Circles in Perspective - Part Three

In Part One and Part Two we saw how in many typical cases ellipses (circles drawn in perspective) do not seem to comply with the rules of perspective, for example, all three of these ellipses are identical, while the perspective squares that bound them are not:

The minor axis of the ellipse does not always remain perfectly vertical, however. Take this simple drawing of a pickup truck - how should the ellipses representing its tires be oriented in perspective?

This looks wrong:

Orienting the ellipses vertically looks better, but still not right:

As suggested before, if you imagine the ellipses (or the circles they represent) as the ends of cylinders, the answer becomes clear - the minor axes of the ellipses point toward the left vanishing point.

No other perspective lines define the orientation of these ellipses - only the center line, which aligns with the ellipse's minor axes matters in terms of orienting the ellipse:

 And if we place more ellipses within these, say, to add wheel covers, they align on these same center lines:

Note how the right vanishing point is not needed at all for orienting the ellipses, even though the circular faces sit on the plane that goes back to the right vanishing point, not the left. The right vanishing point helps determine the relative sizes of the ellipses, but not their orientation:

 That about covers the basics for drawing circles in perspective.