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Light Physics Theory
Light Physics Theory
johns3dhelp, added 2008-04-08 10:12:42 UTC 26,008 views  Rating:
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This page is about the nature of light, which applies to lighting in 3D software.

See also 3 point lighting

The principles discussed here can be applied to many areas such as photography, video, oil painting...

Light can be thought of as a wave (it's the visible part of the electro-magnetic spectrum). We see variations in the wavelength or frequency of light as variations in colour.

Humans can see waves from violet through to red, Violet (blue) being the shortest wavelength and red being the longest. Beyond these extremes lie ultra-violet and infra-red, which we cannot see. light wavelength = colour

Wave Addition

The diagram below shows that if we add two waves each with a value of 1 together, the resulting wave has a value of 2. It is twice as bright.

This principle can be applied to 3DS MAX. Lights add up in a linear fashion; the more you add, the brighter the scene becomes... so you have to turn their intensities down.

see below how the two lights on the teapot add up. wave addition


The image below shows what happens when you add light of different colours. Think of it like averages.. Say that red has a wavelength of 20, and yellow is 10. If they are mixed in equal proportion the result would be 15, orange. (10 + 20, divided by 2, = 15 ..the average!). I just made those figures up, but you can see how mixing colours works in a predictable, linear way. Mixing colours follows the rules of the colour wheel.

mixing colour

Light naturally gets dimmer the further it is from the source. This happens at an exponential rate, the inverse square rule, i.e at a distance of 1 metre the light will have a brightness of 1, at 2 meters it'll be 4 x dimmer, at 3 meters it'll 9 x dimmer, and at 4 meters it'll be 16 times dimmer. So, the further away from the light you get, the faster it gets even dimmer, until very soon you are getting so near to the edge of infinately dim that our bit-depth restricted computers just register it as zero, black.

Copyright John Hammond, 2008 Contact