Hi! I was watching a video in the anatomy course about simplifying joints in perspective. Marshall Vandruff mentioned briefly that drawing a sphere with cross contours in perspective takes several hours to master. How do you draw a sphere correctly in the way that Marshall describes? I don't believe I am doing it correctly, it doesn't look as "3D" as his. Is it just a matter of getting clean ellipses or are there perspective rules regarding how the contours should be aligned? I did the 250 box challenge from DrawABox, and I know from that there are ways to check if your box is approximately in the right perspective. Is there a similar way to check the contour lines?

How does Marshall know how much the humerus will foreshorten at a certain angle? Is it just a matter of knowing intuitively from drawing so much?

Hi! This may be a dumb question, but how do you draw a sphere correctly in the way that Marshall describes? He said it takes several hours of work to do it right. I don't believe I am doing it correctly, it doesn't look as "3D" as his. Is it just a matter of getting clean ellipses or are there perspective rules regarding how the contours should be aligned? I did the 250 box challenge from DrawABox, and I know from that there are ways to check if your box is approximately in the right perspective. Is there a similar way to check the contour lines?