Hi everyone It is the first time I try to make volume shadow and I have some problem with stencil. Here is the code of directx sample that I got // Set renderstates (disable z-buffering, enable stencil,and // turn on alphablending) g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, FALSE ); g_pd3dDevice->SetRenderState( D3DRS_STENCILENABLE, TRUE ); g_pd3dDevice->SetRenderState( D3DRS_ALPHABLENDENABLE, TRUE ); // set reference value g_pd3dDevice->SetRenderState( D3DRS_STENCILREF, 0x1 ); // Don't change the value of pixel g_pd3dDevice->SetRenderState( D3DRS_STENCILPASS, D3DSTENCILOP_KEEP ); // Comparision g_pd3dDevice->SetRenderState( D3DRS_STENCILFUNC, D3DCMP_LESSEQUAL ); // Draw a big, gray square g_pd3dDevice->SetFVF( cc_shadowvertex::FVF ); g_pd3dDevice->SetStreamSource( 0, g_pBigSquareVB, 0, sizeof(shadowvertex)); g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 2 ); It means that all the pixel where stencil val >= reference value (1) will be overwrite by the gray square. The problem is when I change the reference value the square allways is drawn. So it means the function to compare current pixel with reference is not work. I don't have any experience about stencil so I'm not be confidence. Or I have to put some comment to initialize stencil when I create the device? Anyone can help me ? Thanks

Thanks for your help I change the D3DPRESENT_PARAMETERS to
d3dpp.AutoDepthStencilFormat = D3DFMT_D24S8;

Now the function to compare working.

If I set this value
m_pd3dDevice->SetRenderState( D3DRS_STENCILREF, 0x1 );
m_pd3dDevice->SetRenderState( D3DRS_STENCILFUNC, D3DCMP_LESSEQUAL );
The shadowed area appear in the screen

I change it to
m_pd3dDevice->SetRenderState( D3DRS_STENCILREF, 0x0 );
All the screen is gray
m_pd3dDevice->SetRenderState( D3DRS_STENCILREF, 0x2 );
no dark area in it.

But what is the meaning of D3DFMT_D24S8?