Why am I not seeing a red triangle on my blue screen?



#pragma comment(linker, "/subsystem:windows")

#include <windows.h>
#pragma comment (lib, "openGL32")
#include <gl/gl.h>
#include <gl/glu.h>


HDC g_HDC;
bool fullScreen = true;

void Render()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode( GL_MODELVIEW );
glLoadIdentity();


glColor4f(1.0f, 0.0f, 0.0f, 0.0f);

glPushMatrix();
glLoadIdentity();

glBegin(GL_POLYGON);

float zPos = -10.0f;

glVertex3f(100.0f, 100.0f, zPos);
glVertex3f(200.0f, 200.0f, zPos);
glVertex3f(300.0f, 100.0f, zPos);

glEnd();
glPopMatrix();

glFlush();

// Bring back buffer to foreground
SwapBuffers(g_HDC);
}

void SetupPixelFormat(HDC hDC)
{
int nPixelFormat;

static PIXELFORMATDESCRIPTOR pfd = {
sizeof(PIXELFORMATDESCRIPTOR), //size of structure
1, //default version
PFD_DRAW_TO_WINDOW | //window drawing support
PFD_SUPPORT_OPENGL | //opengl support
PFD_DOUBLEBUFFER, //double buffering support
PFD_TYPE_RGBA, //RGBA color mode
32, //32 bit color mode
0, 0, 0, 0, 0, 0, //ignore color bits
0, //no alpha buffer
0, //ignore shift bit
0, //no accumulation buffer
0, 0, 0, 0, //ignore accumulation bits
16, //16 bit z-buffer size
0, //no stencil buffer
0, //no aux buffer
PFD_MAIN_PLANE, //main drawing plane
0, //reserved
0, 0, 0 }; //layer masks ignored

nPixelFormat = ChoosePixelFormat(hDC, &pfd);

SetPixelFormat(hDC, nPixelFormat, &pfd);
}

void InitOpenGL()
{

GLint iViewport[4];
glGetIntegerv( GL_VIEWPORT, iViewport );
glViewport(0, 0, iViewport[2], iViewport[3]);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho( iViewport[0], iViewport[0]+iViewport[2], iViewport[1], iViewport[1]+iViewport[3], -100.0f, 100.0f );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glEnable(GL_DEPTH_TEST);
glFrontFace(GL_CW);
//glPolygonMode(GL_FRONT, GL_FILL);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glDisable(GL_CULL_FACE);

glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
//glEnable(GL_BLEND);

glClearColor(0.0f, 0.0f, 1.0f, 0.0f);
}

/* Windows Event Procedure Handler */
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
// Rendering and Device Context variables are declared here.
static HGLRC hRC;
static HDC hDC;

// Width and Height for the window our robot is to be displayed in.
int width, height;

switch(message)
{
case WM_CREATE: //window being created
{
hDC = GetDC(hwnd); //get current windows device context
g_HDC = hDC;

SetupPixelFormat(hDC); //call our pixel format setup function

// Create rendering context and make it current
hRC = wglCreateContext(hDC);
wglMakeCurrent(hDC, hRC);

InitOpenGL();

return 0;
break;
}
case WM_CLOSE: //window is closing
{
/* Deselect rendering context and delete it*/
wglMakeCurrent(hDC, NULL);
wglDeleteContext(hRC);

/* Send quit message to queue*/
PostQuitMessage(0);

return 0;
break;
}
case WM_SIZE:
{
/* Retrieve width and height*/
height = HIWORD(lParam);
width = LOWORD(lParam);

/* Don't want a divide by 0*/
if (height == 0)
height = 1;

/* Reset the viewport to new dimensions*/
glViewport(0, 0, width, height);

/* Set current Matrix to projection and load in the orthographic matrix*/
//glMatrixMode(GL_PROJECTION);
//glLoadIdentity(); //reset projection matrix
//glOrtho(...

//glMatrixMode(GL_MODELVIEW); //set modelview matrix
//glLoadIdentity(); //reset modelview matrix

return 0;
break;
}
default:
{
break;
}
}

return (DefWindowProc(hwnd, message, wParam, lParam));
}

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
// Getting rid of unused variable warnings.
(nCmdShow);
(lpCmdLine);
(hPrevInstance);

WNDCLASSEX windowClass; //window class
HWND hwnd; //window handle
MSG msg = MSG(); //message
bool done; //flag for completion of app
DWORD dwExStyle; //window extended style
DWORD dwStyle; //window style
RECT windowRect;

/* Screen/display attributes*/
int width = 2880;
int height = 1800;
int bits = 32;

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

/* Fill out the window class structure*/
windowClass.cbSize = sizeof(WNDCLASSEX);
windowClass.style = CS_HREDRAW | CS_VREDRAW;
windowClass.lpfnWndProc = WndProc;
windowClass.cbClsExtra = 0;
windowClass.cbWndExtra = 0;
windowClass.hInstance = hInstance;
windowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
windowClass.hCursor = LoadCursor(NULL, IDC_ARROW);
windowClass.hbrBackground = NULL;
windowClass.lpszMenuName = NULL;
windowClass.lpszClassName = "MyClass";
windowClass.hIconSm = LoadIcon(NULL, IDI_WINLOGO);

