Applying Properties

Surface Source Properties

A surface source is a surface that is designated to emit rays in a raytrace. There are five types of surface source properties in TracePro. Two types can emit discrete wavelengths (flux, irradiance) and two types can emit calculated wavelengths (blackbody, graybody). The fifth type, Surface Source Property, can emit either discrete wavelengths or calculated wavelengths.

You can make any surface in a TracePro model a source of rays for use in a raytrace:

1.Select a surface to which to apply a surface source property. You can make a surface selection in the System Tree or in the model window.

Note: If you apply surface sources to objects, TracePro will apply the property to each of the object’s surfaces.

2.Choose Define|Apply Properties to open the Apply Properties dialog box. You can also access the dialog from the Source tab in the System Tree or from the Define|Surface Source menu.

3.Select the Surface Source tab.

4.Specify the Surface Source property type. The option that you select changes the fields on the Surface Source tab. Select from the following:

•Surface Source Property (Figure 4.9),

•Flux (Figure 4.11),

•Irradiance (Figure 4.11),

•Blackbody (Figure 4.10), or

•Graybody (Figure 4.10).

•The Source Types are described below.

5.Select the Units (Flux or Irradiance source only).

6.Select an angular distribution (except for Surface Source Property type).

7.Select the Rays to be emitted. In most cases this is set to All.

8.Enter a value for the flux (Flux source) or irradiance (Irradiance source) or temperature (Blackbody or Graybody source).

9.Enter the minimum number of rays for any wavelength.

10.Enter the total number of rays for this surface source.

11.For a Surface Source Property Surface, select Discrete wavelengths or Calculated wavelengths.

12.Enter as many wavelengths as you need: type in each wavelength in μm, then click the Add button in the Wavelengths box or press the Enter key.

13.For discrete wavelengths, edit weights as needed.

14.For calculated wavelengths, edit #Inc as needed for each waveband. 15.Define as many surfaces to be source surfaces as you need.

a.Make a surface a source by first selecting Define|Apply Properties, or by clicking the right mouse button in the Model window and selecting Properties... from the pop-up menu. That menu opens the Apply Properties dialog box. See Figure 4.10 for a view of the Apply Properties dialog box.

b.Select the Surface Source tab and select a surface.

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Surface Source Properties

c. Fill in necessary fields to specify the source, and press the Apply button.

Flux and Irradiance Type Surface Sources emit discrete wavelengths, and Blackbody and Graybody Type Surface Sources emit calculated wavelengths. With a Surface Source Property surface source you can choose whether you want calculated or discrete wavelengths.

Also, you can remove the source property from a surface by opening the dialog box, selecting the surface with the mouse, then select Source Type <None> and click the Apply button.

FIGURE 4.9 - Surface Source Property Surface Source (shown with Discrete Wavelengths)

TracePro 5.0 User’s Manual

4.13

Applying Properties

FIGURE 4.10 - Blackbody Source (requires Calculated Wavelengths)

4.14	TracePro 5.0 User’s Manual

Surface Source Properties

FIGURE 4.11 - Flux Source (requires Discrete Wavelengths)

TracePro 5.0 User’s Manual

4.15

Applying Properties

Source Type	Source Property - Uses a Surface Source Property to determine the spectral
	distribution, units, and total flux or irradiance to be emitted by the surface
	source. Uses either discrete wavelengths (see Flux or Irradiance below) or cal-
	culated wavelengths (see Blackbody or Graybody below).
	Flux—The total power emitted by a surface. Flux source surfaces distribute
	the power uniformly over the surface area. The light rays are emitted from the
	surface at random positions. Flux source surfaces emit rays in discrete wave-
	lengths. A portion of the total flux is allocated to each wavelength according to
	the wavelength weight. The number of rays for each wavelength is calculated
	to give each starting ray approximately the same flux, regardless of wave-
	length.
	Irradiance—Irradiance source surfaces distribute power per unit area. Thus, a
	larger total area provides a higher total flux. They use discrete wavelengths.A
	portion of the total flux is allocated to each wavelength according to the wave-
	length weight. The number of rays for each wavelength is calculated to give
	each starting ray approximately the same flux, regardless of wavelength.
	Blackbody—Blackbody source surfaces require a temperature value and cal-
	culated wavelengths to calculate irradiance on a source surface. TracePro
	uses wavebands to approximate a continuous spectrum. It calculates a spec-
	trally-weighted wavelength to represent each waveband. In the calculation,
	TracePro distributes the number of rays per waveband to generate rays with
	approximately equal flux. The Min Rays field specifies the minimum number of
	rays assigned by calculation to each waveband.
	Graybody—Graybody source surfaces require a temperature, an emissivity
	value, and continuous wavebands to calculate irradiance on a source surface.
	TracePro uses wavebands to represent a continuous spectrum. It calculates a
	spectrally-weighted wavelength to represent each waveband. In the calcula-
	tion, TracePro distributes the number of rays per waveband to generate rays
	with approximately equal flux. A graybody calculation uses the value in the
	Emissivity field for determining power distribution over the surface. The Min
	Rays field specifies a minimum number of rays assigned by calculation to each
	waveband.
Units	Specify the type of units, either Radiometric or Photometric (Flux or Irradiance
	sources only).
Min Rays	Specify the minimum number of rays assigned (by TracePro calculation) to
	each wavelength.
Total Rays	Request a number of rays to emit from a surface source. For a Flux or Irradi-
	ance (discrete wavelength) raytrace, exactly the requested number of rays will
	be traced. For a Blackbody or Graybody (continuous wavebands) raytrace,
	TracePro will calculate the number of rays based on other parameters, with
	the requested number as the goal. To determine the total number of rays
	traced for thermal sources, inquire via {provide the best way to determine}.
	Large numbers of rays result in smoother and more accurate light distribu-
	tions. Large numbers of rays also take more time.
Emissivity	For a graybody specify a number from zero to 1 to indicate the emissivity. The
	number is used in the calculation of flux emitted by the surface.
Apply Button	Apply the new values in the dialog box to the surface source.

4.16	TracePro 5.0 User’s Manual