Images On Camera

I believe that you're talking about 3D models. They are created in a 3D modeling program and presented on the screen using a 3D graphics API....typically DirectX or OpenGL.

Nonono...I'm already using directX to build a game engine. I have it so you can move around the world, lets say I want a cross hair in the middle of the screen. What do I use to get that 2d image so its always right in the middle of the camera. Do I convert to orthographic after I render 3d stuff, then render a textured quad in the middle of the screen that is always right in front of the camera....what is the exepted method here?

My orignal post was a little vauge sry about that.

umm... cockpit? HUD?

for the crosshair, the method you want to use is called masking - you use your crosshair image as a transparent mask that is centered in the middle of the screen (or where ever you want to put it). over-simplified, you would draw the 3d objects first, and then use ortho mode to set the screen(window) coordinates that the image will be at, and draw it (with blending). [google] for more info.
hope that helped, and was semi-correct.