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MenuTip: You can go directly to the Preferences dialog box for the active design view Searchby choosing View > View Preferences or by right-clicking in the design view and selecting View Preferences on the shortcut menu.3.In the navigation tree of the dialog box, click the plus sign (+) next to the View Preferences heading, and then click on the name of the 3D Design view below it.4.Click on the Layers tab to bring it to the front.

5.Click the check box for layer 2 (Lum_Objects) to make it visible.

6.Click OK.

Clicking OK applies changes and closes the dialog box.

The source and receiver symbols are now visible in the 3D Design view.

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MenuSources and Receivers

This section briefly describes sources and receivers. Please see the LightTools Illumination Module User’s Guide, Chapter2 and Chapter3 for detailed information about these types of objects.

Sources. LightTools supports a variety of sources, from point sources to surface or volume emitters, in simple shapes to detailed lamp models made up of multiple sources and mechanical parts. You can also use simple sources with angular and spatial distributions (apodization files) applied to match measured or desired distributions, as well as ray data sources created from measurements of real sources.

Receivers. Receivers are special objects created to collect ray trace data for illumination calculations. LightTools supports spatial and angular receivers, and they are usually attached to a surface of an object. (A far-field angular receiver is not attached to any object.) Receivers assign ray energy (weighted ray data) to bins (cells) in a collection mesh, and this allows the irradiance and other properties to be determined. There is a trade-off between radiometric accuracy (based on the number of rays per bin) and spatial accuracy (based on the number of bins across the receiver). LightTools allows you to re-bin the data without re-tracing the rays. In this sample model, a source and surface receiver are already defined. The source is a 1.0 watt point source with an apodization file attached to simulate the Gaussian intensity of an LED. The receiver is attached to the rectangular dummy element (named AirLens in this model, because that's its material) defined for this purpose. You can attach receivers to surfaces of real objects or to dummy elements, depending on your goals.

SearchSimulation Info and Ray Preview

A Monte Carlo simulation requires a large number of samples for accurate statistical estimates of illumination. Samples in LightTools are traced rays, but unlike point-and-shoot rays, rays in an illumination simulation are traced in random directions from randomly selected points in or on the defined sources. Apodization and other factors affect the selection of random points so source behavior can be accurately simulated.

Before tracing large numbers of Monte Carlo rays, it’s a good idea to trace a

smaller number with the Show Preview option turned on. When Show Preview is on, LightTools draws the rays in the design view, allowing you to see whether or not things are working correctly. Drawing many rays may slow down the ray trace, so it makes sense to keep the value for this option low or turn it off when you’re tracing thousands of rays (or more).

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Menu1.Select Ray Trace > Simulation Input to display the Simulation Input dialog box.2.Change the Total Rays to Trace to 200 and click Apply.

3.Check the box next to the option Show Preview and enter 200 Rays.4.Click Apply, then OK.

SearchNo rays are traced yet. You have just defined the parameters for the simulation.You can run the simulation from the Ray Trace menu or from the toolbar.5.Click the Begin All Simulations button or select Ray Trace > Begin All Simulations to trace and display the rays.Your 3D Design view should look something like the following figure. (The design view has been rotated in this example.)

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MenuSearchUnderstanding Charts

When you run a simulation, all of the output data is stored in memory; you see the results when you open an illumination chart. Because there are many ways to view and analyze illumination results, the best chart to display depends on your goals. In this example, you will look only at the illuminance (spatial) distribution on the predefined surface receiver. Other available analyses and charts (including the interactive LumViewer) will be discussed in later examples.

Note: The menus always use the term illuminance, although, strictly speaking, this term applies only when photometric units are in use. In this example, the spatial distribution is in radiometric units of watts/mm2.

Scatter charts are always a good starting point, because they are the closest thing to a view of the raw ray data. They don't tell you anything about the energy or

statistics, but they allow you to see how completely you have covered the receiver.1.With the 3D Design view active, select Analysis > Illuminance Display > Scatter Chart.With only 200 rays for preview, the scatter chart is not very dense, but it can help you understand the relationship between chart coordinates and system coordinates. In the figure below, the 3D Design view has been rotated so that the receiver surface has the same orientation as the chart. You can see that the

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Menuscatter chart is a kind of “ray diagram,” showing where the rays fall on the receiver surface.

SearchTip: Chart coordinates are receiver coordinates. If you are not sure of the

relationship between the chart coordinates and what you see in the design view, you can attach a local coordinate system to the surface holding the receiver. This was done in the figure above.

To attach a local coordinate system, click the UCSOnSurface toolbar button, shown at left, and then click on the receiver surface. (UCS means user coordinate system. This is also the rotation point for right-mouse view operations.)

A local coordinate system diagram is displayed on the surface. To return the UCS to the global origin, click the UCSToGLobalOrigin toolbar button, shown at left.

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