DrawPrimitive Function {D3D}??

I dont understand the third parameter in this function..
The prototype of the function is this:

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HRESULT DrawPrimitive(
  [in]  D3DPRIMITIVETYPE PrimitiveType,
  [in]  UINT StartVertex,
  [in]  UINT PrimitiveCount
);

In my program I have 2 primatives I want to draw so my understanding is that that parameter would be 2...but my program only works if it is set to 5.
d3ddev->DrawPrimitive(D3DPT_TRIANGLESTRIP,0,5);


I am trying to get these 3 other verts drawn to the screen but it will only draw the 1 triangle? How can I get 2 triangles on the screen?

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#include <windows.h>
#include <windowsx.h>
#include <d3d9.h>

#define  SCREEN_WIDTH 800
#define  SCREEN_HEIGHT 600

LPDIRECT3D9 d3d;
LPDIRECT3DDEVICE9 d3ddev;
LPDIRECT3DVERTEXBUFFER9 v_buffer = NULL; // the pointer to the v buffer

void initD3D(HWND);
void render_frame(void);
void cleanD3D(void);
void init_graphics(void);

#define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)
typedef struct CUSTOMVERTEXT{
	FLOAT X,Y,Z,RHW; 
	DWORD COLOR;
}CUSTOMVERTEXT;

LRESULT CALLBACK winProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE pevInstance, LPSTR lpCmdLine,
					int cmdShow)
{
	HWND hwnd;
	WNDCLASSEX wc;
	ZeroMemory(&wc, sizeof(WNDCLASSEX));

	wc.cbSize = sizeof(WNDCLASSEX);
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc = winProc;
	wc.hInstance = hInstance;
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
	//wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
	wc.lpszClassName = L"WindowClass";

	RegisterClassEx(&wc);

	hwnd = CreateWindowEx(NULL,
						L"WindowClass",
						L"Our First D3D Program",
						WS_OVERLAPPEDWINDOW,
						0,0,
						SCREEN_WIDTH,SCREEN_HEIGHT,
						NULL,
						NULL,
						hInstance,
						NULL);

	ShowWindow(hwnd, cmdShow);
	// init D3D
	initD3D(hwnd);
	// enter main loop
	MSG msg;
	while (TRUE)
	{
		while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}

		if(msg.message == WM_QUIT)
			break;

		render_frame();

	}

	// clean up DirectX and COM
	cleanD3D();
	return msg.wParam;
}

LRESULT CALLBACK winProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	
	switch (message)
	{
	
	case WM_DESTROY:
		
			PostQuitMessage(0);
			return 0;
		
	}
	return DefWindowProc(hwnd,message,wParam,lParam);
}

void initD3D(HWND hwnd)
{
	d3d = Direct3DCreate9(D3D_SDK_VERSION); // create the d3d interface
	D3DPRESENT_PARAMETERS d3dpp; // create a struct to old device info
	ZeroMemory(&d3dpp, sizeof(d3dpp)); // clear out struct
	d3dpp.Windowed = TRUE;
	d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD; // discard old frames
	d3dpp.hDeviceWindow = hwnd; // set window to be used by d3d
	d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8; 
	d3dpp.BackBufferWidth = SCREEN_WIDTH;
	d3dpp.BackBufferHeight = SCREEN_HEIGHT;
	// create the device

	d3d->CreateDevice(D3DADAPTER_DEFAULT,
					D3DDEVTYPE_HAL,
					hwnd,
					D3DCREATE_SOFTWARE_VERTEXPROCESSING,
					&d3dpp,
					&d3ddev);
}

void render_frame()
{

	// clear the window to a deep blue
	d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 40, 100), 1.0f, 0);
	d3ddev->BeginScene();
	
	d3ddev->SetFVF(CUSTOMFVF);
	d3ddev->SetStreamSource(0,v_buffer,0,sizeof(CUSTOMVERTEXT));
	d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST,0,1);
	d3ddev->EndScene();
	d3ddev->Present(NULL,NULL,NULL,NULL);
	init_graphics();
}
void cleanD3D(void)
{
	v_buffer->Release();
	d3ddev->Release();
	d3d->Release();
}

void init_graphics(void) // check the comas if program doesnt run
{
	//create the vertices using the custom vertext struct
	
	CUSTOMVERTEXT vertices[] = {
		{0, 0, 0.5f, 1.0f, D3DCOLOR_XRGB(0,0,255)},
		{300, 600, 0.5f, 1.0f, D3DCOLOR_XRGB(0,255,0)},
		{0, 600, 0.5f, 1.0f, D3DCOLOR_XRGB(255,0,0)},

		{ 320.0f, 50.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255) },
		{ 520.0f, 400.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 255, 0) },
		{ 120.0f, 400.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0) }
	
	};
	//create the vertext buffer
	d3ddev->CreateVertexBuffer(6*sizeof(CUSTOMVERTEXT),
								0,
								CUSTOMFVF,
								D3DPOOL_MANAGED,
								&v_buffer,
								NULL);
	VOID* pVoid; // void pointer
	// lock vert buffer and load verts into 
	v_buffer->Lock(0,0,(void**)&pVoid,0);
	memcpy(pVoid,vertices,sizeof(vertices));
	v_buffer->Unlock();
}
Last edited on
cmon anybody?
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