OpenGL not displaying anything? - c++

Question

My problem is that my program isn't displaying anything on screen.
This is the "main.cpp" code:
#include "paStdAfx.h"
#include "OpenGL.h"
HDC hDC = NULL;
HGLRC hRC = NULL;
HWND hwnd = NULL;
HINSTANCE hInstance = GetModuleHandle(NULL);
const wchar_t* szClassName = _T("*project name :3*");
static std::wstring Titles[] = {
_T("*project name :3* - 100% free!"),
_T("*project name :3* - 100% OpenGL!"),
_T("*project name :3* - Not cross platform!"),
_T("*project name :3* - Rawr"),
_T("*project name :3* - Entirely C++!"),
_T("*project name :3* - Woo, /r/gamedev!"),
_T("*project name :3* - Platypi, platypi everywhere."),
_T("*project name :3* - Nom nom nom"),
_T("*project name :3* - Thanks, StackExchange!"),
_T("*project name :3* - DRM Free!"),
_T("*project name :3* - <3"),
_T("*project name :3* - Minecraft is also fun!")
};
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
BOOL CreateOpenGLWindow(const wchar_t*, int, int, int);
OpenGL ogl;
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{
srand(time(NULL));
const std::wstring wtt = Titles[rand() % 11];
const wchar_t* WindowTitle = wtt.c_str();
BOOL done = FALSE;
MSG msg;
if(!CreateOpenGLWindow(WindowTitle, 800, 600, 32)){ MessageBox(NULL, _T("Could not create window :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
while(!done)
{
if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if(msg.message == WM_QUIT)
done = TRUE;
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
else
{
ogl.RenderGLScene();
SwapBuffers(hDC);
}
}
ogl.KillOpenGL(hwnd, hDC, hRC);
return 0;
}
BOOL CreateOpenGLWindow(const wchar_t* title, int width, int height, int bits)
{
WNDCLASSEX wcx = {0};
DWORD dwExStyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
DWORD dwStyle = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX;
wcx.cbSize = sizeof(WNDCLASSEX);
wcx.style = CS_OWNDC;
wcx.lpfnWndProc = WndProc;
wcx.cbClsExtra = 0;
wcx.cbWndExtra = 0;
wcx.hInstance = hInstance;
wcx.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_PROGRAMICON));
wcx.hCursor = LoadCursor(NULL, IDC_ARROW);
wcx.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);
wcx.lpszClassName = szClassName;
wcx.lpszMenuName = NULL;
wcx.hIconSm = (HICON) LoadImage(hInstance, MAKEINTRESOURCE(IDI_PROGRAMICON), IMAGE_ICON, 16, 16, 0);
if(!RegisterClassEx(&wcx)){ MessageBox(NULL, _T("Failed to register window!"), _T("Error! :("), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
if(!(hwnd = CreateWindowEx(dwExStyle, szClassName, title, dwStyle, 200, 69, width, height, NULL, NULL, hInstance, NULL))){ MessageBox(NULL, _T("Failed to create the window!"), _T("Error! :("), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
ogl.CreateOpenGLContext(hwnd, &hDC, &hRC);
ogl.PrepareOpenGLScene();
ogl.ResizeGLScene(width, height);
ShowWindow(hwnd, SW_SHOW);
SetForegroundWindow(hwnd);
SetFocus(hwnd);
return TRUE;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CREATE:
ogl.ProgramIcon(hwnd);
break;
case WM_KEYDOWN:
switch(wParam)
{
case VK_ESCAPE:
PostQuitMessage(0);
break;
}
break;
case WM_CLOSE:
PostQuitMessage(0);
break;
case WM_DESTROY:
return 0;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
and this is the "OpenGL.cpp" code:
#include "paStdAfx.h"
#include "OpenGL.h"
GLvoid OpenGL::CreateOpenGLContext(HWND hwnd, HDC* hDC, HGLRC* hRC)
{
PIXELFORMATDESCRIPTOR pfd;
HGLRC tempContext;
memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
pfd.nVersion = 1;
pfd.dwFlags = PFD_DOUBLEBUFFER | PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = 32;
