Lately i've been reading many online tutorials on 3D computer science. I'm trying to understand how a 3D system works and how can i generate one without the use of a library like openGL or DirectX. So i've got a few questions to ask:

1) How can i stop bitmaps from flashing, a.k.a who can i manipulate the device buffer or the window update rate?

2)Is there another method beside BitBlt?

3)Related to the above, when using vectors with double values, after calculating the right screen position, how can i insert it in BitBlt, which accepts only integers?

These are my questions. Feel free to post your opinion and/or suggestion on this.
Thanks in advance!!!