Issue
What is the best 3D object type to use in AutoCAD for shadow casting?
Solution
AutoLUX currently recognizes two types of AutoCAD geometry as obstructions – 3D solids and linear objects with a thickness. The simplest method is a line, arc or polyline with a thickness because it speeds up processing time but gives slightly less accurate results. 3D Solids give more accurate results, but these take longer to process, and slightly longer to create. So, it is a case of weighing up and balancing accuracy against performance.
Method 1 – giving a linear object a thickness
If you have on open polyline, you will need to close this first before creating your extrusion. Note that the extruded object replaces the polyline so you may wish to copy this so you can retain the original. You can then create the extrusion to the building (or other object) height to get the 3D Solid obstruction. Simply set the thickness property of your linear object using the Object Properties Manager palette to the object or building’s height.
Method 2 – creating a 3D solid form a linear object using the EXTRUDE command
The best way to create a 3D shape is to use the AutoCAD EXTRUDE command on a line, arc or polyline. Please note, however, that if you extrude a polyline that is not closed, then your resulting geometry is a Surface (Extrusion). AutoLUX currently does not recognize Surface (Extrusions) as an obstruction. Therefore, these are ignored in the calculations, it calculates as if there was no obstruction at all.
Command: PEDIT
Select polyline or [Multiple]:
Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype gen/Reverse/Undo]: c
Enter an option [Open/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype gen/Reverse/Undo]:
Command: EXTRUDE
Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid
Select objects to extrude or [MOde]: 1 found
Select objects to extrude or [MOde]:
Specify height of extrusion or [Direction/Path/Taper angle/Expression]: 10