The Physics of Light: Virtual Sunlight & Ambient Occlusion

In digital interface design, shadows simulate a virtual physical environment governed by consistent optical rules:

• Virtual Light Source: By universal convention in UI systems, the primary light source is positioned above and slightly in front of the screen. Light casts downwards, making positive Y-offsets standard.
• Direct Shadow vs. Ambient Occlusion:
  1. Direct Cast Shadow: Directional shadow cast along the light angle (sharp, offset downwards).
  2. Ambient Occlusion: Soft, diffuse darkness that settles where two physical surfaces meet or sit in close proximity, independent of light angle.

Top-tier design systems layer both components together for realistic physical depth.