pfd.cDepthBits = 32;
pfd.iLayerType = PFD_MAIN_PLANE;
*hDC = GetDC(hwnd);
int PixelFormat = ChoosePixelFormat(*hDC, &pfd);
if(PixelFormat == 0){ MessageBox(NULL, _T("Could not choose pixel format :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
if(!SetPixelFormat(*hDC, PixelFormat, &pfd)){ MessageBox(NULL, _T("Could not set pixel format :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(3); }
tempContext = wglCreateContext(*hDC);
wglMakeCurrent(*hDC, tempContext);
GLenum err = glewInit();
if(GLEW_OK != err){ MessageBox(NULL, _T("Failed to initialize GLEW! :("), _T("Warning!"), MB_OK | MB_ICONINFORMATION); }
int attribs[] = {
WGL_CONTEXT_MAJOR_VERSION_ARB, 3,
WGL_CONTEXT_MINOR_VERSION_ARB, 1,
WGL_CONTEXT_FLAGS_ARB,
WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
0
};
if(!glewIsSupported("GL_VERSION_3_1")){ MessageBox(NULL, _T("OpenGL 3.1 not supported :("), _T("Warning!"), MB_OK | MB_ICONERROR); }
if(wglewIsSupported("WGL_ARB_create_context") == 1)
{
*hRC = wglCreateContextAttribsARB(*hDC, 0, attribs);
wglMakeCurrent(NULL, NULL);
wglDeleteContext(tempContext);
wglMakeCurrent(*hDC, *hRC);
}
else{ *hRC = tempContext; }
const char* GLVersionString = (char*) glGetString(GL_VERSION);
int OpenGLVersion[2];
glGetIntegerv(GL_MAJOR_VERSION, &OpenGLVersion[0]);
glGetIntegerv(GL_MINOR_VERSION, &OpenGLVersion[1]);
}
GLvoid OpenGL::PrepareOpenGLScene(GLvoid)
{
glClearColor(0.0f, 0.6f, 1.0f, 0.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
}
GLvoid OpenGL::RenderGLScene(GLvoid)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
/* Begin OpenGL Rendering */
/* End OpenGL Rendering */
}
GLvoid OpenGL::ResizeGLScene(int w, int h)
{
float ratio = 1.0 * w / h;
if(h == 0)
h = 1;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f, ratio, 0.1f, 1000.0f);
glViewport(0, 0, w, h);
}
GLvoid OpenGL::ProgramIcon(HWND hwnd)
{
HICON hIcon, hIconSm;
hIcon = (HICON) LoadImage(NULL, _T("data/icon.ico"), IMAGE_ICON, 32, 32, LR_LOADFROMFILE);
if(hIcon)
SendMessage(hwnd, WM_SETICON, ICON_BIG, (LPARAM)hIcon);
else
MessageBox(NULL, _T("Could not load the big icon! :("), _T("Error!"), MB_OK | MB_ICONERROR);
//---------------------------------------------------------------------------------------------//
hIconSm = (HICON) LoadImage(NULL, _T("data/icon.ico"), IMAGE_ICON, 16, 16, LR_LOADFROMFILE);
if(hIconSm)
SendMessage(hwnd, WM_SETICON, ICON_SMALL, (LPARAM)hIconSm);
else
MessageBox(NULL, _T("Could not load the small icon! :("), _T("Error!"), MB_OK | MB_ICONERROR);
}
GLvoid OpenGL::KillOpenGL(HWND hwnd, HDC hDC, HGLRC hRC)
{
wglMakeCurrent(NULL, NULL);
wglDeleteContext(hRC);
ReleaseDC(hwnd, hDC);
}
All the rendering code would go inside the "RenderGLScene" function inside of OpenGL.cpp, but when I place code to render basic things like trianlges or squares on the screen nothing appears. I have tried tinkering with the "gluLookAt()" function and the "gluPerspective()" function as well because I think those might be the source of my problem. I have tried both VBO and the older method that uses glBegin()/glEnd().

Answer 1

You create a double buffered context, but I don't see you performing a buffer swap (wglSwapBuffers) after finishing the rendering. Without a buffer swap you won't see anything.

Answer 2

What does your render code look like. Remember that the camera always is placed in the origin, which means that you need to draw things at negative z coordinates.

Answer 3

If you created a core context all drawing must be done using a VAO. Check the glError() return codes to see what the glDraw*() reports back.