I am working on drawing a player vehicle. I drew the first of eight images/orientations in isometric view, facing southwest. I wanted to get the scale right for each of the directions, based on the first image.
Perhaps most artists guess the proportion, or draw an appropriately sized/proportioned ellipse, or maybe even do the math (in which case I have nothing new). Anyway, I did the math for simutrans pixel art isometric, where the diagonals or 'sides' of the object are diagonal lines of slope 1/2 and -1/2. Standard drafting isometric has diagonals of 30º and -30º from horizontal, so the attached image only applies to pixel art.
To use: You start with a vehicle image facing one orientation. You project its length (T, I, or S) down to the ground, and measure it in pixels: X wide or Y tall. Then you use the proportions or formulas to convert the length to another orientation, and draw from that. It's also applicable to buildings and other features, but probably less practical.
I think it's neat that the proportions are based around sqrt(2), although I don't have a simple explanation of why it's that way. Maybe I overlooked a much simpler approach?
Anyway, hope this is useful.
I was making a color palette of the special colors (day/night) to share, when I noticed the chart on the wiki page was very messed up! The RGB values do not match the displayed color, and the displayed color doesn't match the HEX value.
What ARE the correct colors? Once I finish the palette I'll share it, but I don't want to spread incorrect info.