Hey, i'm following the basics of directx programming and i'm at a point where i'm learning how to create and draw a triangle to the screen.
My code works good, but there's just one thing i don't understand. I'll show you some code first. This is basically how i create my triangle:
I've created my custom vertex
PDIRECT3DVERTEXBUFFER9 g_pVB = NULL; // Buffer to hold vertices
// A structure for our custom vertex type
struct CUSTOMVERTEX
{
FLOAT x, y, z; // The untransformed, 3D position for the vertex
DWORD color; // The vertex color
};
// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE)
Then i create the triangle like so:
HRESULT PVCore::pvCreateTriangle ( )
{
// Initialize three vertices for rendering a triangle
CUSTOMVERTEX g_Vertices[] =
{
{ -1.0f,-1.0f, 0.0f, 0xffff0000, },
{ 1.0f,-1.0f, 0.0f, 0xff0000ff, },
{ 0.0f, 1.0f, 0.0f, 0xffffffff, },
};
// Create the vertex buffer.
if( FAILED( g_pd3dDevice->CreateVertexBuffer( 3 * sizeof( CUSTOMVERTEX ),
0, D3DFVF_CUSTOMVERTEX,
D3DPOOL_DEFAULT, &g_pVB, NULL ) ) )
{
return E_FAIL;
}
// Fill the vertex buffer.
VOID* pVertices;
if( FAILED( g_pVB->Lock( 0, sizeof( g_Vertices ), ( void** )&pVertices, 0 ) ) )
return E_FAIL;
memcpy( pVertices, g_Vertices, sizeof( g_Vertices ) );
g_pVB->Unlock();
return S_OK;
}
And in the renderloop:
g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof( CUSTOMVERTEX ) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 1 );
Now so far, when i run my code i see a triangle. But i don't get is this part:
CUSTOMVERTEX g_Vertices[] =
{
{ -1.0f,-1.0f, 0.0f, 0xffff0000, },
{ 1.0f,-1.0f, 0.0f, 0xff0000ff, },
{ 0.0f, 1.0f, 0.0f, 0xffffffff, },
};
Why am i working with 1 and 0 ? How come i'm not using the actual X,Y coordinates of my window?? My window is 640x480. But when i change it to this:
CUSTOMVERTEX g_Vertices[] =
{
{ 320.0f, 25.0f, 0.0f, 0xffff0000, },
{ 600.0f, 400.0f, 0.0f, 0xff0000ff, },
{ 40.0f, 400.0f, 0.0f, 0xffffffff, },
};
Then i don't see a triangle. So my question really is, how come? And how can i still use the X,Y pixel location instead of using -1.0 to 1.0??
