>>5923045How accurate are you trying to be? I notice /ic/ has a hard on for making everything perfect, in perspective, perfect anatomy, perfect lighting, perfect color, etc... In reality, unless you're into product design or classical figure painting, it's fine it it doesn't perfectly accurate in space.
If you still want to go that route, check out product design courses/teachers, anatomy courses, fine art. Stuff like that. For me personally, it get's too into theory and science when I just want to make cool concepts and visual development art.
If you just want to measure body parts and make sure they look alright, it just comes with pencil mileage. The more you draw the body, the better you'll understand proportions and perspective. I know it's a shitty draw more answer, but it really just comes down to gaining knowledge on the subject.