View Full Version : Lighting equations and color

08-30-2015, 08:54 PM
Every beginner tutorial I've seen so far does something like this:

Color of pixel = Color of material * (whatever BDRF and attenuation functions) * intensity of light
So let's say I had a pure blue material, RGB: [0, 0, 255].
If I put a really intense white light next to it, the color of the pixel ends up being [0, 0, 255].

But in real life, I took a bright white light very close to a blue piece of paper. The paper appears white, not solid, bright blue.

Also, let's say I have a pure red colored light RGB: [255, 0, 0], and I have a material that's purely blue, as in RGB: [0, 0, 255].

I tried putting a red light next to a blue piece of paper. When the light is very close, the paper appears red. If I move the light a bit away, the paper actually appears purple (red + blue = purple, makes sense).

What kind of lighting model accounts for these kinds of phenomena?

Alfonse Reinheart
08-30-2015, 09:58 PM
What kind of lighting model accounts for these kinds of phenomena?

The kind where you use accurate inputs ;)

In reality, there's no such thing as zero reflectance. So the blue paper in your example is not [0, 0, 255].

08-31-2015, 02:17 AM
Also, consider that most materials are colourless (white) when it comes to specular reflection. Coloured materials typically consist of diffuse-reflecting coloured particles suspended within a colourless specular-reflecting medium.