscreen Mode By Default
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); // Declaration For WndProc
GLvoid ReSizeGLScene(GLsizei width, GLsizei height) // Resize And Initialize The GL Window
{
if (height==0) // Prevent A Divide By Zero By
{
height=1; // Making Height Equal One
}
glViewport(0,0,width,height); // Reset The Current Viewport
camera.screenwidth = width;
camera.screenheight = height;
}
int InitGL(GLvoid) // All Setup For OpenGL Goes Here
{
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black Background
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
glDepthFunc(GL_LEQUAL); // The Type Of Depth Testing To Do
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective Calculations
return TRUE; // Initialization Went OK
}
void Render(void)
{
glPushMatrix(); // Rotation
glRotatef(45,0.0,1.0,0.0);
glColor3f(0,1,1);
glBegin(GL_TRIANGLES);
glVertex3f(30,0,0);
glVertex3f(0,30,0);
glVertex3f(-30,0,0);
glEnd();
glBegin(GL_LINES);
// Red
glColor3f(1,0,0);
glVertex3f(0,0,0);
glVertex3f(100,0,0);
// Green
glColor3f(0,1,0);
glVertex3f(0,0,0);
glVertex3f(-100,0,0);
// Blue
glColor3f(0,0,1);
glVertex3f(0,0,0);
glVertex3f(0,100,0);
// Teal
glColor3f(0,1,1);
glVertex3f(0,0,0);
glVertex3f(0,-100,0);
// Yellow?
glColor3f(1,1,0);
glVertex3f(0,0,0);
glVertex3f(0,0,100);
// White
glColor3f(1,1,1);
glVertex3f(0,0,0);
glVertex3f(0,0,-100);
glEnd();
glPopMatrix(); // Rotation
}
int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity(); // Reset The Current Modelview Matrix
// Set camera to "home position"
camera.CameraHome(1);
stereo.InitStereo();
// Render Right View
stereo.SetupView(stereo.RIGHT);
Render();
// Render Left View
stereo.SetupView(stereo.LEFT);
Render();
return TRUE; // Everything Went OK
}
GLvoid KillGLWindow(GLvoid) // Properly Kill The Window
{
if (fullscreen) // Are We In Fullscreen Mode?
{
ChangeDisplaySettings(NULL,0); // If So Switch Back To The Desktop
ShowCursor(TRUE); // Show Mouse Pointer
}
if (hRC) // Do We Have A Rendering Context?
{
if (!wglMakeCurrent(NULL,NULL)) // Are We Able To Release The DC And RC Contexts?
{
MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
if (!wglDeleteContext(hRC)) // Are We Able To Delete The RC?
{
MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
hRC=NULL; // Set RC To NULL
}
if (hDC && !ReleaseDC(hWnd,hDC)) // Are We Able To Release The DC
{
MessageBox(NULL,"Release Device Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hDC=NULL; // Set DC To NULL
}
if (hWnd && !DestroyWindow(hWnd)) // Are We Able To Destroy The Window?
{
MessageBox(NULL,"Could Not Release hWnd.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hWnd=NULL; // Set hWnd To NULL
}
if (!UnregisterClass("OpenGL",hInstance)) // Are We Able To Unregister Class
{
MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hInstance=NULL; // Set hInstance To NULL
}
}
/* This Code Creates Our OpenGL Window. Parameters Are: *
* title - Title To Appear At The Top Of The Window *
* width - Width Of The GL Window Or Fullscreen Mode *
* height - Height Of The GL Window Or Fullscreen Mode *
* bits - Number Of Bits To Use For Color (8/16/24/32) *
* fullscreenflag - Use Fullscreen Mode (TRUE) Or Windowed Mode (FALSE) */
BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
GLuint PixelFormat; // Holds The Results After Searching For A Match
WNDCLASS wc; // Windows Class Structure
DWORD dwExStyle; // Window Extended Style
DWORD dwStyle; // Window Style
RECT WindowRect; // Grabs Rectangle Upper Left / Lower Right Values
WindowRect.left=(long)0; // Set Left Value To 0
WindowRect.right=(long)width; // Set Right Value To Requested Width
WindowRect.top=(long)0; // Set Top Value To 0
WindowRect.bottom=(long)height; // Set Bottom Value To Requested Height
fullscreen=fullscreenflag; // Set The Global Fullscreen Flag
hInstance = GetModuleHandle(NULL); // Grab An Instance For Our Window
wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC; // Redraw On Size, And Own DC For Window.
wc.lpfnWndProc = (WNDPROC) WndProc; // WndProc Handles Messages
wc.cbClsExtra = 0; // No Extra Window Data
wc.cbWndExtra = 0; // No Extra Window Data
wc.hInstance = hInstance; // Set The Instance
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO); // Load The Default Icon
wc.hCursor = LoadCursor(NULL, IDC_ARROW); // Load The Arrow Pointer
wc.hbrBackground = NULL; // No Background Required For GL
wc.lpszMenuName = NULL; // We Don't Want A Menu
wc.lpszClassName = "OpenGL"; // Set The Class Name
if (!RegisterClass(&wc)) // Attempt To Register The Window Class
{
MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
if (fullscreen) // Attempt Fullscreen Mode?
