Radiosity.

In this tutorial, we'll attempt to mimic radiosity's lighting effect by manual placement of lights.

Radiosity has reached "buzz word" status over the years, but it is an important part of making the next step in scene lighting. It essentially mimics real-world light "bouncing" to produce much more realistic lighting by way of indirect illumination. Look throughout the room you're in now. You'll find significant portions of the room being lit indirectly, where there is no direct line of sight from a light source to the surface. This is accomplished due to the light indirectly bouncing around the room's surfaces to reach those spaces. You'll also notice that corners and creases receive less light due to the ambient occlusion.

Here is a quick video of what we'll outline in this tutorial.

The tutorial starts off word heavy, but it gets less and less so as we go.

Please remember that every scene is different as is every lighting setup so this is only to guide the understanding rather than a strict rulebook. Also keep in mind that I am a simple artist who knows only the basics of light, there is tons of documentation for 100% accurate reproduction but you don't have to make it look perfect, only to the point where it looks "right". Feel free to mess around with it and don't be afraid to add your own style to it!

Note: Being that this involves adding quite a few lights considering the small scene space, deferred rendering would be suggested.

1. The basic scene. We've all seen a shot like this before, especially as dynamic shadowing engines have become more common place. There is one dominate light source and the portions of the scene not being directly lit by the main light rely on ambient lighting for their light source. The problem with this method is that the ambient light gives no distinctive shading or contrast to the different contours, materials and shapes. It looks flat, dark and unrealistic. Increasing the ambient light will not solve the issue as it will only rob more depth from the scene.

2. Here we've placed three point lights across the main light's hot spot on the floor. This is to simulate the light's bouncing off the surfaces such as the floor, ceiling and window edges as well. Note that these lights will obtain some color detail from the carpet as it would in the real world. To determine the color keep in mind the surface's material as well as the main light's intensity and color. For this the lights will have a pinkish color.

3. We use the same method for the other hot spot. Looking a lot better already.

4. Just as the floor causes the light to bounce so does the ceiling. To simulate this, we'll place our lights near the ceiling to both cast bounce light onto the floor but also onto the surrounding walls and ceiling. This doubles as light bouncing from the ground or objects outside up into the room.

5. A subtler touch is creating the light bleed from the windows themselves onto the ceiling. This can be an effect of the ground outside bouncing directly up, or the window sills/blinds doing the same.

6. In the next two steps we'll take the boxes into consideration. The boxes would bounce color and light just the same as the carpet and we'll try to mimic this. This step replicates the light bouncing off the boxes towards the ceiling with the lights being more intense and saturated where the sun light hits the box directly.

7. This step is an attempt to give the boxes some indirect lighting as well as giving a very small bit of yellow tint to their surroundings from that indirect lighting.

8. This final step is so subtle you likely wouldn't notice it, but it does bring the scene to its full depth. Three spotlights have been added to the scene to cast shadows, either individually or by shadow group, from the boxes giving them a sense of space in the scene. As with every step from four on, this is entirely optional.

Here is our final scene.

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Here is the scene we've created to first show this technique:

And a screenshot of the difference:

If you have any questions feel free to ask in the forums!

Thanks!