I'm fairly new to openGL and have written a simple 2d program to draw some connected wide lines. One part of the program draws to 2 end to end lines of width 10. I find that the lines are rendered differently on 2 different computers...on one there is a small gap between the lines since the line ends are not capped and the lines are not parallel. On another computer, the gap does not appear. Both computers are running Windows XP with the same openGL version, so I assume the graphics card is affecting the way the lines are capped (or not, as the case may be). Further, on one computer, I cannot seem to render lines with a line width > 10.
My question is simply how can I render connected lines without gaps regardless of the computer's graphics card and also how can I render lines wider than 10 such that they are always displayed with the width that I specify?
Also, are there other issues I should be aware of that may affect the rendering of a 2D scene due to different graphics card implementations?