Using IES (photometric) lights
IES files (.ies) are photometry files which define the distribution of light from a light source. These files are often provided by luminaire manufacturers. By using the IES file to define your distribution, rather than one of the standard distributions available (i.e. omni-directional, diffuse, spot), you can more accurately depict your luminaire. In addition, the IES file can also be used to define the intensity of your luminaire.
Use the following steps to attach an IES file distribution to a light source:
- Create the light in the usual way.
- Right click on the light in the list and select Properties... from the menu
- Change the Light Pattern to Goniometry File
- Click the Browse... button and select the .ies file.
- Normally you will want to use the file to define the intensity of the source as well. Click the From File checkbox under Brightness to do this.
- The vast majority of IES files are known as "Type C" goniometry files. These are supported by nXt. Type A files are occasionally used by the automobile industry to define headlights, and type B files are sometimes used to define floodlighting. Type A and B are not supported in nXt.
- IES distributions already include the effects of luminaire elements such as baffles, reflectors, and diffusers. It is important to exclude these elements from the calculation by properly tagging the non-source parts of your luminaire.
- IES distributions are often assymetrical, so the process of aiming the source includes not just a target, but a rotation angle as well.