{
DEVMODE dmScreenSettings; // Device Mode
memset(&dmScreenSettings,0,sizeof(dmScreenSettings)); // Makes Sure Memory's Cleared
dmScreenSettings.dmSize=sizeof(dmScreenSettings); // Size Of The Devmode Structure
dmScreenSettings.dmPelsWidth = width; // Selected Screen Width
dmScreenSettings.dmPelsHeight = height; // Selected Screen Height
dmScreenSettings.dmBitsPerPel = bits; // Selected Bits Per Pixel
dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;
// Try To Set Selected Mode And Get Results. NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.
if (ChangeDisplaySettings(&dmScreenSettings,CDS_FULLSCREEN)!=DISP_CHANGE_SUCCESSFUL)
{
// If The Mode Fails, Offer Two Options. Quit Or Use Windowed Mode.
if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By
Your Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
{
fullscreen=FALSE; // Windowed Mode Selected. Fullscreen = FALSE
}
else
{
// Pop Up A Message Box Letting User Know The Program Is Closing.
MessageBox(NULL,"Program Will Now Close.","ERROR",MB_OK|MB_ICONSTOP);
return FALSE; // Return FALSE
}
}
}
if (fullscreen) // Are We Still In Fullscreen Mode?
{
dwExStyle=WS_EX_APPWINDOW; // Window Extended Style
dwStyle=WS_POPUP; // Windows Style
ShowCursor(FALSE); // Hide Mouse Pointer
}
else
{
dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; // Window Extended Style
dwStyle=WS_OVERLAPPEDWINDOW; // Windows Style
}
AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle); // Adjust Window To True Requested Size
// Create The Window
if (!(hWnd=CreateWindowEx( dwExStyle, // Extended Style For The Window
"OpenGL", // Class Name
title, // Window Title
dwStyle | // Defined Window Style
WS_CLIPSIBLINGS | // Required Window Style
WS_CLIPCHILDREN, // Required Window Style
0, 0, // Window Position
WindowRect.right-WindowRect.left, // Calculate Window Width
WindowRect.bottom-WindowRect.top, // Calculate Window Height
NULL, // No Parent Window
NULL, // No Menu
hInstance, // Instance
NULL))) // Dont Pass Anything To WM_CREATE
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
static PIXELFORMATDESCRIPTOR pfd= // pfd Tells Windows How We Want Things To Be
{
sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor
1, // Version Number
PFD_DRAW_TO_WINDOW | // Format Must Support Window
PFD_SUPPORT_OPENGL | // Format Must Support OpenGL
PFD_DOUBLEBUFFER | // Must Support Double Buffering
PFD_STEREO, // Must Support Stereo
PFD_TYPE_RGBA, // Request An RGBA Format
bits, // Select Our Color Depth
0, 0, 0, 0, 0, 0, // Color Bits Ignored
0, // No Alpha Buffer
0, // Shift Bit Ignored
0, // No Accumulation Buffer
0, 0, 0, 0, // Accumulation Bits Ignored
16, // 16Bit Z-Buffer (Depth Buffer)
0, // No Stencil Buffer
0, // No Auxiliary Buffer
PFD_MAIN_PLANE, // Main Drawing Layer
0, // Reserved
0, 0, 0 // Layer Masks Ignored
};
if (!(hDC=GetDC(hWnd))) // Did We Get A Device Context?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) // Did Windows Find A Matching Pixel Format?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
if(!SetPixelFormat(hDC,PixelFormat,&pfd)) // Are We Able To Set The Pixel Format?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
if (!(hRC=wglCreateContext(hDC))) // Are We Able To Get A Rendering Context?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
if(!wglMakeCurrent(hDC,hRC)) // Try To Activate The Rendering Context
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
ShowWindow(hWnd,SW_SHOW); // Show The Window
SetForegroundWindow(hWnd); // Slightly Higher Priority
SetFocus(hWnd); // Sets Keyboard Focus To The Window
ReSizeGLScene(width, height); // Set Up Our Perspective GL Screen
if (!InitGL()) // Initialize Our Newly Created GL Window
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}
return TRUE; // Success
}
LRESULT CALLBACK WndProc( HWND hWnd, // Handle For This Window
UINT uMsg, // Message For This Window
WPARAM wParam, // Additional Message Information
LPARAM lParam) // Additional Message Information
{
switch (uMsg) // Check For Windows Messages
{
case WM_ACTIVATE: // Watch For Window Activate Message
{
if (!HIWORD(wParam)) // Check Minimization State
{
active=TRUE; // Program Is Active
}
else
{
active=FALSE; // Program Is No Longer Active
}
return 0; // Return To The Message Loop
}
case WM_SYSCOMMAND: // Intercept System Commands
{
switch (wParam) // Check System Calls
{
case SC_SCREENSAVE: // Screensaver Trying To Start?
case SC_MONITORPOWER: // Monitor Trying To Enter Powersave?
return 0; // Prevent From Happening
}
break; // Exit
}
case WM_CLOSE: // Did We Receive A Close Message?
