Z-buffer is causing things not to draw

Question

I'm having some issues getting things to draw in DirectX9.

Here's my render function:

void Render(GameWorld& world)
{
    DWORD BackgroundColour = 0x00102010;    

    g_pd3dDevice -> Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, BackgroundColour, 1.0f, 0);

    // Begin rendering the scene.
    if (SUCCEEDED(g_pd3dDevice -> BeginScene()))
    {
        world.draw();

        g_pd3dDevice -> EndScene();
    }

    // Present the backbuffer to the display.
    g_pd3dDevice -> Present(NULL, NULL, NULL, NULL);
}

I'm setting up DirectX with this code:

// Create the D3D object, return failure if this can't be done.
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_D16;

// Create the D3DDevice
if (FAILED(g_pD3D -> CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
                                  D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                                  &d3dpp, &g_pd3dDevice)))
{
    return E_FAIL;
}

// Turn on the Z buffer
g_pd3dDevice -> SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);

g_pd3dDevice -> SetRenderState(D3DRS_ZFUNC, D3DCMP_LESS);
g_pd3dDevice -> SetRenderState(D3DRS_ZWRITEENABLE, TRUE);

// Start with lighting off - we can add lights later.
g_pd3dDevice -> SetRenderState(D3DRS_LIGHTING, FALSE);

// Set transparencies
g_pd3dDevice -> SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_pd3dDevice -> SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_pd3dDevice -> SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
g_pd3dDevice -> SetRenderState(D3DRS_BLENDOP, D3DBLENDOP_ADD);




// Set culling
g_pd3dDevice -> SetRenderState(D3DRS_CULLMODE,D3DCULL_CCW);

return S_OK;

As it is, this draws a BackgroundColour screen with nothing on it.

By turning the Z-buffer off [ie g_pd3dDevice -> SetRenderState(D3DRS_ZENABLE, D3DZB_FALSE);] everything is drawn in the order their "draw" functions are called. Objects drawn later obscure objects drawn earlier.

I have also tried making these changes:

g_pd3dDevice -> SetRenderState(D3DRS_ZFUNC, D3DCMP_GREATER);

and

g_pd3dDevice -> Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, BackgroundColour, 0.0f, 0);

The effect is now that objects that are drawn first obscure objects that are drawn later, regardless of their spacial positions.

The effect I want is for near objects to obscure far objects.

Can anybody shed some light on this.

Thank you.

Answer 1

Try removing these lines:

g_pd3dDevice -> SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);

g_pd3dDevice -> SetRenderState(D3DRS_ZFUNC, D3DCMP_LESS);
g_pd3dDevice -> SetRenderState(D3DRS_ZWRITEENABLE, TRUE);

The z-buffer is enabled by default, so it should work.
Make sure you transform your objects by the correct WorldViewProjection matrix.
If your objects are not rendered, check if World.draw() is called. Maybe BeginScene() fails?