CHAPTER 4	Applying Properties

Using Properties

After the geometry has been created in TracePro, properties are assigned to the geometry determining how rays interact with the model and how it is displayed in the Model Window. TracePro includes the capability for you to define your own properties (see Chapter 3, “Defining Properties”).

Limitations in Pre-Defined Property Data

Much of the property data supplied with TracePro is derived from data sheets and published data. In some cases the data is very complete as is the case with optical glass data from manufacturers like Schott, Ohara and Hoya. In other cases the data is only given for a small range of values, which is the case for the metal properties from manufacturers like Alonad and Sacall. For example aluminium suppliers declare specular reflection and diffuse reflection in accordance with DIN 5036, a method of measurement which use an integrating sphere. This is insufficient to describe the BSDF distribution function necessary to simulate scatter in TracePro. It is recommended that each user verily that the data is appropriate for their needs and that measured data be obtained directly from the material vendor or a third party measurement service. This is particularly important for scatter data and optical coatings.

Applying Property Data

Which properties are needed to model a specific problem? To answer this question, it is useful to think of the properties in terms of Physical Properties vs. Raytrace Properties.

Physical Properties translate into the hardware that is built when the model or design is completed. These properties have a direct impact on the ray trace since include Material and Surface properties. The list of Physical Properties in

Table 4.1 can be reviewed to determine which properties are applicable to a given model.

Raytrace Properties are applied to utilize features available in TracePro to assist you in making the ray trace more efficient. These properties are not physical attributes of the final hardware. Importance Sampling and Exit Surface are examples of ray trace properties. It is not necessary to apply any of these properties to a given model. Once the Physical Properties have been applied, you can move ahead to Chapter 5, “Ray Tracing” to determine which TracePro Raytrace features will be useful for the model, and then come back to this chapter to apply the necessary ray trace properties.

The method for applying properties is the same for all properties. The only distinction is between properties that are applied to Objects vs. those applied to Surfaces. See Table 4.1 for a summary. The steps for adding properties are:

•Select Define|Apply Properties from the menu to open the Apply Properties dialog box. A right click in either the System Tree or the Model Window

Applying Properties

provides a shortcut to the Properties dialog box. See “Context Sensitive Menus” on page 1.8.

•Select the appropriate tab within the Apply Properties box for the property to be updated.

•Select the object or surface, either by selecting it in the System Tree or in the Model Window. See “Selecting Objects, Surfaces and Edges” on page 1.10.

•Input the necessary data into the Apply Properties dialog (see the remainder of this chapter for specific information about each property)

•Click the Apply button.

•To confirm that a property has been applied, expand the object or surface in the System Tree and review the property information.

•The Apply Properties dialog is a modeless dialog, so it can be left open while doing other things in TracePro. At any time, you can come back to the open Apply Properties dialog, select an Object or Surface in the System Tree, input the necessary data and click Apply.

•Surface Properties may be applied to individual surfaces or to objects. If the property is being applied to a selected object each of the object’s surfaces will receive the property data. This may be a useful shortcut. Be careful to select the desired set of objects and surfaces when applying property data.

TABLE 4.1. Apply Properties Categories

		Object	Surface
		Material*	Surface*
		Temperature	Surface Source*
	Physical Properties	Mueller Matrix*	Diffraction
		(polarization)	Temperature
		Gradient Index*	Temperature Distribution
		Bulk Scattering*	RepTile**
	Raytrace Properties	Raytrace Flag	Surface Source
		Importance Sampling	Prescription
			Importance Sampling
			Exit Surface
	Other Properties	Color	Color
		Class and User Data

* Properties must exist in the Property Database to be used. A number of properties are predefined for your use, but you may define new ones (See Chapter 3).

Expert ** RepTile Properties must be defined prior to use and are stored in the Property Database (See “RepTile Surfaces” on page 3.45.).

To provide additional perspective on the Apply Properties tools discussed in this chapter, Table 4.2 lists the properties and the purposes for which they are used.

4.2	TracePro 5.0 User’s Manual

		Using Properties
	TABLE 4.2. Properties and Applications
	Properties	When Needed?
	Material	Refraction, Fresnel Reflections, Bulk Absorption, Bulk Scattering,
		Gradient Index
	Surface	Reflection (other than Fresnel reflection), Coatings, Thin Film
		Stacks, Scatter, Surface Absorption, Gratings
	Surface Source	Used to define source for Surface Ray Tracing. See Chapter 5,
		“Ray Tracing”.
	Temperature	Needed only if other properties are temperature-dependent, such as
		cases where the Index of Refraction varies with temperature
	Mueller Matrix	Needed only when modeling Polarization effects
	Gradient Index	Needed only for materials with varying Indexes of Refraction,
		requires Material property
	Bulk Scattering	Needed only for modeling scatter from within the volume of an
		object, requires Material property (For Surface Scatter, see “Surface
		Properties” on page 4.10)
	Fluorescence	Used to simulate models with fluorescent material.
	Diffraction	Needed only when the diffraction effects of rays incident near the
		edges of an aperture are significant, usually for stray light analysis
	Color	To change the display color of an object or surface to another color
		from the default color (green)
	Class & User Data	Provides resources that the macro language can use
	Raytrace Flag	To let a user remove individual objects from a raytrace
	Prescription	Needed for Auto Importance Sampling and optical scatter intercept
		limits
	Importance Sampling	Needed only for Importance Sampling
	Exit Surface	Needed for Simulation Mode raytraces and Reverse Ray Tracing
	RepTile	Needed for modeling surfaces with repeated structures
	Temperature Distribution	Used to apply spatially varying temperature distributions to sur-
		faces, requires Surface property

TracePro 5.0 User’s Manual

4.3