Controls

$\color{goldenrod}{d}$ Diffuse
$\color{blue}{f_0}$ Specularity
Alpha
Roughness Isotropic
$\color{red}{m_x}$ X Roughness
$\color{green}{m_y}$ Y roughness
Light vector $\textbf{l}$ azimuth
Light vector $\textbf{l}$ altitude
Sun (right) rotate by draging mouse
Sun azimuth
Sun altitude
Exposure

BRDF: $ f(\textbf{l,v}) = \color{goldenrod}{d} (1-F(\langle \textbf{v,h} \rangle))+\frac{F(\langle \textbf{v,h} \rangle) \, D(\textbf{h})}{4 \langle \textbf{n,h} \rangle \, V(\textbf{l,v})} $
Fresnel: $ F(\langle \textbf{v,h} \rangle) = \color{blue}{f_0} + (1-\color{blue}{f_0}) (1-\cos(\textbf{v,h}))^5 $ $ \qquad with \; \color{blue}{f_0} = \bigl(\frac{1-n}{1+n} \bigr)^2 $
Normal Distribution: $ D(\textbf{h}) = \frac{1}{\pi \, \color{red}{m_x} \, \color{green}{m_y} \, \cos^4(\textbf{h,n})} * e^{ -tan^2(\textbf{h,n}) \Bigl(\frac{\cos^2 \phi_h}{\color{red}{m_x}^2} + \frac{sin^2 \phi_h}{\color{green}{m_y}^2} \Bigr) } $ $ \qquad with\;\cos\phi_h = \langle \textbf{t,h} \rangle, \; \sin\phi_h = \langle \textbf{b,h} \rangle $
Viewable: $ V(\textbf{l,v}) = (\cos(\textbf{l,v}) \, \cos(\textbf{v,n}) )^\alpha = \max{ (\langle \textbf{l,n} \rangle \langle \textbf{v,n} \rangle) } $
Vectors: $\textbf{v}$: view, $\textbf{l}$: light, $\textbf{n}$: normal, $\textbf{t}$ tangent, $\textbf{b}$: bitangent, $\textbf{h}$: half vector between $\textbf{v}$ and $\textbf{l}$

What does BRDF stand for?

Which rules must a BRDF obey?

Snell's law
Helmholtz reciprocity
Energy conservation
Law of superposition

What does 'bidirectional' mean in terms of a BRDF?

$ f(\textbf{l, v}) = f(\textbf{v, l}) $
The resulting reflections look the same from all directions
$ \forall\textbf{l}, \quad \int_\Omega{ f(\textbf{v, l}) \cos \theta \quad d\textbf{v} } \le 1 $
The reflection stays the same regardless of the light direction
The BRDF reflects more light in two specific directions

Which statements are correct?

Specularity affects the width of the highlight
Shininess (of the Phong model) affects the width of the highlight
Specularity affects the brightness of the highlight
Shininess (of the Phong model) affects the brightness of the highlight