Subsurface scattering: Real skin has a complex structure that involves multiple layers of tissue and blood vessels. This causes light to scatter and be absorbed in various ways, creating a soft, translucent appearance. Simulating this effect accurately in CGI can be difficult, especially when the light interacts with complex skin features like wrinkles and pores.
Specular highlights: Real skin reflects light in a way that creates specular highlights, which are shiny areas that appear when light hits the skin at a certain angle. These highlights give the skin a sense of depth and texture, but they can be challenging to replicate in CGI because they depend on the precise shape and material properties of the skin surface.
Skin wrinkles and pores: Human skin is covered in wrinkles, pores, and other small surface imperfections that contribute to its natural texture. Creating these details in CGI can be time-consuming and computationally expensive, as each wrinkle or pore must be individually modeled and textured.
Translucency and veins: Real skin is translucent, allowing light to pass through it and revealing underlying structures such as blood vessels. Simulating this effect in CGI requires careful modeling of the skin's optical properties and the accurate placement of subsurface features like veins.
Animation: Creating realistic skin animation adds another level of complexity. The skin must move and deform naturally in response to facial expressions, body movement, and external forces like wind or gravity. This requires sophisticated animation techniques and careful attention to detail.
Hair and fuzz: Many parts of the human body are covered in fine hairs or fuzz, which contribute to the overall texture and appearance of the skin. Simulating these features in CGI can be computationally intensive and requires specialized techniques for hair rendering.
Real-time rendering: Creating realistic-looking CGI skin is especially challenging in real-time applications such as games, where frames must be rendered quickly and efficiently. Balancing visual quality with performance requirements can be a difficult task, often leading to compromises in the level of detail and realism.