Lighting: It’s more technical than you think

Header image retrieved from https://www.dailydot.com/parsec/most-anticipated-games-2017/

Before any 3D scene can be fully rendered or composited, lighting must be applied to the scene, not only for it to come to life, but also so it does so with some degree of realism. Although technical, lighting is one of the most aesthetic choices in the 3D production pipeline. Considerations into the mood of the scene (atmosphere, colour palette, etc.) and the realism must come together in order to create a polished finish. Lighting artists can use a variety of techniques to achieve this, mainly through six lighting types – each with a specific use and purpose.

pointlight-spinner

Point, or omni lighting, is one of the most common lighting types found in 3D software, and emits light in all directions, with no specific shape or size. This method can simulate omnidirectional light sources, with a smooth fallout in all directions, or creating a light that has a single point as its source (Pluralsight, 2014). Examples of ideal sources using this method include lamps, Christmas tree lights or candles. Point lights can add “fill lighting” to a scene.

mental-ray-illumination

Example of volume lighting. Retrieved from http://polygonblog.com/mental-ray-lighting/

Similar to an omni light, volume lighting casts rays with a specific directionality from a certain point. However, a volume light operates within the constraints of a specified shape and size (often a geometric primitive – cube, sphere, etc.), affecting its degree of falloff. If a specific object is to be illuminated, the volume light will need to be placed in very close proximity to it (Slick, 2014). Essentially, its light will only reach surfaces within its volume. Whilst Maya is the only 3D application that has an option called Volume Light, most other applications achieve volume lighting through the different settings of a given light type (Pluralsight, 2014).

licht_3

Ambient lighting, used to illuminate the areas outside of the main light sources. Retrieved from http://www.easterngraphics.com/pcon/en/wp-content/uploads/2011/11/Licht_3.jpg

Ambient lighting is useful in elevating diffuse illumination, as its soft light rays are cast in every direction with no specific directionality – additionally meaning it casts no shadows (Slick, 2016). It typically operates as more of a “secondary” light that comes in from all angles, whilst being applied to all objects in the scene. Ambient lighting is useful for filling in areas that do not have enough illumination at its base level (Pluralsight, 2014). It is comparable to the dusk after the sunset.

closeup16cf2d70-6aa8-4613-8eae-cd9ab5ce612blarge

Area lighting is described as a “physically biased light that casts directional rays from within a set boundary,” (Slick, 2016). These lights are emitted within a set boundary of a certain shape or size, typically rectangular or circular, and used in visualisation of architectural models or in product lighting, or in simplistic rectangular lighting sources such as light shining through a window or a ceiling light (3D Ace, 2013). Whilst other lighting types emit light from a single point, an area light emits from an entire area, creating a realistic environment (Pluralsight, 2014). The soft-edged shadows produced by this technique aid in making the model look realistic. Unfortunately, this light has a higher rendering time than other methods, mainly because the extra light points need to be processed (Pluralsight, 2014). Area lights differ from other lighting types as they do not emit parallel rays of light, whilst still retaining directionality.

reverberes1

Spot lighting simulating a cone of light from a streetlamp. Retrieved from http://www.imarend.com/virtual/tutorials/BlenderLight/reverberes.gif

Spot lighting, similar to their real-world counterparts, emits a direct cone-shaped light from a single point in the 3D space (Slick, 2016). The width of the cone angle can be controlled to determine how much of the area is illuminated. The closer the object is to the spot light, the more illuminated it is, and vice versa, with the softness of the light dependant on how wide the cone is (Pluralsight, 2014). Due to its customisation, using a spot light can create a unique illumination depending on the scene required. Common uses for spot lighting include three point lighting, which incorporates three spot lights to generate studio lighting effects (Pluralsight, 2014). Light fixtures, especially those with visual falloff (light to dark), such as desk lamps, can be created using spot lighting as it is characterised by a focused ray of light (3D Ace, 2013).

800px-cycles_270_volume

Parallel lines of directional lighting visible in this image. Retrieved from https://wiki.blender.org/uploads/thumb/6/6d/Cycles_270_Volume.png/800px-Cycles_270_Volume.png

Directional lights inhabit a set or static location in the 3D scene, and project a cone-shaped light in a specific direction. The parallel rays emitted from directional lighting is emitted from a single direction, and are typically used to simulate direct sunlight. Because this lighting method only denotes a distant light source, it not characterised by X, Y and Z co-ordinates, rather only its rotation values, which can be rotated in any direction. This rotational attribute has bearing on how the scene is illuminated (Slick, 2016). Typically, this lighting type is used in scenes to illumine large, open areas such as open plan cities or fields, as it is very far away and centred. In programs like 3Ds Max, directional lighting types are referred to as free directional lights or target directional lights (Pluralsight, 2014).

Light added to a scene composition is customisable, with sliders dictating colour, intensity and decay. Intensity is the measurable level of potency of the light source, calculated in real-life units such as lumencandela, and lux (Chopine, 2012, p. 181).

Decay is the measuring of how light dims, or decreases, depending on the distance from viewing source, and can be defined by three distinct types: linear, quadratic and cubic.cool2.png

Retrieved from Chopin, 2012, p. 183.

Linear decay dictates that the light becomes dimmer in direction proportion to the distance between light source and viewing source, and is also known as inverse decay. Quadratic, or inverse cubed decay, similar to real-world light, decays in proportion to the square of distance; with the lighting brighter to the source, but quicker to dim as it drifts away (Chopine, 2012, p. 184). Cubic distance, in proportion to the cube of the distance, means the light gets faster than its reality counterpart, and thus a realistic lighting situation should rely on quadratic decay in most cases (Chopine, 2012, p. 184).

After ensuring that the object models and lighting are cohesive, the artists can move onto rendering and compositing.

Further tutorials… https://www.lynda.com/Character-Animation-tutorials/Basics-lighting-3D/385431/433626-4.html

References used:

3D Ace, (2013), How to Light a 3D Scene: Overview of Lighting Techniques. Retrieved from https://3d-ace.com/press-room/articles/how-light-3d-scene-overview-lighting-techniques

Chopine, A., (2012) 3D Art Essentials: The Fundamentals of 3D Modeling, Texturing, and Animation

Pluralsight, (2014) Understanding Different Light Types. Retrieved from https://www.pluralsight.com/blog/film-games/understanding-different-light-types

Slick, J., (2016) Guide to 3D Lighting Techniques for Digital Animation: Introduction. Retrieved from https://www.lifewire.com/3d-lighting-techniques-2090

*All image references not listed are retrieved from:
Cahill, P. (2014) 3D Lighting Types. Retrieved from http://www.onlinedesignteacher.com/2014/07/3d-lighting-types_49.html

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