The "slew rate" is the max speed that the output voltage can change at. In my case it was 13 volts per microsecond, which is slower than I wanted but much faster than any original vector games.

On my console I also wanted to display text and sprites, in addition to vector lines, so I needed the speed to be as high as possible. But this means drawing a line is a lot harder. The algorithm to get straight lines is called Bressenham's line algorithm (there are some examples on wikipedia).

Using Bressenham with a vector console is totally stupid, but the whole thing was silly anyway.

What you could do is intentionally slow down the slew rate by adding a low-pass filter.

Actually looking at your image again, if that's how a triangle ends up, I might be talking about the wrong thing. If the micro is running at a few MHz, then the steppiness of the shape is due to the clock speed of the GPIO or however data is sent to the DAC.

My method was drawing shapes slowly, moving small amounts with bressenham and delaying at each position, whereas if you want to go round as fast as possible, maybe it would be better to build a latch circuit to ensure both X and Y update at the same time. Or, it might be enough to just slow down the slew rate and slow down the output of the microcontroller, then the relative time between X and Y updating would be negligible.

I dunno. What kind of DAC are you using?