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..::global illumination::..

Note from the author: This article was written with 3ds max 4 in mind. It should be noted that later versions of 3ds max (version 5) contains a built in global illumination lighting system..

Lighting is one of the most important aspects in creating a realistic render; over saturated, it looks too fake, undersaturated, too bland. There are several radiosity renderers on the market today which can also cost an arm and a leg, and take an age to render. So we have to attempt to fake it somewhat.

Global illumination is the key to producing a realistic outdoor render (you would modify this to fit an indoor scene). Global illumination is similar to Ambient lighting; something of which you should avoid like the plague as it over saturates your render and makes it look flat. Also, it adds light to places where none may exist. Faking radiosity can be a bit of a pain to set up, due to calculating light bouncing and setting up directional light colours so for the meantime, we will stick with a global illumination setup.

The best, and simplest way, to create global illumination is by using a rig setup. This is a relatively simple method, which kind of emulates Ambient lighting, but with shadow casting lights, so any corners and dark areas will remain that way. Imagine a low poly Geosphere, with directional lights attached to every vertex, with all targets focused at the centre of the Geosphere; that’s the way it should be created. Use instancing when copying to ensure that any setting you apply to one, is applied to the others. Every light should have a relatively large falloff to encompass the target area, overshoot on to illuminate the rest of the scene, low intensity (as there are a lot of lights) low shadow map size and a high sample range to feather out the shadow.

The rig should also be set up in two separate stages; namely top and bottom halves. The top half should be the light emanating from the sun and other illuminative objects, such as the sky, walls (etc), and the bottom half for the ground. You don’t need as many ground lights as you would for the sky, just enough to provide adequate uplighting. Create these separately though, and instance them as before, so you can modify the top and bottom lighting individually. Generally, daylight rendering should consist of two colours, a hot (sun) and a cold (shadow, dark skies etc). Overall, a very light blue should suffice to break up the scene, but if you find that it still does not look just right, play around with the lighting setup; even resorting to making every light unique and feathering off colours from hot to cold, across the scene.

Slight material amendments can also make a lot of difference; one quick fix method would be to add a subtle Raytrace or Reflect/Refract map in the reflection slot, with falloff and a medium to high blur to act as slight illumination from other objects. Also, play around with anti-aliasing and specular bloom settings to remove any unwanted harsh edges. Finally, you could also take colours of objects, and place low intensity lights with the same (or less saturated) colours around them to illuminate other objects.

Enlarge ScreenshotThe rig should consist of more lights at the top than at the bottom, but maintaining similar settings.
Enlarge ScreenshotThe finished render. An additional ‘hot’ light has been added to represent the sun, and a Reflect/Refract map added to reflect the Sky Dome.

Initially published: 3D World magazine, Issue 10, March 2001.

Copyright © Pete Draper, March 2001. Reproduction without permission prohibited.

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