Shaders define both how an object looks by itself (its material properties) and how it reacts to the light. Because lighting calculations must be built into the shader, and there are many possible light & shadow types, writing quality shadersA small script that contains the mathematical calculations and algorithms for calculating the Color of each pixel rendered, based on the lighting input and the Material configuration. More info
See in Glossary that “just work” would be an involved task. To make it easier, Unity has Surface ShadersUnity’s code generation approach that makes it much easier to write lit shaders than using low level vertex/pixel shader programs. More info
See in Glossary, where all the lighting, shadowing, lightmapping, forward vs. deferred renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary things are taken care of automatically.
This document describes the pecularities of Unity’s lighting & rendering pipeline and what happens behind the scenesA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary of Surface Shaders.
How lighting is applied and which Passes of the shader are used depends on which Rendering PathThe technique Unity uses to render graphics. Choosing a different path affects the performance of your game, and how lighting and shading are calculated. Some paths are more suited to different platforms and hardware than others. More info
See in Glossary is used. Each pass in a shader communicates its lighting type via Pass Tags.
ForwardBase and ForwardAdd passes are used.Deferred pass is used.PrepassBase and PrepassFinal passes are used.Vertex, VertexLMRGBM and VertexLM passes are used.ShadowCaster pass is used.
ForwardBase pass renders ambient, lightmapsA pre-rendered texture that contains the effects of light sources on static objects in the scene. Lightmaps are overlaid on top of scene geometry to create the effect of lighting. More info
See in Glossary, main directional light and not important (vertex/SH) lights at once. ForwardAdd pass is used for any additive per-pixel lights; one invocation per object illuminated by such light is done. See Forward Rendering for details.
If forward rendering is used, but a shader does not have forward-suitable passes (i.e. neither ForwardBase nor ForwardAdd pass types are present), then that object is rendered just like it would in Vertex Lit path, see below.
Deferred pass renders all information needed for lighting (in built-in shaders: diffuse color, specular color, smoothness,
world space normal, emission). It also adds lightmaps, reflection probes and ambient lighting into the emission channel. See Deferred Shading for details.
PrepassBase pass renders normals & specular exponent; PrepassFinal pass renders final color by combining textures, lighting & emissive material properties. All regular in-scene lighting is done separately in screen-space. See Deferred Lighting for details.
Since vertex lighting is most often used on platforms that do not support programmable shaders, Unity can’t create multiple shader variants internally to handle lightmapped vs. non-lightmapped cases. So to handle lightmapped and non-lightmapped objects, multiple passes have to be written explicitly.
Vertex pass is used for non-lightmapped objects. All lights are rendered at once, using a fixed function OpenGL/Direct3D lighting model (Blinn-Phong)VertexLMRGBM pass is used for lightmapped objects, when lightmaps are RGBM encoded (PC and consoles). No realtime lighting is applied; pass is expected to combine textures with a lightmap.VertexLMM pass is used for lightmapped objects, when lightmaps are double-LDR encoded (mobile platforms). No realtime lighting is applied; pass is expected to combine textures with a lightmap.