Demo 3 - Those Useful Long Emitters in 3D Models

When you need to 3D model simulated evenly illuminated indoor spaces with Adobe Atmosphere, nothing works better than an invisible long source. These primitive objects are usually placed just under the top surface, pretty much the whole length of the space.

Often the top of this long source is painted black, so it does not create a 'hot spot' above it. Better yet, control each face of the primitive separately and turn off emitting where you don't want hot spots. This gives more even 3D model lighting and a 'cleaner' look, if your reflecting boundaries are light in color, or darker more somber light, if not. Think 'supermarket Vs pool hall'. Both use long sources, but in different ways and with different ceiling and wall reflectivity.

Once again, Adobe Atmosphere's radiosity rendering shows how well it simulates the real world!

What to Do, Notice and Investigate

Fly around these 3 demo environments and study them closely.

Which environment controls illumination the most? Why?
Notice how even and controlled the light is in all 3 environments. Why?
Could these 3 uses of a long source be combined in one room?

1. Which Environment Controls Illumination the Most?

The line source in the left environment. There, 3 sides of the primitive are painted black (yes, even the bottom).

2. Why is illumination So Even and Controlled When You Use Long Sources?

Without going all geeky about radiation patterns and such, let's just say that when you line up several emitters into one longer one, the radiant energy 'adds up' in one direction, but not in the other. Also, such long primitives don't have to reflect as many times to reach all parts of your environment.

Remember that large sources should be set to a lower brightness, so as not to 'overpower' the environment.

3. Could All 3 Ways of Using Long Sources Be Combined In One Room?

Sure. Typical modern indoor areas often do. Think of a tavern, with recessed lighting behind the bar, a line source hung over the pool table and maybe some fluorescent tubes run around the top of the walls.

What to Remember

Be creative in building invisible emitters. Your neighborhood supermarket has to use dozens of bright, small sources across their ceilings - because that's all anyone sells inexpensively. But you can do the same job with one big dim light.
A long emitter behaves differently than a cube or other compact shape.
Paint some surfaces of your emitter primitives black, to control where light falls. Or better yet, turn off emission from those surfaces. That will also lower your render time and decrease scene file size.

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