Luminaire

[Alfie58]

Looking for a tip as to whether it is possible to generate a luminaire of a particular shape - rather than a point, as provided by the 'add luminaire' facility. I'm particularly looking to use LUMOS to view a room illuminated by fluorescent tubes.

[Frudawski]

LUMOS uses the geometry data that is provided in the .ldt (EULUMDAT) files. So, if you switch to another luminous intensity distribution (EULUMDAT file) the geometry of the luminaire should change accordingly. You can edit the .ldt (EULUMDAT) file yourself with a text editor, lines 13-15 are relevant for the geometry.

See: https://docs.agi32.com/PhotometricToolbox/Content/Open_Tool/eulumdat_file_format.htm

[Alfie58]

Hi, I've figured out the EULUMDAT files needed and can load these. Thanks for your help. Can I save myself some effort by asking you if the coordinates of the object (as opposed to the luminaire), which is currently set as a cube, is imported from a file or defined in the code? I'm looking to add a complex shaped object from a file. Also, are there restrictions on the complexity of the object (maybe resulting from the radiosity calculation)? I am trying to get to grips with the code but I'm not an expert.

[Frudawski]

You can create complex objects by combining simple objects, here are some hints how to handle objects:

1. Go to the object tab, a list of all objects will appear. In the table one can adjust the relative coordinates of each object inside the room geometry and also rotate them.

2. By selecting any object from the list one can edit the object in the table. Using a right click in the table, one can add or remove additional points.

3. In the material tab one can assign the desired materials.

4. Back in the object tab, there is a „group tool“ in the toolbar, which allows to group or ungroup any objects.

5. Also in the object tab, there is an „export tool“ in the toolbar which allows to save any (also grouped) object.

6. In any other LUMOS project one can now import the saved object with the „import tool“ in the toolbar.

[Alfie58]

Thanks. I have a grouped set of four parallel fluorescent tube luminaires near the wall of a room. I've selected white walls and, just as a start, selected red brick as the spectrum of the tubes (ok - it's just because I don't have the spectrum I need just yet). It all seems to work and generates a rendered image - which looks plausible - but I get a pile of error messages that I can't seem to figure:-

'Warning: Duplicate data points have been detected and removed - corresponding values have been
averaged.

In hyperspecfisheye (line 299)
In surfaces_radiosity_calculation (line 1375)
In spec_simulation>uitoggletool17_ClickedCallback (line 5973)
In gui_mainfcn (line 95)
In spec_simulation (line 42)
In matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)spec_simulation('uitoggletool17_ClickedCallback',hObject,eventdata,guidata(hObject))
In plotGouraud (line 507)
In spec_simulation>simulation_listbox_callback (line 4586)
In spec_simulation>simulation_tab_Callback (line 6662)
In gui_mainfcn (line 95)
In spec_simulation (line 42)
In matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)spec_simulation('simulation_tab_Callback',hObject,eventdata,guidata(hObject))
Calcualtion time: 42 s

'

will keep working on this. But one of your useful tips might save me time.
Thanks.

[Frudawski]

The warning appears during the triangulation for the mesh generation when datapoints are doubled or are very close to each other. MATLAB automatically remove these points but will show one (or more) warning message(s) during the simulation. You can ignore this warning. I will try to remove this issue in future, but since it does not affect the functionality, it is not on the top of my todo list.

[Alfie58]

Thanks for that.
I have successfully used LUMOS to render lighting in a room with a horizontally mounted 1.8m fluorescent luminaire. The lamp shows up in position on the pre-simulation 3D plot and I get some sort of rendering that looks reasonable and that also shows the luminaire in position. The problem I am interested in is a vertically-mounted 1.8m luminaire (actually an array of these in a hexagonal room). I note the resulting simulated rendering 3D plot for a single luminaire no longer shows the luminaire. But if I place the laminar at, say 45 degrees, it shows up. Not a major issue. You may have a comment. [Appreciate that you can't be dealing will all user applications - so feel free to ignore, of course]. Maybe these plots illustrate the issue:-

[Alfie58]

what format is the imported object expected to be? .stl ? Will get there in the end! Thanks.

[Frudawski]

Concerning the disappearing luminaire: LUMOS is not good at dealing with co-planar objects, meaning that if the luminaire is exactly (or numerical close) to the wall, it might be treated as outside the room geometry. That could result in the described behavior. In general, it is better to place luminaires a few mm's or cm's inside the room geometry to be on the save side. If that does not help, fell free to upload an example with the issue and a can take a look into it.

LUMOS does only work with LUMOS created objects, no support for external created object so far. Since the calculation time does increase dramatically with geometric complexity, I don't think I will add that feature.

[Alfie58]

I have a Eulumdat file for a 2m fluorescent tube - emitting along its length in all directions. I note, however, the output appears to emanate from just a point on the length of the tube. I can test this by placing it close to a wall in a range of orientations. Any advice as to whether this an issue with my Eulumdat file or with my incorrect use of LUMOS?

[Alfie58]

Hi, wondering if you have any advice on the use of a Eulumdat file for a bare 2m fluorescent tube in LUMOS (as above). Will LUMOS treat the tube as an emitter along its length in all directions? Bit stuck on this - any advice most welcome. Thank you.

[Frudawski]

Sorry, your first question somewhat escaped my attention.

EULUMDAT files are measured as point light sources and are mostly treated as that. To avoid simulation errors in situations as described, one can divide the luminaire in smaller sections in the simulation, e.g. ten segments with 20 cm length, with the measured luminous intensity distribution but a tenth's of the luminous flux. Like other lighting simulation programs, LUMOS should do that automatically to some degree.

The threshold in LUMOS for dividing a luminaire into smaller sections is: distance luminaire-to-patch / luminaire's longest side < 5. If you upload an example, I could check if there is an error in the automatic luminaire subdivision. Or you divide your luminaire manually into smaller segments and adjust the luminous flux accordingly.

[Alfie58]

[If you have time - maybe you can check over these and see if you can spot a problem.

Tony Test Tubular Fluorescent Lamp - Mirrored.txt](https://github.com/Frudawski/LUMOS/files/12343570/Tony.Test.Tubular.Fluorescent.Lamp.-.Mirrored.txt)

[Frudawski]

Thank you for the example file. I found a bug in the luminaire subdivision, which I was able to fix. If the luminaire was rotated, as in your case, the automatic subdivision was not working reliable.

Please get the new LUMOS version 1.09 from the repository, your simulation should then look something like this:

[Alfie58]

thanks so much for correcting this so quickly. I had a quick go this morning but failed to get the you, obviously correct, rendered distribution. I may have messed up installation of 1.09 (although I don't think so). Perhaps if you let me know the function and a line in the code you changed in 1.09 it would help confirm if I have the latest version. Don't worry tho if time pressed. I will work on it..

[Frudawski]

Make sure you add the luminaire's dimension to your EULUMDAT file, what seems to be the case in two of your example plots. In your example EULUMDAT file, the lines 13-15 were blank though, I had to add those manually since LUMOS gets the luminaire dimensions from the EULUMDAT file. Maybe you forgot this in your quick test?

Just in case, the link to the EULUMDAT file format explanation:
https://docs.agi32.com/PhotometricToolbox/Content/Open_Tool/eulumdat_file_format.htm

Otherwise, the lines 651+ in surfaces_radiosity_calculation.m should now look like this in version 1.09:

            % luminaire max dimension
            lumrotM = rotMatrix(luminaires{lum}.rotation);
            dim = max(diff(luminaires{lum}.geometry{1}));
            lumdim = dim(1:3)*lumrotM;
            mdim = max(dim(1:3));

But that is not the only change I had to make.