{
PostQuitMessage(0); // Send A Quit Message
return 0; // Jump Back
}
case WM_KEYDOWN: // Is A Key Being Held Down?
{
keys[wParam] = TRUE; // If So, Mark It As TRUE
return 0; // Jump Back
}
case WM_KEYUP: // Has A Key Been Released?
{
keys[wParam] = FALSE; // If So, Mark It As FALSE
return 0; // Jump Back
}
case WM_SIZE: // Resize The OpenGL Window
{
ReSizeGLScene(LOWORD(lParam),HIWORD(lParam)); // LoWord=Width, HiWord=Height
return 0; // Jump Back
}
}
// Pass All Unhandled Messages To DefWindowProc
return DefWindowProc(hWnd,uMsg,wParam,lParam);
}
int WINAPI WinMain( HINSTANCE hInstance, // Instance
HINSTANCE hPrevInstance, // Previous Instance
LPSTR lpCmdLine, // Command Line Parameters
int nCmdShow) // Window Show State
{
MSG msg; // Windows Message Structure
BOOL done=FALSE; // Bool Variable To Exit Loop
// Ask The User Which Screen Mode They Prefer
if (MessageBox(NULL,"Would You Like To Run In Fullscreen Mode?", "Start FullScreen?",MB_YESNO|MB_ICONQUESTION)==IDNO)
{
fullscreen=FALSE; // Windowed Mode
}
// Create Our OpenGL Window
if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen))
{
return 0; // Quit If Window Was Not Created
}
while(!done) // Loop That Runs While done=FALSE
{
if (PeekMessage(&msg,NULL,0,0,PM_REMOVE)) // Is There A Message Waiting?
{
if (msg.message==WM_QUIT) // Have We Received A Quit Message?
{
done=TRUE; // If So done=TRUE
}
else // If Not, Deal With Window Messages
{
TranslateMessage(&msg); // Translate The Message
DispatchMessage(&msg); // Dispatch The Message
}
}
else // If There Are No Messages
{
// Draw The Scene. Watch For ESC Key And Quit Messages From DrawGLScene()
if (active) // Program Active?
{
if (keys[VK_ESCAPE]) // Was ESC Pressed?
{
done=TRUE; // ESC Signalled A Quit
}
else // Not Time To Quit, Update Screen
{
DrawGLScene(); // Draw The Scene
SwapBuffers(hDC); // Swap Buffers (Double Buffering)
}
}
if (keys[VK_F1]) // Is F1 Being Pressed?
{
keys[VK_F1]=FALSE; // If So Make Key FALSE
KillGLWindow(); // Kill Our Current Window
fullscreen=!fullscreen; // Toggle Fullscreen / Windowed Mode
// Recreate Our OpenGL Window
if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen))
{
return 0; // Quit If Window Was Not Created
}
}
}
}
// Shutdown
KillGLWindow(); // Kill The Window
return (msg.wParam); // Exit The Program
}
Stereo.h
#include "Point3d.h"
#include "Camera.h"
class Stereo
{
public:
Stereo(Camera *camera);
~Stereo(void);
void InitStereo(void);
void SetupView(int side);
public:
Camera *camera;
Point3d r;
double ratio,radians,wd2,ndfl;
double left,right,top,bottom,near_plane,far_plane;
enum {
RIGHT = 0,
LEFT = 1
};
};
Stereo.cpp
#include <math.h>
#include <gl/glut.h> // Header File For Glut Operations
#include "Stereo.h"
#include "Point3d.h"
#include "Camera.h"
#define DTOR 0.0174532925 // Degrees to Radians
#define CROSSPROD(p1,p2,p3) \
p3.x = p1.y*p2.z - p1.z*p2.y; \
p3.y = p1.z*p2.x - p1.x*p2.z; \
p3.z = p1.x*p2.y - p1.y*p2.x
Stereo::Stereo(Camera *_camera)
{
camera = _camera;
}
Stereo::~Stereo(void)
{
}
void Stereo::InitStereo() {
near_plane = 0.1;
far_plane = 10000;
// Clip to avoid extreme stereo
near_plane = camera->focallength / 5;
ratio = camera->screenwidth / (double)camera->screenheight;
radians = DTOR * camera->aperture / 2; // aperature = 50 degrees
wd2 = near_plane * tan(radians);
ndfl = near_plane / camera->focallength;
// Derive the two eye positions
CROSSPROD(camera->vd,camera->vu,r);
