Arion Render being a physically-based render engine, it doesn't impose any special limit on the possible color input.
For example, despite absolutely perfect white or fully saturated colors aren't present in the real world, Arion Render lets you uses that kind of color if you want. But the goal of this tutorial is to explain that you shouldn't, ever.
In the real world for example the whitest wall paint you can purchase has a reflectance of about 60-70%, which correspond to an RGB value (if completely uncolored) comprised between 150,150,150 and 180,180,180.
Naturally we are not obligated to use such low values, because it makes it difficult to clearly foresee what color we should use then for this or that material. But keep that in mind and consider pumping up your exposure if the render is too dark instead of using higher RGB values.
You may have already heard of this rule before, but perfect white has several problems:
- Bad-looking: It barely attenuates light, resulting in washed-out, contrast-less renders
- Slower: It forces the engine to use as many global illumination as it is allowed to, because of the previous point (light does not attenuate and just keeps bouncing).
- Wrong lights balance: It gives you the false impression that the lighting it too strong for white objects while too dark for other objects, leading to difficult light setups and bad-looking results.
In the examples below, we compare the same scene rendered with a perfectly white material and then with a reasonable value (RGB 220,220,220).
The maximum global illumination bounces was set to 1000 to show clearly how wrong that is.
|Perfect white||RGB 220,220,220 'white'||RGB 220,220,220: Exposure adjusted|
|This is a disaster, both in terms of contrast,|
realism but also in term of performance: This
render took almost 3 times longer to reach the
same sampling level as the one on the right.
|Barely 15% less reflectance than pure white|
yet such an immense difference!
The material appears gray, because it's the
exposure that is wrong, not the material.
|See how this both looks white and|
properly contrasted, as in a real photo?
That is the proper way of setting up
materials and overall look.
That case is special, as the entire scene is using a unique plain color material, the the rule remain true even if a single object should be 'white': Avoid perfect white.
The same principle applies for fully saturated colors, red in this example.
|Perfect red||RGB 220,0,0||RGB 220,0,0: Exposure adjusted|
Following these principles lead to several positive aspects:
- Realism: Materials are the way they should be, reflections are more intense and overall contrast feels better.
- Easier lighting setup: If the materials have more or less correct reflectance the light will behave more predictably.
- Performance: The engine doesn't need to bounce light more than necessary and renders faster.