Defining Properties

Creating an Asymmetric Table BSDF Property

To create a surface property with Asymmetric Table BSDF:

1.Select Define|Edit Property Data|Surface Properties to open the Surface Property editor window.

2.Choose a catalog from the catalog dropdown list.

3.Click on Add Property. When the Enter New Surface Property dialog box is displayed as shown in Figure 3.23, select Asymmetric Table BSDF from the Scatter Model list, enter a name for your new property and values for initial angle and initial wavelength, then click OK.

4.Edit the other values simply by selecting a value and making changes.

5.Select File|Save from inside the Surface Property editor window or close the Surface Property editor and answer yes to the question “property has changed, save data?” Your new property is now available in the Property Database for future use.

FIGURE 3.23 - Selecting Asymmetric Table BSDF from the Scatter Model list in the Enter New Surface Property dialog box.

The new surface property will be displayed in a spreadsheet as shown in Figure 3.24. For this example we have chosen a Table type surface property, but you can choose any other property type that you wish.

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Surface Properties

FIGURE 3.24 - Surface Property editor created with Table Asymmetric BSDF type.

The first row for a provided incident angle (shown in the 3rd Column) provides the integrated BRDF and BTDF for this angle. The integrated BRDF and BTDF is the total scattered flux into a hemisphere from the surface normal. The rows following the integrated amount represent |β-β0| values, azimuth angles and the respective

BRDF and BTDF at these angular offsets from the specular direction. See page page 7.15 for more details about this process.

To add more |β-β0| or scatter azimuth values, click Add to open the Surface

Property – Add Data Dialog dialog box as shown in Figure 3.25. Select Scatter Beta or Scatter Azimuth, enter the value in the dialog box (the value |β-β0| = 0.01

is shown) and click OK. Like all data in the TracePro database, the data is laid out in a rectangular array. That is each time you enter a new value of Scatter Beta, TracePro fills in all the values of Scatter Azimuth for the new beta value. Conversely, when you enter a new azimuth, TracePro fills in all the beta values. Therefore if you enter M values of beta and N values of azimuth, there will be MxN rows in the table.

TracePro 5.0 User’s Manual

3.39

Defining Properties

FIGURE 3.25 - Adding a new value of |β-β0| to the BSDF table.

You can add as many Scatter Beta and Scatter Azimuth values as you wish. You may find it easier to create a template for the Asymmetric Table BSDF property and export it to a text file, fill in the BSDF values, and import the property. This is usually easier than typing in all the BSDF values in the Surface Property spreadsheet. For instructions on doing this, see the example in the Table BSDF section above.

Using an Asymmetric Table BSDF property

To use a Surface Property with Asymmetric Table BSDF, simply apply the property to a surface in the usual way. You will have to specify the orientation vectors the same way as for an Elliptical ABg BSDF Surface Property or an Elliptical Gaussian BSDF Surface Property. For more information about “Surface Properties”, see page 4.10.

3.40	TracePro 5.0 User’s Manual