Problem with texture mapping

I am new in this forum but i little know and work with opengl.
My question is , in order to do texture mapping we actually try to fit the image in a square box. But if the image is not entirely covered with the box for example if the image is a plane and it is concave , when i try to fit the image in a box many area will remain with the background color (as the object of the image is concave) which is not at all required in my aero fighter game . Because in my game the background color changes with every stage i enter.

So, what should i do so that the empty area of the image should not show but only the object of the image will show??

Plz help me…

You mean : make the background part transparent ?
You have to add an alpha channel to your textures : 0 in for the background, 255 for the plane.

Sorry i can not explain it properly.
Plz Look at the picture below

(1,0)       (1,1)
| _/  \_   |
| |    |   |
| |____|   |

The square will be the box and the image of the house i want to add. I don’t want to show the outside of the house(image)(vacent area enclosed by square). What should i do for this?

You should add transparent values out of the house image. Image formats like jpg and bmp don’t support transparency, you can try with tga or png.

thanks. I will try.

plz give me some suggestions to do it or any link so that i can do it.