| General | Shadow Map | Area | Photon
Every light posesses a basic set of properties which can be defined here. You can choose the type of light to use and define attributes such as light contribution, shadow map usage, selective, area light, and photon properties, etc. It is important to keep in mind that it is the job of the light shader (such as the default Soft Light shader) to implement the characteristics of the light source by controlling light functions such as color, spread, shadows, falloff, and so on.
Specifies what type of light you are editing; you can define basic light characteristics.
Generally, it is said that there are three types or components of light that contribute to the illumination of 3D objects in a scene: ambient light, diffuse light, and specular light. By default, most of the preset lights are set to produce both diffuse and specular lighting.
Ambient |
Enables ambient light for the light source. Light that comes from all directions and averagely brightens the lit areas of an object's surface. Objects appear flat when lit by ambient light alone. |
Diffuse |
Enables diffuse light for the light source. Light that has a position in space and comes from a single direction. When diffuse light touches the surface of an object, it scatters and reflects evenly across that surface. If Specular is off, the light will appear much softer. |
Specular |
Enables specular light for the light source. Light which reflects more intensely along and around the angle of reflection from a surface and produces a bright spot or highlight at the point of reflection. The intensity of the specular reflection is dependent on the material the object is made of and the strength of the light source that is contributing the specular light. If Diffuse is off, the light will appear harsh and brighter. |
Selective Light |
Specifies whether the light is selective and whether the selected objects are included with or excluded from the light. Objects to be affected by a selective light are stored in the Associated Models group of a light. Inclusive: Illuminates only those objects selected in the Associated Models list. Exclusive: Illuminates all objects except those selected in the Associated Models list. |
Allow Autokey during Navigation |
Allows navigation (zooming, panning, etc.) to be keyed automatically using autokey while looking through the light in a 3D view. This works only with spotlights. For a complete description, see Autokeying Camera Navigation [Basics]. |
Controls how shadows are created by a shadow map for the selected light.
Use Shadow Map |
Activates shadow map properties. |
Resolution |
Specifies the resolution (in pixels) of the computed shadow map. |
The Render settings are used when rendering to file or in the render region, while the Viewport settings are used in High Quality display mode.
Softness |
Creates soft shadows by defining a penumbra area. The penumbra is the "secondary" shadow that is cast when only part of the light is blocked by the object. |
Samples |
Specifies the number of samples to be calculated. Soft shadows are produced by distributing samples in a region of the shadow map. For the viewport, this value is clamped by the environment variable XSI_HIGH_QUALITY_VIEWPORT_MAX_SHADOW_SAMPLES. |
Volumic shadow maps, instead of simply storing the distance from the light to the first object hit, will raymarch through the scene from the light origin until a fully opaque object is hit. Along the way it stores the changes in color or intensity along with the depth at which the change occurred.
Volumic shadow maps are useful when rendering shadows for geometry hair.
Contains settings that define area light options for point and spotlights. The Area Light options are available in the Light property editor.
Area Light |
Activates area light properties for the selected light. |
Visible in render |
Makes the light-emitting surface visible in the rendered output (rendered frame, preview, render region, and so on). This is useful when you want area lights to appear in reflections. Note that the rendered area light uses the light color and intensity defined in the light shader's property editor (by default this is the Soft Light shader). |
Geometry |
Sets the shape of the area light source. Rectangle: Emits rays from a rectangular area. A rectangle area light is specified by two vectors that describe the lengths of the edges. The light icon appears with a rectangle around it. Disc: Emits rays from a disc-shaped area. A disc area light is specified by its normal vector and a radius. The light icon appears with a circle (disc) around it. Sphere: Emits rays from a spherical surface. A sphere area light is specified only by its radius. The light icon appears with a sphere around it. Cylinder: Emits rays from an open-ended cylindrical surface. A cylinder area light is specified by its axis and radius. The light icon appears with a cylinder around it. Cylindrical area lights are always open at both ends. Object: Emits rays from a surface defined by the shape of a geometric object in the scene. All points on its surface emit light uniformly. It is generally a good idea to keep the triangle count of the object as low as possible for maximum performance. The Samples usually have to be set much higher for object lights. User: User-defined area lights are intended for use with custom light shaders. This option allows the custom light shader to completely control all the light sampling. User-defined area lights rely completely on a specialized light shader to select sample points on the surface, cast shadow rays at those points (if required), and return the illumination from the points. These lights are treated like point lights, without origin or direction. It is the responsibility of the light shader to set the origin and direction as necessary, including any dependent values such as distance attenuation. Also, in Flat Light Mode, the Soft Light shader requires that the User option be enabled, otherwise, back faces are not lit properly. |
Object |
Specifies the name of the object being referenced by the area light. |
Pick |
Allows you to choose a geometric object in your scene that will be used to define the shape of the area light. |
Area lights use Quasi-Monte-Carlo sampling patterns taken in the U and V directions of the light area. Each area light is sampled multiple times, therefore, the sampling level defined for the render pass can be lowered even for high-quality renders.
Low UV sampling is useful when you want to optimize the amount of samples used for an area light that's illuminating a point after a given number of reflection and refraction levels. For example, when an object is being lit from behind one or more semi-transparent planes.
Controls indirect lighting and caustic highlights.
To render caustics, you must also set the Caustic options for the objects that receive and transmit the effect, as well as activate caustics on the Photon page of the mental ray Render Options Property Editor and/or the Render Region Options Property Editor.
Caustics |
Activates caustic lighting properties on the light. |
Global Illumination |
Activates global illumination properties on the light. |
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