[TA frost wolf \u may- hundred people plan] 2.4 traditional empirical lighting model

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This part follows Games101 It has been pushed in detail , Let's mainly look at the second half

Classification of illumination models

1. Illumination model based on physical theory ： Emphasis on the use of physical measurement and statistical methods , The effect is real , The calculation is complicated , The implementation is more complex ;
2. Empirical model ： Simulation of light , By simplifying and summarizing , To achieve acceptable results ;
   This chapter focuses on the empirical model approach

Diffuse reflection

Not affected by the viewing angle ,Lambert The lighting model is only for diffuse reflection ：

Specular reflection

Affected by the observation angle , Yes Phong Models and Blinn-Phong Model two these two models include diffuse reflection 、 Specular reflection 、 Three parts of ambient light , It is a relatively complete model at the beginning . The latter introduces half range vector based on the former, which reduces the computational complexity .

Phong Model ：

Blinn-Phong Model ：

The difference is that half way vectors are used in the green box , The calculation of half range vector is realized as follows ：

The ambient light

Generally, this part of lighting is simplified , Directly multiply the ambient color by the diffuse material .

Coloring method

The following content should correspond to Games101 Section on coloring methods , Fan BIE is plane by plane 、 Shading per vertex and per pixel , What we use is the surface difference 、 Vertex interpolation and normal interpolation implement the above parts .
The corresponding English names are ：

1. Flat shading
2. Gouraud shading
3. Phong Shading
   Pay attention to distinguish the Phong shading And previous Phong Model ,Phong shading Pay attention to the frequency of coloring , and Phong The model is to describe how to simulate the real lighting phenomenon .

Vertex normals

Vertex normals have not been figured out before , seen Games101 Then I realized that the normal sum or weighted sum of adjacent faces （ The weight is the area of adjacent faces ） Obtained .

summary

I followed the sixth chapter of the introduction essentials , Generally understand the implementation methods of various empirical lighting models .

I was stunned by the realization of energy conservation required in my homework , Finish later PBR Come back and make up . The application of energy conservation lies in ： Diffuse reflection formed when light hits the surface of an object , The sum of specular reflection and absorbed energy is certain , No matter how it changes, the overall strength remains unchanged .

It's a little hard to understand hundreds of people without a little foundation , Let's have a quick talk first 《 Introduction to topic 》 Well ,10 Within days .