Contact Shadows (Contact Shadows) is a technical term that is extremely important in rendering and optimizing game graphics (technical art). A high-precision shadow correction technology that uses the screen's depth buffer to artificially draw ultra-small shadows between objects and the ground (such as gaps between feet or pebbles) in screen space, which tend to disappear due to insufficient resolution of the shadow map.
Real-world analogy: When a signboard is placed on the ground, apart from the rough overall shadow (Shadow Map), only the ``tiny gap where it connects to the ground'' at the bottom of the signboard is carefully tightened with a black ultra-fine pencil (concrete shadow) for a professional finishing touch.
Shadow map, which is the ultra-small boundary line where an object is physically in contact with the ground, which cannot be captured by a ``rough light camera'', by slowly drawing precise, very small shadows pixel-by-pixel based on the current screen irregularities (depth value) creates a strong sense of reality in which the model is completely ``grounded'' on the ground.
Illustration: Contact Shadows (Infographic that clearly illustrates the basic processing flow and mechanism of Contact Shadow) in Japanese notation
Detailed mechanism and operating principle
Enable "Contact Shadows" and slightly ray-marching (pixel search) the camera's depth value (Scene Depth) on the screen space to add precise shadows with a pinpoint width of 1 mm on the ground surface.