/* Register window class*/
if (!RegisterClassEx(&windowClass))
return 0;

/* Check if fullscreen is on*/
if (fullScreen)
{
DEVMODE dmScreenSettings;
memset(&dmScreenSettings, 0, sizeof(dmScreenSettings));
dmScreenSettings.dmSize = sizeof(dmScreenSettings);
dmScreenSettings.dmPelsWidth = width; //screen width
dmScreenSettings.dmPelsHeight = height; //screen height
dmScreenSettings.dmBitsPerPel = bits; //bits per pixel
dmScreenSettings.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;

if( ChangeDisplaySettings(&dmScreenSettings, CDS_FULLSCREEN != DISP_CHANGE_SUCCESSFUL) )
{
/* Setting display mode failed, switch to windowed*/
MessageBox(NULL, "Display mode failed", NULL, MB_OK);
fullScreen = false;
}
}

/* Check if fullscreen is still on*/
if (fullScreen)
{
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);

/* Class registerd, so now create our window*/
hwnd = CreateWindowEx(NULL, "MyClass", //class name
"2D_Project", //app name
dwStyle |
WS_CLIPCHILDREN |
WS_CLIPSIBLINGS,
0, 0, //x and y coords
windowRect.right - windowRect.left,
windowRect.bottom - windowRect.top, //width, height
NULL, //handle to parent
NULL, //handle to menu
hInstance, //application instance
NULL); //no xtra params

/* Check if window creation failed (hwnd = null ?)*/
if (!hwnd)
return 0;

ShowWindow(hwnd, SW_SHOW); //display window
UpdateWindow(hwnd); //update window

done = false; //initialize loop condition variable

/* Main message loop*/
while (!done)
{
PeekMessage(&msg, hwnd, NULL, NULL, PM_REMOVE);

if (msg.message == WM_QUIT) //did we receive a quit message?
{
done = true;
}
else
{
Render();
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}

if (fullScreen)
{
ChangeDisplaySettings(NULL, 0);
ShowCursor(TRUE);
}

return msg.wParam;
}

Well... what exactly are you seeing at the moment? Also, use the code tags to format your post for code.

Check this line :

glColor4f(1.0f, 0.0f, 0.0f, 0.0f);

How can you see anything when your alpha component is 0? Set it to 1 for opaque.

I tried using <code></code>, but that didn't seem to do the trick. I can't seem to find the tags you're referring to. If you'll show me, I'll be more than happy to add the tags.

I thought the alpha channel was the other way around? Higher value for higher transparency. I haven't enabled GL_BLEND, so that shouldn't be an issue anyway, correct? I tried it with a 1, and I've verified glDisable(GL_BLEND) doesn't help either.

The only thing I see right now is a blue screen (the clear color). On occasion I can see red, but its not what I expect it to be in terms of size, then I keep messing around with code/values and lose it again... I feel like my ortho setup or camera knowledge is lacking somewher....

I compiled and ran your program, this is what I get:

http://imgur.com/bYRSX

Looks right to me?

WHAAAAT? That's really frustrating. I wonder if it has something to do with my machine. I'll try it on another one. I'm currently trying it on a dual booted macbook pro retina. Maybe apple's drivers aren't up to par or something...?

Your screenshot gave me an idea.

Ok, I tried using

glVertex3f(0.0f, 200.0f, zPos);
glVertex3f(1600.0f, 900.0f, zPos);
glVertex3f(2800.0f, 200.0f, zPos);

because I have a 2800x1600 display. That way I had a better chance of seeing the triangle, since it would be larger, and I would expect to see the tip of the top be at my center screen, and bottom edges meet properly near the bottom edge of the screen. What I actually see (I'd post a screenshot if I knew the capture button...) is that the triangle tip is appearing roughly in the bottom right quadrant of my screen. Somewhere I must be getting bad values for screen size/viewport size/resolution/whatever.

Also of note is that the thumbnail image of the program on my taskbar appears to be correct (maybe slightly off, but certainly different than what the fullscreen image is showing... A fullscreen issue then?

The triangle appears where I'd expect it on my computer based on your projection matrix, vertex data and the screen resolution I am running. Try setting your projection matrix to identity (i.e. comment out the gOrtho line in InitOpenGL) and change your polygon draw calls to the following:

glVertex3f(-1.0f, -1.0f, 0);
glVertex3f(1.0f, -1.0f, 0);
glVertex3f(0.0f, 1.0f, 0);

You should see a big red triangle covering the entire screen (regardless of resolution) like this:

http://imgur.com/THV9H

Doing that, I get a triangle with top at center screen, and bottom corners on the bottom of the screen at 1/4 and 3/4 screen width. The thumbnail image appears to have the triangle positioned such that the bottom left corner is at the bottom left of the image (as if at 0,0), top at (1/3 width, 2/3 height), and the bottom right corner at (2/3 width, 0). I'm still attempting to get this going on another machine too.....