Improved policy

Author: portsmouth

index.html

@@ -1124,17 +1124,17 @@
 * +-------------------------------------------------+ *
 *******************************************************
 
-The intensity of the EDF is controlled by a luminance and a color multiplier. The **`emission_luminance`** parameter controls the luminance the emissive layer would have when **`emission_color`** is set to (1, 1, 1) and in the absence of coat and fuzz. The **`emission_color`** acts as a multiplier, i.e. the HDR emission in the model color space is defined to have a color given by **`emission_color`** * **`emission_luminance`**, thus the resulting luminance may be less than the input parameter, or even zero if the **`emission_color`** is set to (0, 0, 0).
+The intensity of the EDF is controlled by a luminance and a color multiplier. The **`emission_luminance`** parameter controls the luminance the emissive layer would have when **`emission_color`** is set to (1, 1, 1) and in the absence of coat and fuzz. The **`emission_color`** acts as a multiplier, i.e. the HDR emission in the model color space is defined to have a color given by **`emission_color`** * **`emission_luminance`**, thus the resulting luminance may be less than the input parameter, or even zero if the **`emission_color`** is set to (0, 0, 0). Note that the **`emission_color`** components may exceed 1, in order to be able to plug in an HDR texture [^ingamut].
 
 Moreover, the overall material luminance may be further reduced in the presence of coat or fuzz, as they can absorb light coming from the emissive layer before it exits the surface. The emission from the top surface should in principle gain a directional dependence due to the combined effects of absorption, total internal reflection (TIR) and multiple bounces in the coat layer, and absorption in the fuzz layer. The combined effect should result mostly in darkening and saturation at grazing angles.
 
 Being an intensity, **`emission_luminance`** can be any value greater than or equal to zero. For convenience, we make the soft range $[0, 1000]$, corresponding to the typical range of home appliances.
 
 
-Emission params          | Label     | Type     | Range           | Norm          | Default       | Description
--------------------------|-----------|----------|:---------------:|:-------------:|:-------------:|----------------------------------------------
-**`emission_luminance`** | Luminance | `float`  | $ [0, \infty) $ | $ [0, 1000] $ | $ 0         $ | Emission luminance, in cd/m^2 (aka. nits)
-**`emission_color`**     | Color     | `color3` | $ [0, 1]^3    $ |               | $ (1, 1, 1) $ | Emission color multiplier
+Emission params          | Label     | Type     | Range             | Norm          | Default       | Description
+-------------------------|-----------|----------|:-----------------:|:-------------:|:-------------:|----------------------------------------------
+**`emission_luminance`** | Luminance | `float`  | $ [0, \infty) $   | $ [0, 1000] $ | $ 0         $ | Emission luminance, in cd/m^2 (aka. nits)
+**`emission_color`**     | Color     | `color3` | $ [0, \infty)^3 $ |               | $ (1, 1, 1) $ | Emission color multiplier
 
 ![](images/emitting_lava.png width=90% align=left) ![](images/emission_under_coat.png width=90% align=right)
 <div class="shifted-caption">
@@ -1605,7 +1605,9 @@
 
 [^lerp]:  Where $\mathrm{lerp}(a, b, t) \equiv (1 - t) a + tb$.
 
-[^ingamut]: Note that we assume that all RGB colors are in-gamut, i.e. have components in the $[0,1]$ range in the
+[^ingamut]: Note that we assume that all RGB colors are in-gamut, and that colors representing albedos have components in the $[0,1]$ range (otherwise RGB renderers do not produce sensible results). The `emission_color` however is the exception which is permitted to have arbitrarily large (positive) components, since it represents an arbitrary luminance.
+
+i.e. have components in the $[0,1]$ range in the
 specified color space.
 
 [^Jacobian]:  Omitting Jacobian factors.

parametrization.md.html

@@ -59,7 +59,7 @@
 | `fuzz_roughness`                      | Roughness           | `float`   | $ [0, 1]        $ |               | $ 0.5              $ |                  |
 | **Emission**                                                                                                                                          |
 | `emission_luminance`                  | Luminance           | `float`   | $ [0, \infty)   $ | $ [0, 1000] $ | $ 0                $ | nits             |
-| `emission_color`                      | Color               | `color3`  | $ [0, 1]^3      $ |               | $ (1, 1, 1)        $ |                  |
+| `emission_color`                      | Color               | `color3`  | $ [0, \infty)^3 $ |               | $ (1, 1, 1)        $ |                  |
 | **Thin-film**                                                                                                                                         |
 | `thin_film_weight`                    | Weight              | `float`   | $ [0, 1]        $ |               | $ 0                $ |                  |
 | `thin_film_thickness`                 | Thickness           | `float`   | $ [0, \infty)   $ | $ [0, 1] $    | $ 0.5              $ | $\mathrm{\mu m}$ |