Sources5

keywords: sources

Summary

This demo focuses on how to setup point sources with multiple shaping coefficients, which allows the user to create more complex angular intensity patterns versus a single shaping coefficient. The scene consists of an array of point sources illuminating a flat surface. The scene has two rows containing 3 types of sources: (1) a wide beam source, (2) a narrow beam source and (3) a combination wide and narrow beam source. One row has each source illuminating the underlying flat surface horizontally. The other row has the same sources illuminating the surface from a vertical direction.

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 (in case the source has directional shaping configured) with the radiometric properties defined via a material with special "source" properties.

Important Files

For the 3 sources described via the GLIST file, there are 3 separate <basesource> entries in geometry/demo.glist
- Each entry has the same pointing vector, but the have different material labels (using 101, 102 and 103).
The sources are placed into the scene via the geometry/demo.glist file. Each source has a pair of static instances:
- One instance that places the source low and aimed horizontally.
- A second instance that places the source higher, but aimed vertically.
The 3 different source materials are described in the demo.mat file (see materials 101, 102 and 103).
- The radial power distribution is described in each material via the exponential cosine shaping coefficient. For this demo, we gave each source a unique shape coefficient.
- The spectral output of each source is described via the same Spectral Radiant Intensity File. In brief, the spectral units are in microns and the radiant intensity values are in Watts per steradian per micron.

Setup

The Scene Geometry

The point source array and flat surface they are illuminating are placed in the scene via a GLIST file (see geometry/demo.glist). That GLIST file inserts the background surface (see plate.gdb) and the 3 <basesource> setups (each has 2 instances, one aimed horizontally and one aimed vertically). The portion of the geometry/demo.glist file that defines the location and orientation of the middle source pais is shown below. The source is defined with a pointing vector aimed along the -Z axis (aka "down"). The first instance translates that source +5 meters above the background. The second instance rotates the source +90 degree about the X axis (so that it is pointed horizontally) and translates it just above the surface to that the angular pattern can be viewed on the background. This pattern of a vertical and horizontal instances is repeated for the other two sources.

Source definitions in the geometry/demo.glist file.

  <object>
    <basesource>
      <pointsource matid="wide_beam">
        <pointing><vector><x>0.0</x><y>0.0</y><z>-1.0</z></vector></pointing>
      </pointsource>
    </basesource>
    <staticinstance>
      <translation>
        <point><x>-10</x><y>+8</y><z>1</z></point>
      </translation>
    </staticinstance>
    <staticinstance enabled="false">
      <translation>
        <point><x>-10</x><y>-8</y><z>0.5</z></point>
      </translation>
      <rotation units="degrees" rotationorder="xyz">
        <cartesiantriple><x>+90</x><y>0</y><z>0</z></cartesiantriple>
      </rotation>
    </staticinstance>
  </object>

  <object>
    <basesource>
      <pointsource matid="narrow_beam">
        <pointing><vector><x>0.0</x><y>0.0</y><z>-1.0</z></vector></pointing>
      </pointsource>
    </basesource>
    <staticinstance>
      <translation>
        <point><x>0</x><y>+8</y><z>1</z></point>
      </translation>
    </staticinstance>
    <staticinstance enabled="false">
      <translation>
        <point><x>0</x><y>-8</y><z>0.5</z></point>
      </translation>
      <rotation units="degrees" rotationorder="xyz">
        <cartesiantriple><x>+90</x><y>0</y><z>0</z></cartesiantriple>
      </rotation>
    </staticinstance>
  </object>

  <object>
    <basesource>
      <pointsource matid="combo_beam">
        <pointing><vector><x>0.0</x><y>0.0</y><z>-1.0</z></vector></pointing>
      </pointsource>
    </basesource>
    <staticinstance>
      <translation>
        <point><x>+10</x><y>+8</y><z>1</z></point>
      </translation>
    </staticinstance>
    <staticinstance enabled="false">
      <translation>
        <point><x>+10</x><y>-8</y><z>0.5</z></point>
      </translation>
      <rotation units="degrees" rotationorder="xyz">
        <cartesiantriple><x>+90</x><y>0</y><z>0</z></cartesiantriple>
      </rotation>
    </staticinstance>
  </object>

The material labels for the three sources are alpha-numeric (e.g. wide_beam, narrow_beam and combo_beam) rather than purely numeric (e.g. 101, 102 and 103).

The Source Description

The source’s spatial (angular) and spectral configuration can be inspected by exploring the materials/demo.mat.

The advanced shaping options used in this demo are not supported by the graphical material editor at this time.

The Radiant Intensity filename is 300w_3000k.int
- This file has a spectral shape derived from a 3000 Kelvin blackbody curve. The total integrated power (spectrally integrated from 0.4 to 14.0 microns and angularly integrated over a sphere) is 300 Watts. The brightness is 6092.78 lumens, and the Overall Luminous Efficacy is 20.31 lumens per watt. These characteristics match up well with a standard, commercial 300 Watt tungsten incandescent light bulb.
The Normalize Shape option is enabled.
- That means the total hemispherical output of the source will remain constant regardless of the shaping parameters.
The angular shaping for the three sources is the primary difference:
- The wide_beam material uses a shape coefficent of 1.
- The narrow_beam material uses a shape coefficent of 20.
- The combo_beam material uses a shape coefficent of 1 and 20.

Radiometric descriptions of the sources in the materials/demo.mat file.

MATERIAL_ENTRY {
    ID           = wide_beam
    NAME         = Wide 300W Warm (3000K) Source
    EDITOR_COLOR = 1, 1, 1
    DOUBLE_SIDED = FALSE

    OPTICAL_DESCRIPTION = SOURCE
    INTENSITY_FILENAME  = 300w_3000k.int
    NORMALIZE_SHAPE     = TRUE
    SOURCE_SHAPE        = 1
}

MATERIAL_ENTRY {
    ID           = narrow_beam
    NAME         = Narrow 300W Warm (3000K) Source
    EDITOR_COLOR = 1, 1, 1
    DOUBLE_SIDED = FALSE

    OPTICAL_DESCRIPTION = SOURCE
    INTENSITY_FILENAME  = 300w_3000k.int
    NORMALIZE_SHAPE     = TRUE
    SOURCE_SHAPE        = 20
}

MATERIAL_ENTRY {
    ID           = combo_beam
    NAME         = Combo Wide+Narrow 300W Warm (3000K) Source
    EDITOR_COLOR = 1, 1, 1
    DOUBLE_SIDED = FALSE

    OPTICAL_DESCRIPTION = SOURCE
    INTENSITY_FILENAME  = 300w_3000k.int
    NORMALIZE_SHAPE     = TRUE
    SHAPING_LIST {
        SHAPE_MAG_PAIR =  1.0,0.2
        SHAPE_MAG_PAIR = 20.0,1.0
    }
}

The combo_beam material is the focus of this demo. Note the new SHAPING_LIST section, which includes an arbitrary set of SHAPE_MAG_PAIR lines. Each of those entries defines the shape coefficient (the cosine exponent) and the magnitude of that shape. In this case, this combo sources combines the first and second sources in the scene (using the 1 and 20 shape coefficients, respectively) into a single source. Note that the magnitude of the "wide" beam (shape = 1) is 1/5th the magnitude of the "narrow" beam (shape = 20).

Results

The output radiance image is displayed below. The top row of sources are the horizontally aimed instances and the lower row are the vertically aimed instances. Note that the combination source (right) includes both the wide and narrow shape characteristics of the previous two.

Figure 1. Pan image of the source array (gamma=3.0 scaling).