If I want to create videos, pictures, 2D and 3D computer art, graphics or diagrams without taking pictures or videos of real life objects I should learn

Particularly would be useful if I could make images of humans exercising with different body joint angles

Something to draw 3D geometry that would look good to explain math, physics or chemistry to laypeople using 3D geometric shapes combined to form a object

3D shapes should be able to connect to other 3D shapes

Not to make 2D blueprints