Plz, teach me how to draw a grid!

[Messiah]

Hi, everyone
I'm a student from Thailand named "Boss" (This is really my nickname)
Now, I studying C++ and I got some problem.

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

// Global variables
HWND    hWnd;
HDC     hDC;
HGLRC   hRC;

// Set up pixel format for graphics initialization
void SetupPixelFormat()
{
    PIXELFORMATDESCRIPTOR pfd, *ppfd;
    int pixelformat; 

    ppfd = &pfd;

    ppfd->nSize = sizeof(PIXELFORMATDESCRIPTOR);
    ppfd->nVersion = 1;
    ppfd->dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    ppfd->dwLayerMask = PFD_MAIN_PLANE;
    ppfd->iPixelType = PFD_TYPE_COLORINDEX;
    ppfd->cColorBits = 16;
    ppfd->cDepthBits = 16;
    ppfd->cAccumBits = 0;
    ppfd->cStencilBits = 0;

    pixelformat = ChoosePixelFormat(hDC, ppfd);
    SetPixelFormat(hDC, pixelformat, ppfd);
}

// Initialize OpenGL graphics
void InitGraphics()
{
    hDC = GetDC(hWnd);

    SetupPixelFormat();

    hRC = wglCreateContext(hDC);
    wglMakeCurrent(hDC, hRC);

    glClearColor(0, 0, 0, 0.5);
    glClearDepth(1.0);
    glEnable(GL_DEPTH_TEST);
}

// Resize graphics to fit window
void ResizeGraphics()
{
    // Get new window size
    RECT rect;
	int width, height;
	GLfloat aspect;

    GetClientRect(hWnd, &rect);
    width = rect.right;
    height = rect.bottom;
    aspect = (GLfloat)width / height;

    // Adjust graphics to window size
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0, aspect, 1.0, 100.0);
    glMatrixMode(GL_MODELVIEW);
}

// Draw frame
void DrawGraphics()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

	

    // Show the new scene
    glFlush();
    SwapBuffers(hDC);
}

// Handle window events and messages
LONG WINAPI MainWndProc (HWND hWnd, UINT uMsg, WPARAM  wParam, LPARAM  lParam)
{
    switch (uMsg)
    {
    case WM_SIZE:
        ResizeGraphics();
        break;

    case WM_CLOSE: 
        DestroyWindow(hWnd);
        break;
 
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
 
    // Default event handler
    default: 
        return DefWindowProc (hWnd, uMsg, wParam, lParam); 
        break; 
    } 
 
    return 1; 
}

// Main function
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{

    const LPCWSTR appname = TEXT("OpenGL Sample");

    WNDCLASS wndclass;
    MSG      msg;
 
    // Define the window class
    wndclass.style         = 0;
    wndclass.lpfnWndProc   = (WNDPROC)MainWndProc;
    wndclass.cbClsExtra    = 0;
    wndclass.cbWndExtra    = 0;
    wndclass.hInstance     = hInstance;
    wndclass.hIcon         = LoadIcon(hInstance, appname);
    wndclass.hCursor       = LoadCursor(NULL,IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wndclass.lpszMenuName  = appname;
    wndclass.lpszClassName = appname;
 
    // Register the window class
    if (!RegisterClass(&wndclass)) return FALSE;
 
    // Create the window
    hWnd = CreateWindow(
            appname,
            appname,
            WS_OVERLAPPEDWINDOW | WS_CLIPSIBLINGS | WS_CLIPCHILDREN,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            800,
            600,
            NULL,
            NULL,
            hInstance,
            NULL);
 
    if (!hWnd) return FALSE;

    // Initialize OpenGL
    InitGraphics();

    // Display the window
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    // Event loop
    while (1)
    {
        if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE) == TRUE)
        {
            if (!GetMessage(&msg, NULL, 0, 0)) return TRUE;

            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        DrawGraphics();
    }

    wglDeleteContext(hRC);
    ReleaseDC(hWnd, hDC);
}

This is the main code that i must use to draw the grid My teacher told me to use for to loop the grid.
I tried so hard but it's still not work.

the grid must look like chest board. I'm very confuse now, Plz help me T^T


Ps. I must write some code in the function "DrawGraphics" and use GL_LINES or something like this

[Salem]

Edited for correct code tags

[bernt]

I tried so hard but it's still not work.

// Draw frame
void DrawGraphics()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

	

    // Show the new scene
    glFlush();
    SwapBuffers(hDC);
}

There's nothing there.
What have you tried?

[Messiah]

sry i forgot
i tried it in many way, first i tried it with the line and tried to make it loop

void DrawGraphics()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glColor3f(1.0f,1.0f,1.0f);

for(i=2.0f;i<=-5.0f;i--)
{
glBegin(GL_LINES);
{
glVertex3f(3.0f,i,-7.0f);
glVertex3f(-3.0f,i,-7.0f);
}
}

// Show the new scene
glFlush();
SwapBuffers(hDC);
}

it's still not work T^T it's only black screen but when I bring "for" out, the line appear

[MK27]

for(i=2.0f;i<=-5.0f;i--)
{
glBegin(GL_LINES);
{
glVertex3f(3.0f,i,-7.0f);
glVertex3f(-3.0f,i,-7.0f);
}
}

Why are those brackets there? That is not how glBegin() works (notice, it is a statement of it's own). You should call glBegin() before the loop, do the vertex drawing in the loop, and then call glEnd(). Most GL commands should not appear between Begin() and End(), including glFlush() and (I'm sure) whatever SwapBuffers does. So you do need to call it, most appropriately right after that loop.

I'd really recommend you just use something as simple as possible until you get the GL stuff to work, otherwise you are just asking for headaches. Then add stuff in a bit at a time, always checking to see that it renders the way you want.

[Salem]

0 / 2 posts on using code tags - this isn't a good sign...