Conservation of Energy

In the realm of physically-based rendering, translucency and transparency act as key aspects in creating visually authentic and compelling images. Transparency refers to the property of an object that allows light to pass through it unhindered, hence making the object clear or invisible. This is commonly seen in materials such as glass, clear plastic, and water. On the other hand, translucency describes how light interacts with a semi-transparent object. Instead of passing directly through, light enters the object, travels within for some distance and then exits at a different location. Common examples of such surfaces include human skin, marble, milk, or wax, which exhibit a soft, diffused lighting effect when light rays pass through them. The technique to achieve this effect in graphics involves subsurface scattering, where incoming light is scattered beneath the object's surface, illuminated it in a way that showcases the material's internal structure.