Lamps

Next to lighting from the background and any object with an emission shader, lamps are another way to add light into the scene. The difference is that they are not directly visible in the rendered image, and can be more easily managed as objects of their own type.

Common Settings

Type

Currently Point, Spot, Area and Sun lamps are supported. Hemi lamps are not supported, and will be rendered as sun lamps.

Size

Size of the lamp in Blender Units; increasing this will result in softer shadows and shading.

Samples

For the branch path tracing integrator, this specifies the number of direct light samples per AA sample. Point lamps might need only one sample, while area lamps typically need more.

Max Bounces

Maximum number of times light from the lamp is allowed to bounce. Limited by scene-wide bounce settings

Cast Shadow

By disabling this option, light from lamps will not be blocked by objects in-between. This can speed up rendering by not having to trace rays to the light source.

Multiple Importance Sample

By default lamps use only direct light sampling. For area lights and sharp glossy reflections, however, this can be noisy, and enabling this option will enable indirect light sampling to be used in addition to reduce noise.

Lamp Types

Point Lamp

Point lamps emit light equally in all directions. By setting the Size larger than zero, they become spherical lamps, which give softer shadows and shading. The strength of point lamps is specified in Watts.

Spot Lamp

Spot lamps emit light in a particular direction, inside a cone. By setting the Size larger than zero, they can cast softer shadows and shading. The size parameter defines the size of the cone, while the blend parameter can soften the edges of the cone.

Area Lamp

Area lamps emit light from a square or rectangular area with a Lambertian distribution.

Shape

Shape of the lamp.

Rectangle

The shape of the lamp can be represented as a rectangle and changed with the “X” and “Y” values.

Square

The shape of the lamp can be represented as a square and changed with the Size property.

Light Portals

Area lamps can also function as light portals to help sample the environment light, and significantly reduce noise in interior scenes. Note that rendering with portals is usually slower, but as it converges more quickly, less samples are required.

Light portals work by enabling the Portal option, and placing areas lamps in windows, door openings, and any place where light will enter the interior.

In outdoor scenes most rays do not bounce much and just fly off into the sky and therefore, light portals are not helpful for outdoor scenes.

White Room model by Jay Hardy.

Sun Lamp

Sun lamps emit light in a given direction. Their position is not taken into account; they are always located outside of the scene, infinitely far away, and will not result in any distance falloff.

Because they are not located inside the scene, their strength uses different units, and should typically be set to lower values than other lights.