Normalise(&r);
r.x *= camera->eyesep / 2.0;
r.y *= camera->eyesep / 2.0;
r.z *= camera->eyesep / 2.0;
}
void Stereo::SetupView(int side)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if(side == RIGHT)
{
// Set the Right viewing frustrum
left = - ratio * wd2 - 0.5 * camera->eyesep * ndfl;
right = ratio * wd2 - 0.5 * camera->eyesep * ndfl;
}
else if (side == LEFT)
{
// Set the Left Viewing Frustrum
left = - ratio * wd2 + 0.5 * camera->eyesep * ndfl;
right = ratio * wd2 + 0.5 * camera->eyesep * ndfl;
}
top = wd2;
bottom = - wd2;
glFrustum(left,right,bottom,top,near_plane,far_plane);
glMatrixMode(GL_MODELVIEW);
if(side == RIGHT)
{
// Set to Right Buffer
glDrawBuffer(GL_BACK_RIGHT);
}
else if (side == LEFT)
{
// Set to Left Buffer
glDrawBuffer(GL_BACK_LEFT);
}
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
if(side == RIGHT)
{
// Set where right camera is looking
gluLookAt(camera->vp.x + r.x,
camera->vp.y + r.y,
camera->vp.z + r.z,
camera->vp.x + r.x + camera->vd.x,
camera->vp.y + r.y + camera->vd.y,
camera->vp.z + r.z + camera->vd.z,
camera->vu.x,
camera->vu.y,
camera->vu.z);
}
else if (side == LEFT)
{
// Set where left camera is looking
gluLookAt(camera->vp.x - r.x,
camera->vp.y - r.y,
camera->vp.z - r.z,
camera->vp.x - r.x + camera->vd.x,
camera->vp.y - r.y + camera->vd.y,
camera->vp.z - r.z + camera->vd.z,
camera->vu.x,
camera->vu.y,
camera->vu.z);
}
}
Camera.h
#pragma once
#include "Point3d.h"
class Camera
{
public:
Camera();
Camera(Point3d,Point3d,Point3d,double,double,double,int,int);
~Camera(void);
void CameraHome(int mode);
public:
Point3d vp; /* View position */
Point3d vd; /* View direction vector */
Point3d vu; /* View up direction */
double focallength; /* Focal Length along vd */
double aperture; /* Camera aperture */
double eyesep; /* Eye separation */
int screenwidth,screenheight;
};
Camera.cpp
#include "camera.h"
Camera::Camera() {}
Camera::Camera(Point3d _vp, Point3d _vd, Point3d _vu, double _focallength, double _aperture, double _eyesep, int _screenwidth, int _screenheight)
{
vp = _vp;
vd = _vd;
vu = _vu;
focallength = _focallength;
aperture = _aperture;
eyesep = _eyesep;
screenwidth = _screenwidth;
screenheight = _screenheight;
}
Camera::~Camera(void){}
/*
Move the camera to the home position
*/
void Camera::CameraHome(int mode)
{
aperture = 50;
focallength = 70;
eyesep = focallength / 20;
if(mode == 0)
{
// Camera position
vp = Point3d(0,0,focallength);
// Camera view direction
vd = Point3d(0,0,-1);
}
else if (mode == 1)
{
/* Special camera position so the beam crosses the view */
// Camera position
vp = Point3d(39,53,22);
// Camera view direction
vd = Point3d(-vp.x, -vp.y, -vp.z);
}
// Up vector
vu = Point3d(0,1,0);
}
Point3d.h
#pragma once
class Point3d
{
public:
Point3d(void);
Point3d(double,double,double);
~Point3d(void);
void SetPointLocation(double,double,double);
public:
double x,y,z;
};
void Normalise(Point3d *p);
Point3d.cpp
#include "Point3d.h"
#include <math.h>
Point3d::Point3d(void)
{
Point3d(0.0,0.0,0.0);
}
Point3d::Point3d(double _x, double _y, double _z)
{
x = _x;
y = _y;
z = _z;
}
Point3d::~Point3d(void){}
void Point3d::SetPointLocation(double _x, double _y, double _z)
{
x = _x;
y = _y;
z = _z;
}
void Normalise(Point3d *p)
{
double length;
length = sqrt(p->x * p->x + p->y * p->y + p->z * p->z);
if (length != 0) {
p->x /= length;
p->y /= length;
p->z /= length;
} else {
p->x = 0;
p->y = 0;
p->z = 0;
}
}