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I guess I am somehow stuck with a basic question where I just don't get the correct answer.

The Phong illumination model contains an ambient, diffuse and specular part.

Each part contains a multiplication of the color of light (ambient or source) with a coefficient (ambient, diffuse, specular)): I * coe

The light and the coefficents consist of the r,g,b color channels:

I_r * coe_r
I_g * coe_g
I_b * coe_b

Assuming a light would be green (0,1,0) and the coefficient (doesn't matter which) is blue (0,0,1) the result would be black (0,0,0).

How does this make any sense?

Rabbid76
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Allwo
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1 Answers1

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A blue object only reflects blue light. If you light it using white light, which contains all colors, it reflects only the blue light, so that is why it appears blue to the viewer. If you shine a light that has no blue component on a blue object, no light will be reflected.

In real life, lights and pigments are never "pure", and a object will not appear completely black in these situations. However, in the world of computer graphics, this can happen easily.

tkerwin
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  • In computer graphics though, it could be possible if the "blending" is according to HSL channels NOT to RGB channels.... Real life blending uses HSL system. – Xerix Mar 21 '19 at 00:51