Light Properties

Thea light properties can be configured from a separate dialog. When a light is clicked in the Rhino viewport, the Thea light properties page is shown in the properties page. Depending on the light type, the appropriate controls are shown. Light properties are divided in five categories which are: General, Emitance, Custom Light Evaluation and Container.


Enable: Enables/Disables the light.
Shadow: Enables/Disables shadow casting.
Shadow > Soft Shadows: Definges whether the light will have soft shadows or not.
Shadow > Radius (m): Defines how soft the shadows will be. Higher value result in softer shadows.

Emittance Properties

Color: Sets the color of the light.
Power: Defines the power of the emittance along.
Power > Units: Defines the units that will be used for the given power.
Power > Efficacy: Defines the energy loss of the emitter. A value of 683 lm/W corresponds to lights without energy loss.
Passive Emiter: The emitter will not cast light into the scene but one will be able to still see the emitter 'lit'. (Only for Rectangular & Cylindrical lights)
IES: Loads and IES file. IES files describe light's emission according to measured goniometric data. (Only for Rectangular & Cylindrical lights)
IES > Filename: The path to the IES file.
IES > Multiplier: Modifies the intensity of the IES light.
Attenuation: Defines the attenuation type of the emitter. For physically accurate results, the default value (Inverse Square) should be used.

Custom Light Evaluation

Custom Light Evaluation allows the user to select which components (such as Diffuse, Translucent, Reflectance, Transmittance, and SSS) will be evaluated for a given material and light, thus removing unwanted contributions and accelerating render times.


The assign container options allows the user to assign a material as the container of the camera. By default, it is set to Global Medium but when a camera is inside an object with a material using medium, the image will render black, unless we assign that specific material to the container of the camera.
Assign Container: Select the material from the list that will be assigned as a container for the camera.