Multiplicative Blend (Multiplicative blend / Multiplicative composition / Blend DstColor Zero) is a technical term that is extremely important in rendering and optimization of game graphics (technical art). A basic explanation of how to darken the background, such as shadows, stained glass, scorch marks, and muddy puddles, using a mode that combines the new pixel color and the already drawn background color by "multiplying (A x B)" in translucent drawing.
Real-world analogy: Color composition by layering colored "thin translucent colored cellophane (multiply)" on top of a beautiful photo (background) and dyeing the whole thing moistly and darkly while retaining 100% of the photo's pattern
Multiplicative blend is "a light subtraction (filter) system that 'multiplies' (x)'s the already drawn background color by a new color". Multiplying color values (0.0 to 1.0) by 1.0 (pure white) does not change the value at all (becomes completely transparent), so the white background is completely ignored. On the other hand, if you multiply by 0.5 (gray) or 0.0 (pure black), the original background color will darken evenly. This allows you to fully utilize the rugged feel of the bricks on the ground, while perfectly blending the beautiful natural "shadows", "scorch", and "dirt" onto it so that they blend in smoothly.
Illustration: Multiplicative Blend (Multiplicative blend / Multiplicative composition / Blend DstColor Infographic that clearly illustrates the basic processing flow and mechanism of Zero) in Japanese notation
Detailed mechanism and operating principle
Change the material's blend mode to "Multiply" (specify `Blend DstColor Zero` in the shader code), multiply the shadow color by the ground color, and dye it dark while leaving the ground details intact.