What are the two hemispheres that we're considering? I'm having trouble visualizing this.
mpotoole
The BRDF $f(\omega_{in},\omega_{out})$ is defined over two hemispheres: one hemisphere represents the set of incident lighting directions $\omega_{in}$, and the second hemisphere represents the set of outgoing lighting directions $\omega_{out}$. The reason that its a hemisphere (and not a sphere) is because the angle between the normal and incident/outgoing directions has to be less than 90 degrees. Otherwise, the light rays will pass through the surface.
What are the two hemispheres that we're considering? I'm having trouble visualizing this.
The BRDF $f(\omega_{in},\omega_{out})$ is defined over two hemispheres: one hemisphere represents the set of incident lighting directions $\omega_{in}$, and the second hemisphere represents the set of outgoing lighting directions $\omega_{out}$. The reason that its a hemisphere (and not a sphere) is because the angle between the normal and incident/outgoing directions has to be less than 90 degrees. Otherwise, the light rays will pass through the surface.