Stepping into the shoes of a shoe designer

Image source:https://en.wikipedia.org/wiki/
The_Red_Shoes_(1948_film)#/media

I am sure each one of us have at least 3 to 4 pairs of shoes. That's the basic minimum. (Though my 4 year old niece tells me that one needs at least a rack full of shoes like she has! :D) Basic function of shoes is to protect feet. One pair is enough to serve this purpose, but shoes that one wears while jogging cannot be worn to work. As protecting feet is not the only purpose, it has to suit your dressing too. Being well aware about the ill effects of wearing high heels shoes, just to make their legs more attractive women wear it! Style and comfort are also other 'functions' that a pair of shoes need to satisfy.
Comfort and style required for one action is different than other. This is the reason why we see a wide range of shoe types adorning shelves in retail showrooms. Basic categories are formal, informal/casual, athletic/performance shoes. Many other actions can be categorised under these basic types. Going to office, semi formal parties, attending a wedding are all occasions where one needs to wear formal shoes. Catching up a movie, outing with friends and family, leisure travel etc are informal occasions where one need not be very formal but adopt trendy look with casual footwear, which could be sneakers, loafers, slip – ons, sandals, flip-flops, clogs and so on. Athletic or sports shoes are used for various athletic activities like walking, jogging, running, gym and other specialised sports like football, basketball, badminton, tennis etc. 

Apart from this classification, shoes are also categorised as per the seasonal usage. During harsh winters boots covering not only feet but legs till knees or thighs are preferred. Open sandals or canvas shoes are comfortable for dry hot climates. Rubber shoes offer better resistance to muddy and slippery conditions due to high rainfall. Thus, climatic or weather conditions is one of the parameters for shoe design.  
The priority of style and comfort varies depending on the activity. e.g. in formal shoes, style is more important but for leisure activities comfort is utmost important, off course along with style. 

Marker Renderings By Stephen Lukes
Image source:http://conceptkicks.com/tag/marker/

Designing a shoe might look an easy task but it is quite challenging. Designers are involved in research studying the activity for which the shoe is going to be designed. They understand what role style and comfort plays in that activity by observing the users. Depending on the activity, what could be the suitable material for different parts like sole and upper is decided. Different materials like leather, canvas, other fabrics, rubber have different properties which are studied as part of research. This study helps to understand potential of the material and techniques that need to be used to manufacture the shoe. The way material gets folded to create the 3D cavity for foot, leads to many interesting details which can be wisely used as design elements. Fastening details for shoes can become part of embellishment to add up to the style of shoe. 
In case of athletic shoes, ergonomics plays an important role to enhance performance of the athlete. Ergonomics is the study of human dimensions and recommended postures. Designers step into athlete's shoes to understand their needs better. Research team is continuously working on new materials and technologies to improve performance, avoid injuries to the athlete. Innovation in materials and technologies lead to new designs, forms, textures and styles. e.g, Crocs is a design based on it's material. Memory foam used in Skechers shoe offer great comfort to the user.

Diamond Walker bespoke shoes - shoe making process
Image source:https://www.youtube.com/watch?v=FILYbLR2j2o

Lot of sketches are developed based on this research and design brief to check out different possibilities. Prototypes are made. Depending on the manufacturing facility sequence of manufacturing process is developed for each design. Some design houses believe in handcrafted workmanship, some of them have a blend of machine and craft work while in many places shoes are produced completely mechanically.
This gives us a fair idea about the complex work of a shoe designer. It is so specialised that there are designers who have been working on a specialised category of shoes throughout their career. Very few work across all different categories. It's not easy to be into shoes of a shoe designer! 

Some useful links
https://youtu.be/xJigV_vo0YA
https://youtu.be/b5Pp9wROkPo
https://youtu.be/XfrK-n-ek-E
https://youtu.be/Gt-EpA8vwgk
https://youtu.be/DdKkHhlZW0I
https://youtu.be/fE0G1L4rEJw
https://youtu.be/4J_kxwT9zX4
https://www.worldfootwear.com/news/2-high-tech-innovations-that-will-change-the-footwear-industry/2454.html