CHAPTER3Learn by Doing: Analyze a Light Pipe
Menu4.Click the Trim button.A Help window is displayed, with a description of the command button. Search5.Click the X in the top right corner of the Help window to close it.6.Click the point (0, 0, 6.5) to define the section point, as prompted.
The exact coordinate is not critical, because you will change it later to try to get more rays on the target surface. A “rubber band” line is displayed, along with text showing you the length and angle of the vector leading to the second point.
7.Aim the normal vector at the lower right corner, making an angle of about -34o (the length is not critical), and then click to create the trim surface.
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MenuIf you make a mistake and trim away too much, select Edit > Undo and try again. It should look something like this:
SearchName the Object
In the System Navigator, the Trim operation has created the new object
PlanePrimitive_n (where n is an integer). This is essentially an infinite “block” that has been Boolean-subtracted from the light pipe to form the trim plane surface, which is labeled HalfPlane (this is where the surface properties reside). You can keep the default name, but it is a good idea to give important objects a descriptive name, so they are easy to recognize later. In this case, you should rename the PlanePrimitive, because you will later modify the trim angle of this 3D object. Renaming is easy.
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Menu1.In the System Navigator, right-click on PlanePrimitive_n and select Rename on the shortcut menu.
Search2.Type a new name, such as TIR_fold, and press Enter.3.Save the modified system: a.Select File > Save As.
b.Navigate to the \\LTUser (or other) directory.
c.Key in a new name, such as Tut_Lpipe_trimmed.1.lts, and click Save. Note that the file name displays in the title bar (top edge) of the 3D Design view window.
Changing Properties
Now the light is getting to the collection surface, but it doesn't fill the surface and it isn’t very uniform. This is just a rough judgment based on a small number of rays, but it's often part of the iterative design process to use a few rays to make decisions about parameters, then do a Monte Carlo simulation to predict the illumination more precisely. It may not be possible to get a great distribution with a simple TIR surface, but it's easy to experiment with the angle and position of the trim surface.1.In the System Navigator, right-click on TIR_fold (the recently renamed PlanePrimitive_n) and select Properties on the shortcut menu. The Properties dialog box gives you access to every detail of a model, and it changes, depending on the type of object selected. Right now, it displays the Coordinates tab, which applies to the entire selected object. (There is also a
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Menunavigation tree in the dialog box, which provides access to specific surfaces, but you don’t need to use it at this time.)
2.Move the Properties dialog box so that you can see the 3D Design view.
Search3.Change the Absolute values of Z and Alpha to several different values, clicking Apply each time. Can you get the ray fan to cover most of the top surface? The values shown (Z=6 and Alpha = 139o) are not necessarily optimum.
4.Close the Properties dialog box. To do this, you can click the Cancel button or the X in the top right corner.5.Click on the design view to make sure it is active.
Tip: You can also click on the name of a window in the Window Manager to bring it forward and make it active.
6.Save your modified file. This time, you can use File > Save, because you gave it a name when you saved it earlier.Tip: If the File menu is not displayed, the Properties dialog box may still be the active window. To re-display the menu bar, make the 3D Design view active.
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MenuPerforming an Illumination Analysis
Point-and-shoot ray fans are great for simple analysis and design, because they Searchinstantly show you what the light does, but eventually you will want to simulate the illumination performance, which requires several additions to the model: ????
One or more sources One or more receivers
A few decisions, such as how many rays to trace, and whether or not to display them
Various charting features, which enable you to look at analysis results
The light pipe model already has a source and receiver, but they are on a hidden layer. Next, you will display them and do some quick illumination simulations. Later examples will explain the illumination results more extensively.
Layers
LightTools models can become very complex, with optical elements, mechanical parts, rays, sources, receivers, etc. The layer feature provides a way of managing this complexity, allowing you to separate objects on as many as 32 layers, any of which can be visible or hidden. A layer number is one of the properties assigned to a LightTools object. To see or set the layer number, right-click the object’s name in the System Navigation window, select the Properties shortcut menu and click on the Display tab.
Note: Making a layer visible or hidden affects only the display of objects, not their optical behavior. For example, a mirror on a hidden layer still reflects rays. To make 3D objects “invisible” to rays, you must use another option: the Ray Traceable check box on the Ray Trace tab of the Properties dialog box.
In this model, a light source and receiver for illumination analysis have already been defined and hidden on layer 2. Follow these steps to make them visible. 1.Click on the design view.
2.Select Edit > Preferences to display the Preferences dialog box.
This dialog box controls many program parameters, with sections for General preferences, various defaults, and view-specific parameters for any views that are currently open (only the 3D Design view, in this case).
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导光柱设计指引之室内照明
