Comment 27 for bug 164233

> http://jhcloos.com/PostScript/XYZsweep.pdf 404[s]

D’Oh. I thought that I had pushed that out ages ago. It is there now.
As is the .ps version on which it is based.

Using the demos, the spacing is evident in the gtk demo (cairo master,
here) and in the qt4 demo when using Arthur with anti-aliased graphics.
Switching to splash or disabling graphics anti-aliasing avoids the spacing.

The rendering remains blocky, though. Only per-pixel sampling of the
shading would solve that issue.

On the cairo side, using cairo’s gradient api probably would help.