光的工作原理和阴影类型 学习笔记

知识要点：

emission, direct and indirect light bounces (both specular and diffuse), transmission, and absorption.

自发光，直接光，间接光反弹（包括高光和漫反射），半透明，吸收

以及阴影相关知识

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光的六大要素：

光度 光的强度

光位 光的位置

光质 光的质量 软硬 聚散 

光型 光的类型 背景光 主光 辅光 轮廓光

光比 物体明暗的亮度比

光色 灯光的颜色

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Emission自发光

Reflection

Light can bounce from the object, giving us reflected light. 

 Diffuse Reflection:

Specular reflection:

 Transmission 光线的传导

Transparency 透明

Translucency 半透明

Subsurface Scattering 次表面散射

Absorption 吸收

Direct and Indirect Lighting

 

 

 

So, how can we form an image using what we have discussed so far? Let’s take a look:

如何描述一个灯光照明~  来看看

 diffuse and specular bounces:

 

This is nice, but light in real life bounces more than once – we need to incorporate these extra bounces (indirect light) into our scene:

 

 When we combine everything together, we have our render:

 

So, what we need to represent light is the sum of direct lighting (diffuse and specular), transmission, and indirect lighting. We could also add some extra effects, such as caustics, bloom, motion blur, etc., but those are the basic pieces that we should keep in mind.

所以描述一个场景内的所有光源：直射光（漫反射和高光（镜面反射）），半透明和间接照明的总和。额外还可以有焦散，发光（bloom），动态模糊。。。等等。

 Reflections in Detail

Albedo 反照率 

被物质反射的百分比称作反照率（理论上没有100%反照率东西，避免纯白色）

Non-metallic materials (dielectric) 非金属

Metals  金属

Diffuse bounces carry the color of the object.

Specular reflections keep the color of light

 

 不同颜色的物体反射的高光颜色都是和光源的颜色一样的~  

Specular reflections look different depending on surface roughness.

Fresnel effect

This effect is called the Fresnel effect, and it basically means that surfaces are more specular when looked at at extreme angles. 在极端角度下 表面会更像镜面

 

 

 Metals

Metals are very, very dense，When light hits a metal surface, most of it bounces off

Some metals can also add a little bit of color to the reflected light making it look like they have a color (gold, copper, etc.), but in reality they are just modifying the color of reflected light: specular highlights keep the color of the light in non-metallic surfaces, but can be altered in metallic surfaces.

 

Combining Light Sources 合并光源

 This means that we can work on each light source separately and add them; light sources can be added linearly.

阴影：

form shadow  

shadows created on the surface of objects simply because they are less exposed to the light

cast shadow   

shadows created when an object or a part of an object gets between a source of light and another object. 

AO shadow

when an object gets close to another, light is less likely to reach the space in between objects, and that space looks darker. 

The brightness of shadowed areas will depend on how much indirect light we have in our scene

The shadow of this girl is very dark because there is only one light source (sun) and no surfaces where sunlight can bounce to fill it.

This woman has almost no shadow: the buildings, clouds, and rain are reflecting light everywhere.

 shadows can overlap

 Shadows can have smooth or hard edges

 

光度 luminosity 灯光的亮度

光位 灯光的位置

光质  光的聚散和软硬

 明显的光源方向 线条分明突出重点 阴影清晰 ，产生强烈对比 更有张力

 

 淡化主体，更柔美 和环境更加自然 有亲和力

 

 光型 灯光类型

 

 

 

 

 

 

 

 光比 物体亮部与暗部的差异

 

 光色 灯光颜色 色温和色调