Q: Can Photopia work with AutoCAD LT?

A: You can import a 2D luminaire drawing into Photopia 2.0 and use Photopia’s 3D CAD system to build a 3D model from the drawing. Follow these steps:

1) Import the 2D drawing containing the reflector profile into Photopia with the File / Import CAD File option on the main menu. The following steps assume that the 2D geometry is constructed in the XY plane of AutoCAD LT’s coordinate system.

2) Define new layers in Photopia for 2D profiles and 3D surfaces for the various luminaire components, i.e. Profile-Main, Refl-Main, Profile-Lens, Tran-Lens, etc. The layers dialog is found under Settings / Layers on the main menu.

3) Delete extraneous geometry so that only the essential geometry remains that is required to make the 3D surfaces of the various luminaire parts, i.e. lines or polylines describing the reflector profile, lens profile and lamp holder locations. This is not required, just a suggestion to clean up the drawing.

4) Change the properties of the 2D entities so that they reside on the appropriate layers just created, i.e. put the main reflector profile on layer Profile-Main. This can be done by selecting the geometry in the CAD view and choosing the new layer in the property control on the right side of the screen. Note that several entities can be picked together and their layer changed at the same time.

5) Move the entities (lines, arcs, etc.) that comprise the 2D profiles of the luminaire components so that the center of the luminaire opening is located at (0,0,0) in Photopia’s World Coordinate System (WCS).

6) Rotate the 2D profiles of the luminaire components so that the reflector opening is oriented toward the –Y axis if the luminaire produces downward directed light or toward the +Y axis if the luminaire produces upward directed light. The rotate command is under Modify / Rotate on the main menu.

7) Change the view to an isometric view that allows the geometry to be seen in 3D. Right click your mouse in the CAD view and select Standard Views / Isometric View from the pop-up menu.

8) Now the 2D profiles need to be rotated about the world X-axis by +90° in order to put the profiles in the Front View, which is the world XZ plane. Until Photopia gets a 3D rotate command, we need to use the standard rotate command that always rotates about the Z-axis. But since this is the Z axis of the current coordinate system, then in order to rotate about the world X-axis you need for first set the Construction Plane (cplane) to the Right Side View. This is done by selecting Settings / Construction Plane from the main menu, then entering “O” for Ortho and then “R” for Right Side View. You will see the cplane axes change their orientation in the 3D CAD view. Now select Modify Rotate from the main menu and rotate the 2D geometry +90° about 0,0,0.

9) If the reflector is comprised of linear extrusions, then you will use the Extrude command to make the 3D surface. First make the appropriate 3D geometry layer current, for example Refl-Main, so that the new polyline mesh created by the Extrude command will be created on the appropriate layer. Select Settings / Layers and then pick the layer and click the Set Current button in the Layers dialog. Then select Draw / Extruded Surface from the main menu to run the extrude command. You will be prompted for an extrusion length, and it will center this length about the location of the original 2D profile. Note that all Arc entities will be subdivided along their profile according to the “U” setting (this is half of the UV resolution typically associated with meshes). Select Settings / Set U from the main menu. Also note that you can select as many entities as you like to extrude at the same time.

10) If the reflector is comprised of circular components, then you will use the Revolve command. The Revolve command either uses a Line entity as an axis of revolution or you can choose to revolve around the X or Y-axis going through an arbitrary point. So if you simply want to revolve around the cplane Y-axis, then you pick “Y” when prompted and then choose (0,0) as the translation point locating the Y axis. The revolved surface will have an azimuthal resolution defined by the “U” setting. Note, all Arc entities will be subdivided along their profile according to the “V” setting. Then make the appropriate 3D geometry layer current, for example Refl-Main, so that the new polyline mesh created by the Revolve command will be created on the appropriate layer. Once you are ready to revolve the reflector, select Draw / Revolved Surface from the main menu.

11) If the reflector is a linear extrusion, then construct the end plates. This can be done in a variety of ways, but one easy way is to draw a horizontal line of the appropriate width through the middle of the reflector at the same location as the original 2D profiles. Then put the cplane back to world coordinates. Then extrude this horizontal line the appropriate height to cover the end of the luminaire. You can then move the end piece to one of the ends of the reflector and then copy it to the other end.

12) Import the appropriate lamp model for the design by selecting File / Import Lamp. You can specify several lamp locations at the command line. Press Enter at the prompt when done. You can rotate, move or copy the lamps as required so that they are placed correctly within the luminaire.

13) Now the luminaire is ready to be analyzed by following the same process as described in the tutorials in Chapter 3 of the User’s Guide.