keywords: sources, IES

This demo describes an alternate source shape format based on the IES (Illuminating Engineering Society) standard. It is not meant as a full lighting description (IES only has human eye relative, photometric data). Instead, only the shape of the source is read and combined with the usual source definition (see Sources1).

Summary

The scene consists of three sources shaped by an IES file description and illuminating a simple, flat surface. In order to see the shape of the source, they are placed just in front of a wall above the bottom surface and the entire setup is shown by a 45 degree slant view. The source power is arbitrary and defined using:

  • A 300W, 3000K blackbody source (brightness = 6092.78 lumens, efficacy = 20.31 lumens/Watt)

The three IES files (input as the SOURCE_SHAPE value in the accompanying material file) spread that same power by the distribution given in their file descriptions. Note that while some types of IES formats allow for different nominal pointing vectors, IES source shapes are rotated to follow the pointing input

Related Materials

The following demos, manuals and tutorials can provide additional information about the topics at the focus of this demo:

Details

A detailed description of how sources are configured is discussed in detail in the User-Defined Sources Manual. In general, a user-defined point source is a special geometric entity defined by a point in space with a pointing direction with the radiometric properties defined via a material with special "source" properties.

Important Files

This section highlights key files important to the simulation.

Important
 Documentation of a basic source definition is given in the Sources1 demo.

  • The 3 different source materials are described in the demo.mat file (see materials ies1, ies2 and ies3).

    • The IES files are given as scene relative or absolute paths

    • The provided example IES files were obtaned from the IES Library and were chosen to show a range of shapes and focusing.

Important
 Anisotropic IES shapes are supported but a convention has not been adopted for the extra degree of freedom. Setup of anistropic (non-radially symmetric) sources my require manual manipulation as a result.

Setup

The Scene Geometry

The point source array and the flat surface and wall they are illuminating are placed inthe scene via a GLIST file (see geometry/demo.glist). That GLIST file inserts the source geometry as 3 <basesource> setups.

The Sensor

A simple 480 x 240 array sensor with CIE tristimulous curves is configured and placed about 100 meters away from the scene at a 45 deg view angle.

Results

The output radiance image is displayed below. The wall behind the sources shows the general emitted shapes while the half illuminated floor gives a visualization of the light falling at a distance. The simulation should be run with a convergence threshold that is lower than the default (the image below was with a 1e-12 threshold).

demo
Figure 1. RGB image of the source array.