##### Blinn-Phong Reflection Model
1. Specular highlights Term 高光
1. Intensity depends on view direction
• Bright near mirror reflection direction
2. V close to mirror direction <–> half vector near normal(h)
• Measure “near” by dot productof unit vectors
3. Formula: $L_s = k_s(I/r^2)max(0,<n,h>)^p$
• What is the p in $max(0,<n,h>)^p$ for? Make it real:
• If $\alpha$ is too big, $<n,h>^p$ is small.
2. Ambient Term 环境光照
• Assumption: Shading that does not depend on anything
• Add constant color to account for disregarded
illumination and fill in black shadows
• This is approximate / fake !
• Formula: $L_a=k_aI_a$
3. Blinn-Phong Reflection Model:
• $L=L_a+L_d+L_s$

• Triangle face is flat — one normal vector
• Not good for smooth surfaces
• Interpolate colors from vertices across triangle
• Each vertex has a normal vector (how?)
• Interpolate normal vectors across each triangle
• Compute full shading model at each pixel
• Not the Blinn-Phong Reflectance Model
1. Defining Per-vertex Normal vectors 怎么定义逐顶点法线
• Simple scheme: average surrounding face normals
• Formula: 法向量加权平均 $n_v=\frac{s_i\times \sum_iN_i}{||\sum_iN_i||}$
2. Defining Per-Pixel Normal vectors 怎么定义逐像素法线
• Barycentric interpolation (introducing soon) of vertex normals

## Texture Mapping 纹理映射

• Surface are 2D, texture is a graph
• 每个模型上的点对应纹理上的坐标(u,v),一般都映射成0~1