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As in the real world, wherever the sun doesn't shine, you need to install artificial lights.

As in the real world, so in Atmosphere 3D models - where the sun doesn't shine, you need to install simulated artificial illumination. In Adobe Atmosphere, invisible primitive objects are usually used to model sources of light (in Atmosphere jargon, light 'emitters').

But which primitive objects should you use? This demo compares (left to right) a cone, a cylinder and a cube, all used as the only emitters of light energy in each 3D modeled environment.

What to Do, Notice and Investigate

1. Which primitive gives the most illumination? Why?
2. Which shape gives the smoothest simulated lighting? Why?
3. Describe how the illumination decreases with distance from the source.

Which 3D primitive is Brightest? (all have equal 'Emits Light' settings)

Look not only at the room sides, but also at the sides and back of the vertical square.

One way of thinking about how bright different shapes will be (if they are all set to 'emit' the same amount of light) is to think of them as light containers.

A primitive object with greater volume 'contains more light'. Since all three of my shapes are the same size, the model cylinder will just barely fit inside the model cube, but has its corners removed - so it has less volume and thus puts out less illumination. Likewise, the model cone has less volume than the model cylinder of the same size, so it puts out even less.

It's almost like a can of paint, the more the volume of your full can, the larger the surface you can cover.

Which Shapes Give the Smoothest Illumination?

If your modeled light is bright, reflects from light colored surfaces, and your render settings are at "Preview' or 'Final' quality, all three primitives will give fairly smooth results. But there are small differences. The model cube will create more patterns in the light it emits. The model cylinder is next best and the cone gives the smoothest lighting. I suspect that the reason for these slight 'pattern' artifacts has to do with the corners - where the faces meet. A model cylinder or model cone with many faces has less abrupt changes in angle where the faces meet, creating less 'beaming' of the emitted light energy. But that's just my guess.

How Does Illumination Decrease With Distance?

If a light source is omni directional (i.e. does not emit concentrated 'beams') then the light 'obeys' the "Inverse Square Law". That is, at twice the distance, it will have 1/4 the brightness.

It might seem more reasonable that twice the distance would give 1/2 the light, but think about it a bit. Not only does the same light energy have to cover twice the width at twice the distance, it must also cover twice the height. Since the light spreads out both vertically and horizontally, it has to cover 4X the surface that it did before, so a measurement of brightness at a given distance will give 1/4 that measurement at twice the distance (ignoring other effects for the moment).

If you have trouble visualizing this, think of a balloon. You halfway inflate a balloon, then draw a square on it. If you inflate the balloon to twice the diameter, the square you drew must now contain 4x the area, because it got bigger both horizontally and vertically.

1. To light a larger area or more distant object, you need a bigger light source. It may not be enough to just make the source brighter. Your source is like a paint container, the bigger it is, the larger the surface it can cover.
2. A cone is the primitive shape that gives the smoothest illumination.
3. Light obeys the Inverse Square Law, because it expands both horizontally and vertically. At twice the distance, it is 1/4 as bright.
   

Which Adobe Atmosphere 3D shapes simulate illumination best?
My 3D modeled scenes will show you.