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OpenGL trouble getting started

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So I'm giving OpenGL another shot, after approx. 1 year without touching it at all and never having got very far into it to begin with. My choice of starting point was NeHe's tutorials and the first tutorial went off without a hitch. The second lesson, however, is giving me a bit of trouble. It still compiles and runs fine, but nothing new is displayed. I added the code for drawing a triangle and a quad, but nothing shows up. I followed the tutorial exactly, so I don't know what's going on. Does anyone have any suggesstions? I'll provide code on request, but seeing as it's already on the NeHe site, it doesn't seem appropriate at this time. Thanks.

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Well, the first thing I'd do is make sure that your OpenGL application is correctly set up with Windows/WinAPI.
So basically, make sure you have a valid OpenGL rendering context.

When you know OpenGL is set up correctly, you should make sure your projection/modelview matrices are correct.

If you are using GLU, then to get correct matrices all you have to do is this:


glMatrixMode(GL_PROJECTION);
glLoadIdentity();

gluPerspective(field_of_view, screen_width / screen_height, near_plane, far_plane);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();



When you have your identity matrix loaded (or basically, the view of the world is reset), the camera is looking down the Z axis, which is <0.0, 0.0, -1.0>.
That way, you can render a basic quad with a common Z value of -10.0, and it will be visible without changing your camera orientation.


glBegin(GL_QUADS);
glVertex3f(-1.0f, -1.0f, -10.0f);
glVertex3f(1.0f, -1.0f, -10.0f);
glVertex3f(1.0f, 1.0f, -10.0f);
glVertex3f(-1.0f, 1.0f, -10.0f);
glEnd();



Here's a minimal complete application which shows a rotating quad.


#define SCREEN_WIDTH 1024
#define SCREEN_HEIGHT 768
#define BITSPERPIXEL 32
#define DEPTHBUFFER_PRES 24

#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>

HWND hWnd;
HDC hDC;
HGLRC hRC;

/****************************************************************************************

Window procedure (WinAPI)

*****************************************************************************************/

LRESULT CALLBACK WndProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK WndProc (HWND hWnd, UINT message,
WPARAM wParam, LPARAM lParam)
{

switch (message)
{
case WM_CLOSE:
PostQuitMessage (0);
return 0;

case WM_KEYDOWN:

//If ESC is pressed, close the application.
if (wParam == VK_ESCAPE)
{
PostQuitMessage(0);
return 0;
}

return 0;
default:
return DefWindowProc (hWnd, message, wParam, lParam);
}
}

int WINAPI WinMain (HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int iCmdShow)
{
/****************************************************************************************

Open up a window

*****************************************************************************************/

WNDCLASSEX wc;
PIXELFORMATDESCRIPTOR pfd;
int f = 0;

//Register window class
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_OWNDC;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor (NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH);
wc.lpszMenuName = NULL;
wc.lpszClassName = "FSWindow";
wc.hIconSm = LoadIcon(NULL, IDI_WINLOGO);
RegisterClassEx(&wc);

//Enable fullscreen
DEVMODE dmScreenSettings;
ZeroMemory (&dmScreenSettings, sizeof (DEVMODE));
dmScreenSettings.dmSize = sizeof (DEVMODE);
dmScreenSettings.dmPelsWidth = SCREEN_WIDTH;
dmScreenSettings.dmPelsHeight = SCREEN_HEIGHT;
dmScreenSettings.dmBitsPerPel = BITSPERPIXEL;
dmScreenSettings.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;
ChangeDisplaySettings(&dmScreenSettings, CDS_FULLSCREEN);
RECT windowRect = {0, 0, SCREEN_WIDTH, SCREEN_HEIGHT};
AdjustWindowRectEx (&windowRect, WS_POPUP, 0, WS_EX_APPWINDOW | WS_EX_TOPMOST);



//Open window
hWnd = CreateWindowEx(WS_EX_APPWINDOW | WS_EX_TOPMOST,
"FSWindow",
"Test window",
WS_POPUP,
0, 0,
SCREEN_WIDTH,
SCREEN_HEIGHT,
HWND_DESKTOP,
NULL,
hInstance,
NULL);

//Show the window
ShowWindow(hWnd, SW_NORMAL);






/****************************************************************************************

Create rendering context for OpenGL

*****************************************************************************************/

hDC = GetDC(hWnd);

//Setup pixelformat on the device context
memset(&pfd, 0, sizeof(pfd));

pfd.nSize = sizeof(pfd);
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW |
PFD_SUPPORT_OPENGL |
PFD_DOUBLEBUFFER;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = BITSPERPIXEL;
pfd.cDepthBits = DEPTHBUFFER_PRES;
pfd.iLayerType = PFD_MAIN_PLANE;

f = ChoosePixelFormat(hDC, &pfd);
SetPixelFormat(hDC, f, &pfd);

//Create and enable rendering context
hRC = wglCreateContext(hDC);
wglMakeCurrent(hDC, hRC);






/****************************************************************************************

Set up OpenGL

*****************************************************************************************/


// Set up matrices
float field_of_view = 45.0f;
float screen_width = SCREEN_WIDTH;
float screen_height = SCREEN_HEIGHT;
float near_plane = 1.0f;
float far_plane = 100.0f;

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(field_of_view, screen_width / screen_height, near_plane, far_plane);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();








/****************************************************************************************

Main loop

*****************************************************************************************/

bool quit = false;
float rot = 0.0f;
MSG msg;

while (quit == false)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT)
{
quit = TRUE;
}
else
{
TranslateMessage (&msg);
DispatchMessage (&msg);
}
}

//Clear backbuffer and reset camera
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();

//Rotate around Z axis
rot += 0.001f;
glRotatef(rot, 0, 0, 1);

//Draw quad
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, -10.0f);

glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, -10.0f);

glColor3f(0.0f, 0.0f, 1.0f);
glVertex3f(1.0f, 1.0f, -10.0f);

glColor3f(1.0f, 0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, -10.0f);
glEnd();

//Show what we have drawn to the screen
SwapBuffers(hDC);
}



/****************************************************************************************

Close application

*****************************************************************************************/

wglMakeCurrent(NULL, NULL);
wglDeleteContext(hRC);

ReleaseDC(hWnd, hDC);
DestroyWindow(hWnd);
ChangeDisplaySettings(NULL, 0);
UnregisterClass("FSWindow", hInstance);
}

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Thanks for the reply and the assistance. I got it working and am continuing through the lessons without too much trouble. Thanks.

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