What do you mean with 'the 3D side clears the screen'?

It shouldn't be a problem to do this:

RenderFrame(){  pD3DXContext->Clear(D3DCLEAR_TARGET/D3DCLEAR_ZBUFFER);  // Do some 2D blitting  hr = pD3DDevice->BeginScene();  if( SUCCEEDED(hr) )  {    // Render the 3D part    pD3DDevice->EndScene();  }  // Show the whole frame  pD3DXContext->UpdateFrame( 0 );} 

(I have removed some of the error testing to make it easier to read)

Edited by - Spellbound on 4/3/00 3:12:16 AM

hiya

i guess ur problem is that u call D3DX.Clear... try not to clear the render target, just the Z Buffer... or u can can call Device7.Clear that accepts a list of dirty rectangles.

hope that helps

Paco

Just an added note, and you all may know this anyway but for anyone else''s sake: D3D docs state you should not mix 2D and 3D processing. Or better said "manually" blitting such as you do in Direct Draw with vertices and such that you do in D3D. If you want to emulate things like flat 2D backgrounds, HUDs, or whatever try doing it with D3DTLVERTEX. That will allow you to define where on the screen your quasi 3D background will be. Also other "flat" objects in 3D space are easy, check out MS''s Billboard demo in the 7.0 SDK. Its a great example.

The cost of not using 3d vertices to do your 2d stuff is a large performance penalty. The exact reason behind this is a little beyond my current expertise (perhaps someone here can enlight us more on that) but as I understand it going to 2D causes the driver/video card to have to change state/processing/whatever to accomdate the request. The resulting change causes a flush of all the data hence bad performance. I even read a suggestion going as far as recommending you make your mouse cursor a 3d object (a flat one of course).

Sieggy