Unity 2D模式灯光无效果的原因及3D与2D灯光差异咨询

Hey there! Let me break down why you're seeing this difference and clarify the steps you've already heard about.

Core Differences Between 3D and 2D Lighting #

The key issue boils down to how each mode handles surface orientation information:

• In 3D, every mesh has built-in normal data—each polygon (or vertex) tells the engine which direction it's facing. Lights use this to calculate things like angle of incidence, shadowing, and intensity falloff automatically. That's why your lights work right away in 3D mode.
• In default 2D setups, sprites are just flat, texture-covered planes with no inherent depth or normal info. The engine has no way to know how light should interact with different parts of the sprite—so it either ignores the light entirely or applies a uniform brightness, which looks like nothing's happening.

How to Get 2D Lighting Working #

The tutorials you watched are spot-on—here's a quick breakdown of why each step matters:

• Normal Maps: These are special textures that store "fake" normal data for every pixel of your sprite. Think of it as telling the engine, "This part of the sprite is angled up, this part is indented," etc. You can create them in tools like Photoshop, GIMP, or specialized sprite lighting tools by converting your original 2D art.
• Custom Materials: Most game engines require you to use a 2D-specific lit material instead of the default unlit one. This material will take your original sprite texture and the normal map, then use the normal data to calculate how light hits each pixel, creating realistic shadows and highlights.

Once you set those up, your 2D lights should behave similarly to how they do in 3D—reacting to the "pseudo-depth" from the normal map instead of treating the sprite as a flat slab.

内容的提问来源于stack exchange，提问作者jeep