accumulation buffer and bitmaps

Hi. I’ve read various posts and articles about using the accumulation buffer, but am still having some trouble. I’m wondering if there is anything I need especially to do when trying to use the accumulation buffer while rendering into a bitmap.

When rendering to a window, our software uses the accumulation buffer to do some antialiasing. I’ve recently added a version rendering to a bitmap, and the accumulation buffer is not working in that case.

I’ve set the pixel format accumulation buffer bits to 32 when setting up the bitmap, and when I ask OpenGL for the bits per pixel, I get 8 in each color. glGetError() after each call to glAccum() returns 0. If I set the scale value passed to glAccum() to 0 for each call, I still get a final picture (non-antialiased) in my bitmap. So it seems that the GL_RETURN isn’t going to my bitmap, and I don’t know whether anything is actually going to the accumulation buffer.

After the glAccum() I do a BitBlt to a window instead of the swap buffers I’d do if I were rendering directly to the window. As I said, I’m definitely getting my picture into the bitmap originally, but I can’t tell that the calls to glAccum() are having any effect.

I’m working on a Windows 2000 system. Any idea what might be going on here?