3D Lighting

There are many different light types to choose from in your 3D application of choice and knowing which one works best for your scene is key to creating a great render.[1]
Even though it's pretty easy to click the “create light," button in your 3D software package and place a light source in your scene, the reality of the craft is far more complex.
There are a number of well established 3D lighting paradigms, and the type of scene usually determines which one is most appropriate. For example, techniques that work well for an interior environment usually make very little sense for an exterior shot.
Similarly, "studio" lighting for product or character rendering requires a very different procedure from lighting for animation and film.
In the end, every situation is different, but certain light types work well for certain scenes.[2]


Point/Omni Light:
Point lights are the most common light types found in 3D software. A point light is very similar to an
incandescent light bulb that emits light in all directions. You can think of a point light as a sphere of
light filling an area. Objects closer to the light will be brighter, and objects further away will be darker.[1]
Point lights are great when you need to illuminate areas with a smooth falloff in all directions,
or create a light that has a single point as its source, like a lamp or candle.

Directional Light:
Unlike point lights, which occupy a specific location in the 3D scene, a directional light is meant to represent
an extremely distant light source (like the sun or moon). Rays cast from directional lights run parallel in
a single direction from every point in the sky, and are typically used to simulate direct sunlight.
Because a directional light represents a distant light source, its x,y,z coordinate means nothing
only its rotational attribute has any bearing on how the scene will be illuminated.[2]

Spot Light:
A spot light behaves exactly how it sounds, like a real spot light, and provides a very direct source of light.
One of the key benefits that you get when using a spot light is the directionally that you get from the light.
The spot light is emitted through a cone and you can control how wide the cone angle is which determines
how much of the area is actually illuminated. Objects closer to the spot light will be brighter,
and depending on the how wide the cone is the light will either be softer or harder.[1]

Area Light:
An area light is a physically based light that casts directional rays from from within a set boundary.
Area lights have a specific shape (either rectangular or circular) and size, making them very useful for
simulating florescent light fixtures, back-lit panels, and other similar lighting features. Area lights can be
used as photon emitters when using global illumination in Mental Ray, which makes them a popular
choice in product lighting and architectural visualization. Although area lights do have an overall directionality,
they do not emit parallel rays like a directional light would.[2]

Volume Light:
A volume light is very similar to a point light, emitted omni-directional rays from a single point.
Unlike a point light though, a volume light has a specific shape and size, which affect its falloff.
A volume light can be changed to any geometric primitive: a cube, sphere, cylinder or cone.
The volume light only illuminates objects within its volume. Meaning if you want the object to be lit up,
the volume light will need to be placed around the object.[1]

Ambient Light:
An ambient light casts soft light rays in every direction, and can be used to elevate the overall level of
diffuse illumination in a scene. It has no specific directionality, and therefore casts no ground shadow,
however it is not truly omnidirectional like a point light. Ambient light is relatively similar to the light
experienced at dusk, just after the sun has set.[2]


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