Lambertian Surface

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Lambertian Surface

Page Contents

Description

The Lambertian Surface type Source Primitive allows a single surface in the model to emit rays with a Lambertian distribution. The spatial extents of the emitter are defined by the shape of the surface.

Every surface type has a "positive side" and a "negative side" that is unique for the given surface construction. When a surface is turned into an emitter using the Lambertian Surface Source Primitive, the rays will be propagated away from the surface into the "positive side" by default. Determination of the ray emission direction should be made by configuring the source with a relatively small number of ray starting positions (100 - 1,000) and then performing a Trace and Render so that the ray trajectories are drawn in the 3D view. By inspection, if the rays are propagating into the intended direction relative to the surface then no further action is required and the number of ray starting positions can be set to the desired value. If the rays are propagating in the opposite direction from what has been intended, then the ray directions can be reversed using the option provided on the Lambertian Surface Source Primitive dialog.

An example of the Lambertian Surface ray emission reversibility is shown in the images below.


Figure 1. Lambertian Surface emitting from a surface with the "Reverse ray direction" option set to False.	Figure 2. Lambertian Surface emitting from a surface with the "Reverse ray direction" option set to True.

Navigation

This feature can be accessed in the following ways:

•Menu > Create > Source Primitive > Lambertian Surface

•Right mouse click on the Optical Sources folder, select Create New Source Primitive > Lambertian Surface

•Toolbar button:

Controls

Control	Inputs / Description	Defaults
Logical Parent	Read-only. Specifies the source's parent node on the tree.	Optical Sources
Name	Name of the source as it will appear on the tree view.	Lambertian Surface N
Description	Description string that will be visible on the tree view.
Parameter Attributes
0	Total power of the source.	1.0
1	Physical units of the source power, specified as either Watts or Lumens. When Lumens are selected, the source wavelength attributes is forced to use the Random according to spectrum option.	Watts
2	Specifies the number of random positions from which rays will be emitted according to a Lambertian distribution. The random positions lie on the designated surface (parameter 3).	100
3	Allows selection of the surface that will emit rays with a Lambertian distribution using an Entity Picker Control. The selected node must be a surface, which is indicated on the object tree by the icon. Other node types are not allowed for use with the Lambertian Surface type Source Primitive.
4	Per the Description section, this option will reverse the direction of the ray emission relative to the emitting surface.	False
5	Allows the starting ray positions to be offset along their local surface normals by the given amount. The sign of the offset determines the direction of the ray offset relative to the surface (either positive or negative). This option is useful for cases when the rays are not desired to start exactly coincident with the emitting surface.	0
Wavelength Attributes
Single, List or Random according to spectrum	In the following descriptions, N is the number of positions on the surface (parameter 2) from which rays emit. When the Single wavelength option is selected, N random rays will be generated at the specified wavelength. When the List wavelength option is selected, N random rays will be generated at each of the active wavelengths with non-zero weights specified in the wavelength list. When the Random according to spectrum option is selected, N random rays will be generated and each ray will have a unique wavelength whose value is selected by using the designated spectrum as a probability distribution.	Single at the default wavelength
Source Draw Color	If the Single or Random according to spectrum wavelength option is selected, this setting controls the ray position and trajectory draw colors. If the List wavelength option is selected, this setting only controls the ray position draw color. Ray trajectory draw color is controlled by the color specifications in the wavelength List for each wavelength.
Polarization
Polarization	If checked, polarization data for the rays is maintained and stored.	Unchecked
Handedness	Sets the handedness of the polarization state (relevant for non-linear polarization states). If the ray is propagating towards you, the electric field vector rotates in a clockwise direction for Right handedness and counter-clockwise for Left handedness. Note that for linear polarization, the application of Left or Right handedness is arbitrary. The user may find that the UI display switches handedness depending on the angle of the linear polarization state entered, but this will have no impact on the resulting representation of the linear state.	Right
Ellipticity	Sets the ellipticity of the polarization state, 0 represents linear polarization and 1 represents circular.	0
Angle	Sets the angle of the polarization relative to the X axis.	90

OK	Accept settings and close dialog box.
Cancel	Discard settings and close dialog box.
Apply	Accept settings and keep dialog box open.
Help	Access this Help page.