AutoCAD 2008

I have metioned there are lots of changes in the Render Module in Autocad 2008 in my previous articles. One of this changes is photometric lights. Actually photometer is a comprehensive science division. However, we are not going to study it in detail. Briefly, it is a science field that investigates the transmittance, intensity etc. values of light during its travel from the source to the objects in real world. This corresponds to realistic lights in AutoCAD. You can see a render example formed by photometric light sources in Figure 1.

Fig.1

Firstly, we have to set the LIGHTINGUNITS system variable to 1 ( international ) in order to use photometric lights. Later, you can add lights manually if you are confident enough or you can use pre-defined photometric lights. In this part of series of articles, I am going to explain adding lights manually.

1 – Adding Photometric Lights Manually: It is a complicated process to add photometric lights manually. Through this process, we need .ies file that stores the characteristics of our light source. Light source producers publish graphs of light transmittance network for their products. These graphs are similar to the one in Figure 2.
These graphs are in IES format and have to meet the requirements of LM-63-1991. IES files are published by some of the light source producers. A large .ies files library can be accessed via the web site of Paramount Industries. Through world wide web other firms can be accessed by professionals. Two kinds of photometric light can be added to the stage; WEBLIGHT as a directed light source or FREEWEB as a point light source.

Fig.2

WEBLIGHT: We can quit from the command after setting the direction of the light. Further options can be changed from ‘properties ‘ window ( Figure 3). As can be seen, the intensity and color options (as candela) of the light can be changed in photometric properties section. Detailed pop-up windows are gioing to appear when these properties are accessed. Firstly, let us take a look at the light intensity option ( Figure 4 ).

Fig.3

Command : WEBLIGHT
Specify source location <0,0,0>: 10,10,280
Specify target location <0,0,-10>: 10,10,0
Enter an option to change [Name/Intensity factor/Status/Photometry/weB/shadoW/filterColor/eXit] <eXit>: x

Fig.4

You can adjust the intensity of the light in any desired unit in this window. Color of the light can be adjusted via the window opened by a small command icon when you get the relevant line (Figure 5).

Fig.5

I chose a mercury-streamed light for you to better understand the color and temperature values. The important point starts when the photometric network is being prepared ( Figure 6 ).

Fig.6

Browse a .ies file downloaded from internet and the transmittance graph is ready. A corner light source is given in the example.

FREEWEB: The only difference of the point light source is the question for the source location only. Target point is not being asked since it is not a directed light. Other properties are the same.

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AutoCAD 2008, Render