if you have already used blender you know that all there is opengl... from snout to tail. now they've got the same effect there like you know from file selection dialogs: a rectangle with alternating dots that invert what is behind. i wanna do a similar selection rectangle for my map editor. i can do stippled lines that have the dot-nodot look but i can't figure out how i can make that line invert the color on the screen. somebody has an idea?

thx for the tip it worked. the BlendFunc is not involved though. the following did the trick:

glEnable( GL_COLOR_LOGIC_OP );glLogicOp( GL_INVERT );