D3DFVF_XYZRHW的z的作用
自学DirectX，在D3DFVF_XYZRHW的z上碰到困难。看了许多说明，z表示z-buffer的像素深度，用于裁剪用的，有效范围是0.0~1.0，超出这个范围就会被裁剪掉，但我发现我修改DirectX9的示例代码2，不管怎么改z，三角形总是能显示的，于是再查说是要设置z buffer，我设上后发现什么都不能显示了，希望能得到解释。主要的几段代码如下：
// A structure for our custom vertex type
struct CUSTOMVERTEX
{
FLOAT x, y, z, rhw; // The transformed position for the vertex
DWORD color; // The vertex color
};
// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZRHW|D3DFVF_DIFFUSE)
//-----------------------------------------
// Name: InitD3D()
// Desc: Initializes Direct3D
//-----------------------------------------
HRESULT InitD3D( HWND hWnd )
{
// Create the D3D object.
if( NULL == ( g_pD3D = Direct3DCreate9( D3D_SDK_VERSION ) ) )
return E_FAIL;
// Set up the structure used to create the D3DDevice
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory( &d3dpp, sizeof( d3dpp ) );
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
d3dpp.EnableAutoDepthStencil = TRUE;
d3dpp.AutoDepthStencilFormat = D3DFMT_D24X8;
// Create the D3DDevice
if( FAILED( g_pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp, &g_pd3dDevice ) ) )
{
return E_FAIL;
}
// Device state would normally be set here
return S_OK;
}
//-----------------------------------------
// Name: InitVB()
// Desc: Creates a vertex buffer and fills it with our Vertices. The vertex
// buffer is basically just a chuck of memory that holds Vertices. After
// creating it, we must Lock()/Unlock() it to fill it. For indices, D3D
// also uses index buffers. The special thing about vertex and index
// buffers is that they can be created in device memory, allowing some
// cards to process them in hardware, resulting in a dramatic
// performance gain.
//-----------------------------------------
HRESULT InitVB()
{
// Initialize three Vertices for rendering a triangle
CUSTOMVERTEX Vertices[] =
{
{ 150.0f, 50.0f, 1.0f, 1.0f, 0xffff0000, }, // x, y, z, rhw, color
{ 250.0f, 250.0f, 0.5f, 1.0f, 0xff00ff00, },
{ 50.0f, 250.0f, 0.5f, 1.0f, 0xff00ffff, },
};
// Create the vertex buffer. Here we are allocating enough memory
// (from the default pool) to hold all our 3 custom Vertices. We also
// specify the FVF, so the vertex buffer knows what data it contains.
if( FAILED( g_pd3dDevice->CreateVertexBuffer( 3 * sizeof( CUSTOMVERTEX ),
0, D3DFVF_CUSTOMVERTEX,
D3DPOOL_DEFAULT, &g_pVB, NULL ) ) )
{
return E_FAIL;
}
// Now we fill the vertex buffer. To do this, we need to Lock() the VB to
// gain access to the Vertices. This mechanism is required becuase vertex
// buffers may be in device memory.
VOID* pVertices;
if( FAILED( g_pVB->Lock( 0, sizeof( Vertices ), ( void** )&pVertices, 0 ) ) )
return E_FAIL;
memcpy( pVertices, Vertices, sizeof( Vertices ) );
g_pVB->Unlock();
return S_OK;
}
//-----------------------------------------
// Name: Cleanup()
// Desc: Releases all previously initialized objects
//-----------------------------------------
VOID Cleanup()
{
if( g_pVB != NULL )
g_pVB->Release();
if( g_pd3dDevice != NULL )
g_pd3dDevice->Release();
if( g_pD3D != NULL )
g_pD3D->Release();
}
//-----------------------------------------
// Name: Render()
// Desc: Draws the scene
//-----------------------------------------
VOID Render()
{
// Clear the backbuffer to a blue color
g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB( 0, 0, 255 ), 1.0f, 0 );
// Begin the scene
if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
{
// Draw the triangles in the vertex buffer. This is broken into a few
// steps. We are passing the Vertices down a "stream", so first we need
// to specify the source of that stream, which is our vertex buffer. Then
// we need to let D3D know what vertex shader to use. Full, custom vertex
// shaders are an advanced topic, but in most cases the vertex shader is
// just the FVF, so that D3D knows what type of Vertices we are dealing
// with. Finally, we call DrawPrimitive() which does the actual rendering
// of our geometry (in this case, just one triangle).
g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, D3DZB_TRUE );
g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof( CUSTOMVERTEX ) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLELIST, 0, 1 );
// End the scene
g_pd3dDevice->EndScene();
}
// Present the backbuffer contents to the display
g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
}
