"Paint" Cloud
Cloud Type
Mesh-Based Cloud Modeling
Mesh＋腐蚀等算法。
Pros
- High quality
Cons
- Overall expensive
- Do not support dynamic weather
现在已经没人用了。
Billboard Cloud
半透明插片＋\(\alpha \) 混合
十年前常用
Pros
- Efficient
Cons
- Limited visual effect
- Limited cloud type
Volumetric Cloud Modeling
Pros
- Realistic cloud shapes
- Large scale clouds possible
- Dynamic weather supported
- Dynamic volumetric lighting and shadowing
优点：(1) 全动态，CPU 实时生成。(2) 云可以表现出很多变化
Cons
- Efficiency must be considered
局限性：(1) 复杂 (2) expensive
Weather Texture
texture＋厚度 channel
对 texture 做挠动可以产生云的变化。
Noise Functions
Cloud Density Model
用低频 noise 雕刻出造型，再用高频加上细节。
Rendering Cloud by Ray Marching
不会把云转成 Mesh 去渲染，而是当作大气来渲染。
但由于云的通透性很低，可以对公式作大量假设和简化。
本文出自CaterpillarStudyGroup，转载请注明出处。
https://caterpillarstudygroup.github.io/GAMES101_mdbook/