   blending problem
  hi,i don't know why but i can't make the blending correct:glEnable(GL_BLEND);glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);and i'm testing with two overlapped polygons with two different colors:glColor4f(0,1,0,0.5);glColor4f(1,0,0,0.5);but all i can see is the black background. it seems that my QT4 programdoesn't support the alpha channel or the alpha channel is only one bit insize.i don't know if i miss anything, i've already set the qt glwidghtformat to support alpha and the alphabuffer size to 8.please help.thank you.   