Glbegin (gl_quads) не рисует воздушный змей ⇐ C++

[Anonymous]

Я пытаюсь нарисовать кайт:

...using glbegin (gl_quads)

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Код: Выделить всё

// g++ main.cpp -lopengl32 -lgdi32 -municode
#include 
#include 
#include   //system
#include    //printf, puts

void RenderQuad(HDC DeviceContext){
GLdouble A[] = {0, -1};
GLdouble B[] = {-1, 1};
GLdouble C[] = {1, 1};
GLdouble O[] = {0, 0};
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);

//Render kite
glBegin(GL_QUADS);
glVertex2dv(A);
glVertex2dv(B);
glVertex2dv(O);
glVertex2dv(C);
glEnd();

//Check For Errors
for (bool ErrorOccured; ;){
switch(glGetError()){
#define OTG_CASE(C) case C: puts("ERROR: "#C); ErrorOccured = true; break;
case GL_NO_ERROR:
if (ErrorOccured){
puts("Failed To Render Quad");
return;
}
goto noerrors;
OTG_CASE(GL_INVALID_ENUM)
OTG_CASE(GL_INVALID_VALUE)
OTG_CASE(GL_INVALID_OPERATION)
OTG_CASE(GL_STACK_OVERFLOW)
OTG_CASE(GL_STACK_UNDERFLOW)
OTG_CASE(GL_OUT_OF_MEMORY)
default: puts("ERROR: Unknown"); ErrorOccured = true; break;
#undef OTG_CASE
}
}
noerrors:
//Swap Buffers
if (!SwapBuffers(DeviceContext)){
printf("Failed To Swap Buffers %lu", GetLastError());
return;
}

system("PAUSE");
}

int wWinMain(HINSTANCE Instance, HINSTANCE, PWSTR, int CmdShow){
HWND Window;
HDC DeviceContext;
HGLRC RenderingContext;
WNDCLASSW WindowClass = {0};

//Register Window Class
WindowClass.lpfnWndProc = DefWindowProcW;
WindowClass.hInstance = Instance;
WindowClass.lpszClassName = L"OTG";
{
ATOM WindowClassAtom;
WindowClassAtom = RegisterClassW(&WindowClass);
if (!WindowClassAtom){
printf("Failed To Register Class %lu", GetLastError());
return -1;
}
SetLastError(NO_ERROR);
}

//Create Window
Window = CreateWindowExW(
0,
WindowClass.lpszClassName,
L"firstwindow",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
Instance,
NULL
);
if (!Window){
printf("Failed To Create Window %lu", GetLastError());
goto unregisterclass;
}
SetLastError(NO_ERROR);

ShowWindow(Window,  CmdShow);

//Get Device Context
DeviceContext = GetDC(Window);
if (!DeviceContext){
printf("Failed To Retrieve Device Context %lu", GetLastError());
goto destroywindow;
}
SetLastError(NO_ERROR);

{
//Find A Suitable Pixel Format, Manually
PIXELFORMATDESCRIPTOR PixelFormatDescriptor = {0};
int PixelFormat;
PixelFormat = 1;
for (;;++PixelFormat){
int NumPixelFormats;
printf("Checking Pixel Format %d\n", PixelFormat);
NumPixelFormats = DescribePixelFormat(
DeviceContext,
PixelFormat,
sizeof(PixelFormatDescriptor),
&PixelFormatDescriptor
);
if (!NumPixelFormats){
printf("Failed To Describe PixelFormat %lu", GetLastError());
goto releasedevicecontext;
}
SetLastError(NO_ERROR);
if (
PixelFormatDescriptor.dwFlags & PFD_SUPPORT_OPENGL
&& PixelFormatDescriptor.dwFlags & PFD_DOUBLEBUFFER
&& PixelFormatDescriptor.cDepthBits >  1
)
break;
if (PixelFormat == NumPixelFormats){
puts("All Formats Checked - Cannot Find A Suitable OpenGL Pixel Format");
goto releasedevicecontext;
}
}
puts("Format Is Suitable");

//Set Pixel Format
if (!SetPixelFormat(DeviceContext, PixelFormat, &PixelFormatDescriptor)){
printf("Failed To Set Pixel Format %lu", GetLastError());
goto releasedevicecontext;
}
SetLastError(NO_ERROR);
}

//Create OpenGl Rendering Context
RenderingContext = wglCreateContext(DeviceContext);
if (!RenderingContext){
printf("Failed To Create OpenGL Rendering Context %lu", GetLastError());
goto releasedevicecontext;
}
SetLastError(NO_ERROR);

//Make OpenGl Rendering Context Current
if (!wglMakeCurrent(DeviceContext, RenderingContext)){
printf("Failed To Make OpenGL Rending Context Current %lu", GetLastError());
goto deleterenderingcontext;
}
puts("Initialized OpenGL Rendering Context");

RenderQuad(DeviceContext);

//Make OpenGl Rendering Context Not Current
if(!wglMakeCurrent(NULL, NULL))
printf("\nFailed To Make OpenGL Rendering Context Not Current %lu", GetLastError());

deleterenderingcontext:
SetLastError(NO_ERROR);
if (!wglDeleteContext(RenderingContext))
printf("\nFailed To Delete OpenGL Rendering Context %lu", GetLastError());

releasedevicecontext:
SetLastError(NO_ERROR);
if (!ReleaseDC(Window, DeviceContext))
printf("\nFailed To Release Device Context %lu", GetLastError());

destroywindow:
SetLastError(NO_ERROR);
if (!DestroyWindow(Window))
printf("\nFailed To Destroy Window %lu", GetLastError());

unregisterclass:
SetLastError(NO_ERROR);
if (!UnregisterClassW(WindowClass.lpszClassName, Instance))
printf("\nFailed To Unregister Class %lu", GetLastError());
return 0;
}

... Однако, он продолжает рисовать треугольник:

Почему рендель Как работает glbegin (gl_quads) ? Как я могу исправить renderquad так, чтобы он производил ожидаемый выход?

Подробнее здесь: https://stackoverflow.com/questions/796 ... ing-a-kite