Light and Surfaces

A camera measures light, not objects

One ray in, a spray of rays out

Matte surfaces follow Lambert

Glossy surfaces add a highlight

A vision engineer renders two spheres under the same lamp. One sphere must look like unglazed chalk and the other like a polished snooker ball. Which combination of models fits the two spheres?

A lamp sits up and to the left of a horizontal surface. The direction from the surface toward the lamp is $\mathbf{p} = (-0.6, 0.8)$ and the surface normal is $\mathbf{n} = (0, 1)$. Using $\mathbf{r} = 2(\mathbf{p} \cdot \mathbf{n})\mathbf{n} - \mathbf{p}$, which mirror direction does the surface send the light into?

A matte patch has albedo $a = 0.8$. A lamp delivers $\ell_{\text{in}} = 5$ units of light arriving with $\mathbf{n} \cdot \mathbf{p} = 0.5$. Under the Lambertian model $\ell_{\text{out}} = a \, \ell_{\text{in}} \, (\mathbf{n} \cdot \mathbf{p})$, compute the reflected power and write it as a decimal.