I've made a custom engine that uses 2:1 isometric sprite graphics with a 3D world simulation. Each render tick, I convert each entity's world position into a screen position, and render their sprite appropriately:
While moving diagonally across the screen, the naive rendering approach (using the raw world -> screen pixel coordinates) caused some jitter. I resolved this by making sure that during diagonal movement, the sprite always gets rendered on the same pixel in the 2:1 pattern. For example, below is a diagonal line with a repeated 2:1 pattern. The first pixel in each step of the pattern is colored blue. If the sprite happened to start its diagonal movement on the first pixel in the pattern, I would continue to round its origin each frame to the closest blue pixel.
This gives me a sprite that looks like its traveling in a straight line, with no up/down jitter. It introduces a new issue though: if the entity's runspeed doesn't happen to perfectly line up with the pattern, it will sometimes move by 1 step, and sometimes move by 2:
This gives a slight jitter to the graphic, as it moves irregularly across the screen. This jitter isn't present if I choose a runspeed that moves the graphic a consistent number of steps each frame.
My question is: is there any fix for this? I've thought of smoothing out the irregular steps by moving the sprite less frequently, but it doesn't seem possible to get the runspeed, render rate, and update rate to all line up perfectly for any arbitrary runspeed. Maybe it is, though? Or maybe there's another solution?
