This chapter deals with LightWave's various shadow types and properties. By the time you have finished this chapter, you should understand ray-traced shadows, shadow maps, and the effects of shadow sizes and softness and how they relate to the type of light source that creates them.

Among the following paragraphs are some of my greatest pet peeves - those things that make my skin crawl when I see or hear about them. These are basic concepts that will really mess you up if you don't fully understand them, so pay attention!

First, let's get a few things straight:

• There is no such thing as a light source that causes only hard-edged shadows. The shape of a shadow depends upon the shape of the object that is casting it, but the size and softness of the shadow is dependent completely upon the light source. A light capable of causing a completely hard-edged shadow must have zero dimension and be a point in space with no size or shape. While this light type may very well exist in a virtual environment such as LightWave, it certainly does not exist in the real world. All light sources have some size, even the tiniest light-emitting diode or electrical arc. All light sources, therefore, cause some amount of softness to occur in the shadow. This means that all lights are volume lights (which is like an area light shaped like a cube instead of a plane).
• Lights do not cast shadows. Lights never cast shadows. No light has ever cast a shadow. Well, that's not entirely true. If you put an ellipsoidal reflector spotlight in front of a lit 5K Fresnel, it will cast a shadow. My point? Only objects cast shadows.
• One light results in one shadow. I have seen numerous shots where a single light source existed in the plate, yet there were multiple shadows on the floor cast by multiple CG light sources. That's another dead giveaway that something isn't right. CG artists are not the only ones to make this mistake; gaffers make the same mistake on set.

These are real-world scenarios. As CG artists, we often find ourselves trying to simulate real-world lighting. You will never succeed unless you know that a completely hard-edged shadow is wrong, lights do not cast shadows, and one light source results in one shadow for each object. I know there are nitpicky people out there who will argue that a reflection can cause a second shadow from the single light source and that is true, but it could be argued that the "mirror" is a second light source. Let's not get into an arm-wrestling match about it. Physicists, be gone!