DirectX problem

[SteelModule]

I´m new to DirectX 8.1 and I have a problem in windowed mode. When I use SDI type app and tris are rendered in filled mode, when I resize a window, the app works correctly. Image stretches, but correctly, same way as OpenGL does. But when I switch to wireframe, all goes wrong. Lines appear thinner or thicker, as if you stretch a bitmap. In MDI, when I use additional swap chains, this problem occurs everytime, i.e. in filled mode. I use vertex buffer initialized in OnInitialUpdate(). Antialiasing is off.

[JWood]

So you are using Direct3D DM? You should realize that lines are actually very thin polygons in Direct3D - so as to minimize the calling structures. This may be the root of the problem. This sounds like you are transforming the viewport instead of the projection matrix as a response to changing of the window size. If not, There are also hardware accelerator problem sometimes - check to see if it does the same thing on a different video card - or turn off hardware acceleration in the Windows display options.