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# Phong's model

TLDR of Phong's model as per Blinn's paper:

$$\begin{split}
d &= \max\{0,~\langle N, L\rangle\},\\
s &= \langle N, H\rangle^{c_1},\\
i &= p_a + d p_d + s p_s,
\end{split}$$

- $i$ -- perceived **i**ntensity,
- $p_s$ -- proportion of **s**pecular reflection
- $s$ -- amount of **s**pecular reflection,
- $c_1$ -- measure of shininess of surface,
- $L$ -- light direction(?),
- $E$ -- **e**ye direction,
- $N$ -- surface **n**ormal,
- $H$ -- direction of maximum **h**ighlight/"**h**alfvector", $H = \frac{L+E}{\|L+E\|}$.