I tried to draw a simple quad from (-3,-4) to (0,0) using the commands below:
and i got the output in the left picture.The blue pixel is the origin.The yellow pixels are the pixels where i expected the quad boundary to be.And the red pixels are the actual output.What i cant get is if i want the upper left corner of the quad at(-3,-4) why is it ending up at (-3,-3)?
Also the bottom is not at the origin.there is a problem with the y-direction here
Then i tried positive numbers as:
Now i get the output at the right.Now there is a problem with the x-direction !!
Is there some convention regarding the drawing of quads in opengl ? That the boundary pixels will not be drawn?