Tutorial: Advanced Lighting Techniques Part 1

Posted by Montree T. 16 November 2003 5:00 pm

Advanced Lighting Techniques Part 1

by Montree T. (easyyong@hotmail.com) - Smoke3dStudio
If you wish to only use standard lights, the following method is necessary to make the scene look more realistic and detailed. In this tutorial I will show several examples to guide you though the process of simulating advanced realistic lighting. The most important thing however is to first make your own observations of lighting in photographs. (Not from any GI computer generated images.)

Using standard lights we have:

Omni lights with a spherical shaped beam that emits in all directions,

Spotlights with conical or pyramidal beams,

and direct light (cylinder or cube beams).

The mixture of these kinds of lights can produce an abundance of lighting and shadow effects.

Note: The following techniques may produce only lighting effect, you may need to create another group of lights to cast the shadows.

Two spot lights combined together to create a halogen light effect. Two cone layer effect.

A group of omnis, as shown in the picture below. Some are created to be direct illumination from cope light and some are created for simulating indirect illumination around the area.

1. Tube lights

This is based upon my own observations on a tube lights. The beam of the light looks like the picture below.

I place two free direct lights on the left and right of the cylinder to create the effect on the sides and put an omni in the middle. Use uniform scale to fit the omni's attenuation onto the cylinder. This creates the effect of the light from the top and bottom part of the cylinder. Change the shadow density to be negative so that better area shadow are created by the light.

2. Ring Light

In my previous example, I just mentioned only the far attenuation, but in this case we need to use the near attenuation to create the ring effect. I use and omni and turn on the near attenuation. The area in between the near attenuation has no light so the effect looks like a ring.

The blue circle in the picture above indicates the range of near attenuation.

3. Sphere Light

The sphere light is easy to create. We just put an omni inside a sphere object (that is light source). The light emits from every surface on the sphere as its attenuation form is as same as omni, but its shadow depends on how big the light source is, so we need to adjust the shadow's softness to follow the size of the light source.

4. Environment Light

Environment light is light that is scattered around a scene. It's also considered as an area light as the light will effect in every part of the object.

A good example for this is skylight in an exterior scene:

"Skylight is the light from atmoshere, simulated by the reflectance of sunlight over the sky, cloud and everthing in the atmoshere. As the light is scattered and affected in every direction in atmosphere so we also considered it as a big dome of an area light in the scene in CG."

As mentioned in the previous example, first we imagine the area light shape as a 3d object (that we've assumed skylight shape is like a dome) and then place standard lights perpendicular to every surface on the object. In this case I choose freespots for faking the effect by placing them around the imagined dome. The dome light also result a good soft shadow effect.

1. Create a unit freespot light and change the color to light blue and enable overshoot.

2. Array and copy (instance) the light, following a half dome shape. In the example I use lesser numbers of spotlight to reduce the rendering time. (The more lights their are, the more realistic and detailed on shadows will be.)

3. Copy and mirror the spot light (no shadow casting) below the building. This is for green illumination from the green grass effecting on the buildings.