drawing trough - over other polies??

here is the problem, the slope is a polygon
assembled object, the flat surface you can see
intersects into that object with the red marked
area, but how could i draw the object still there, but give the camera illusuion that it is actualy above the slope?

i cannot yaw the objects. they are billboard - like 2D sprites.

erm, ignore the green rectangle… it does nothing…


thanx, i never knew depth test is used for that

can be this switched on / off when drawing?

You can’t change arbitrary render state inside a glBegin/glEnd (or during glDrawArrays/glDraw[Range]Elements, obviously). Otherwise, everything can be changed, that’s why it’s called a state machine. There’s no distinct “init phase” or something.