Inability to draw on certain pixels

Hi, I am using opengl to draw to a bitmap using VC++ in a CWND. I have set my view using orthogonal projection w/ parameters set to the size of the bitmap. I have noticed some inconsistancies when plotting lines similar to that of an audio signal. I have tested the plotting by drawing a vertical line from the bottom of the window to the top of the window for every pixel on the screen. The problem I have is that at about 3 quarters of the width of the screen whether I am using single or dual monitors, there are several vertical lines that don’t get plotted. Blank lines range from 3 to over 12 and don’t seem to be in any pattern. They are not continuous either. I am extremely stumped on why the drawing has been flawless except in this one small region with a width of about 30 pixels. I Any advice on this is appreciated

I had the same problem in orthogonal projection. But the problem only showed up on a Voodoo 3 graphics card, several different Geforce cards all rendered graphics acurately. I never found a solution or explanation. Since then I’ve been working with a normal projection matrix and haven’t noticed any discrepencies.

It is possible that I’m just not seeing it though, a triangle can be rendered across one of these gaps but a vertice cannot appear on these random lines.

You could have some rounding artifacts going on. If you’re drawing pixel-perfect lines, make sure you’re not drawing with integer values, but with floats set to the middle of each pixel. Remember that in OpenGL, integer values are between pixels.

Instead of glVertex2i(x, y) try glVertex2f(x + 0.5f, y + 0.5f).

Aside from that, no idea. Can you post an obligatory screenshot, just in case it jogs someone’s memory?