drawing polygons and delete them

hi everyone… i need a huge help!!
i’m doing a game for univ and i must find out a way to draw polygons and delete them so i can see the part of a texture that i have like background.
my whole texture at the beginning is cover, for example with a black square.
then i draw a polygon (any kind of polygon!!!)
and i should see the part of the texture that is under the area of my polygon and so on till to discover complitely the texture…
i don’t know how to do this…i created a matrix where i put “1” to define the area of my polygon but don’t kow how to go on…
pls help me!!

Are you in the same class as this guy?

You need to read up on alpha values and blending, google should give you a pretty nice load of websites with information about this.