   Beginners #define vertex problem
  Hi all, how are we all?I hope you guys might be able to help me out with this, I'm just starting out with direct3d programming and so I'm editing a bit of code from toymaker.info, I'm just trying to get a simple triangle showing on the screen splitting who bits of code so i have a dedicated direct3d initialisation sequence.  Starting in the main.cpp:#include <windows.h>#include "vis_setup.h"LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);// The main entry point of our Windows programint APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){// Create and fill out a window class structureWNDCLASS wcex;ZeroMemory(&wcex,sizeof(WNDCLASS));[... more windows stuff going on here]So thats the initial start up, moving on the vis_seup.h:#include <d3dx9.h>// D3DX helper functionsLPDIRECT3D9 gD3dObject=NULL;LPDIRECT3DDEVICE9 gD3dDevice=NULL;LPDIRECT3DVERTEXBUFFER9gVertexBuffer=NULL;struct TMyVertex{D3DXVECTOR3 p;// Vertex positionD3DCOLOR c;// Vertex colour};#define MYVERTEX_FVF (D3DFVF_XYZ | D3DFVF_DIFFUSE)class vis_setup{public:vis_setup(void);bool InitialiseDirect3D(HWND hWnd);bool CreateTriangle();And when i want to use MYVERTEX_FVF i do it like this:bool vis_setup::CreateTriangle(){HRESULT hr=gD3dDevice->CreateVertexBuffer(3*sizeof(TMyVertex),D3DUSAGE_WRITEONLY, MYVERTEX_FVF,D3DPOOL_MANAGED, &gVertexBuffer, NULL );if (FAILED(hr))return false;// Lock and fillTMyVertex* pVertices=NULL;This all looks alright to me but when i compile I get errors like this:Triangle fatal error LNK1169: one or more multiply defined symbols foundTriangle error LNK2005: "struct IDirect3DVertexBuffer9 * gVertexBuffer" (?gVertexBuffer@@3PAUIDirect3DVertexBuffer9@@A) already defined in main.objI dunno whats up with it, I've never being exactly confident with #defines (My c++ skills need ALOT of work) but I can't really see whats wrong with this. Anyone know?   
  First, make sure to use the source tags.You are defining a global variable: which is getting included in multiple files. One way you might get around that is, putting your variables in a class/struct.IEstruct globals{  LPDIRECT3DVERTEXBUFFER9gVertexBuffer;  globals()  { gVertexBuffer=NULL;  }};