Creating a Surface Source

The Surface Source models the light emission of a source taking into account its physical properties as the flux, the spectrum, the emittance and the intensity.

To create a Surface Source:

Important: In case you want to add the source in a Direct simulation, make sure that all parts of the source are enclosed in one single body, or in one ambient material, and therefore are not located in two (or more) bodies or ambient materials. Otherwise you may generate propagation errors.
  1. From the Light Simulation tab, click Surface .
  2. In the 3D view, click , select the exitance/emissive faces and click to validate.
    Note: The selection of faces from an imported *.obj file is not compatible with the Surface Source.
    The face(s) appear in the Emissive faces list. A preview of the ray's distribution and color appears in the 3D view.

    If you need to adjust the ray's propagation direction, check Reverse normal.

  3. According to the flux you want to define, from the Type drop-down list:
    • Select Luminous Flux (lm) and define its value in lumens.
    • Select Radiant Flux (W) and define its value in watts.
    • Select Luminous Intensity (cd) and define its value in candelas.
  4. In the Exitance section:
    • Leave the Variable exitance set to False to have a constant ray energy over the source.

    • Set the Variable exitance to True to have a variable ray energy over the source depending on the xmp energy distribution.
  5. If you set the Variable exitance to True:
    1. From the File drop-down list, click Browse and select a *.xmp file.

      If you want to see the file properties or edit the xmp map, click the file's drop-down list and click Open file.

      If you need to adjust the ray's propagation direction, set Reverse direction to True.

    2. In the 3D view, set the Axis System of the file by clicking to select one point for the origin, to select a line for the X axis, to select a line for the Y axis or click and select a coordinate system to autofill the Axis System.

      If you need to adjust the axes orientation, use Reverse direction.

      Note: If you define manually one axis only, the other axis is automatically (and randomly) calculated by Speos in the 3D view. However, the other axis in the Definition panel may not correspond to the axis in the 3D view. Please refer to the axis in the 3D view.
    Note: If you selected a spectral map, you cannot set another spectrum.

    If you selected a non-spectral map, you need to specify a spectrum type.

  6. In the Intensity section, set the intensity distribution of the light source. From the Type drop-down list:

    • Select Lambertian for a uniform distribution and set the Total angle of the surface source's emission.

      Note: By default Total angle is set to 180° so that the source emits on a hemisphere.


    • Select Cos for a distribution that follows a cosine law at nth order and set the N order of the cosine and the Total Angle of the source emission.



    • Select Symmetric Gaussian and set the FWHM Angle and the Total Angle of the source emission.

      FWHM Angle has the same value for X and Y and is computed on both axes.



    • Select Asymmetric Gaussian if you want to define different FWHM values on X and Y:
      • Set the Total Angle of the source emission.
      • Set the FWHM angle for X and Y.

      • In the 3D view, click to select a line for the X axis, and to select a line for the Y axis or click and select a coordinate system to autofill the Axis System.

        Note: If you define manually one axis only, the other axis is automatically (and randomly) calculated by Speos in the 3D view. However, the other axis in the Definition panel may not correspond to the axis in the 3D view. Please refer to the axis in the 3D view.


    • Select Library and click Browse to load an intensity file (*.ies, *.ldt, *.xmp).

      If you want to see the file properties, click Open file to open the IESNA Viewer.

      If you want to inherit the flux value from the intensity file, in the Flux section, set From intensity file field to True.

  7. If you selected Library, set the orientation of the source intensity distribution:
    • select Axis system, and in the 3D view set the orientation of the intensity distribution by clicking to select a line for the X axis, and to select a line for the Y axis or click and select a coordinate system to autofill the Axis System.

    • select Normal to surface to define the intensity distribution as normal to the selected surface.

    • select Normal to UV map to define the intensity distribution as normal to the selected emissive surface and its orientation on the emissive surface.

      Normal to UV map is particularly useful in case of an asymmetrical intensity distribution as it allows you to define accurately its orientation on the surface.

      Note: When Normal to UV map is used, the intensity distribution preview is defined as Normal to Surface due to performance issue.
      Important: For the Normal to UV map to work you need to create a Texture Mapping on the emitting face:
      1. Create a UV map to apply on the emitting face of the surface source.
      2. Create and apply a FOP or a SOP material with Use Texture set to True on the emitting face.

      3. As Use Texture is activated, define at least one Surface Layer with a Texture Image on the emitting face.

        Any image is appropriate. The image is required only to consider the UV map on the surface.

      4. In the Simulation options (Interactive, Direct, Inverse), in the Geometry tab, check Texture.
  8. If you selected Library, you can select exit geometries so that rays are propagated from these geometries. In the 3D view, click , select the exit geometries and click to validate.
  9. In the Spectrum section, from the Type drop-down list:
    • Select Monochromatic and specify the unique wavelength in nanometers.

    • Select Blackbody to set the temperature of the source in kelvins.

    • Select Library and from the drop-down list click Browse to load a *.spectrum file.

      If you want to see the file properties or edit the file, click Open file to open the Spectrum Editor.

      Note: If you select a XMP map with spectral conoscopic intensity, the spectral information of the map is displayed in the Spectrum group box.
  10. In Optional or advanced settings :
    • Adjust the Number of rays to display in the 3D view.
    • If needed, adjust the Length of rays to display in the 3D view.
    • If you selected an intensity distribution file, set Display intensity diagram to True to display the intensity diagram in the 3D view.
    • If you want the source to flicker, browse and select a Flux variation file, and add if necessary a Relative lag.
    For more information on the Timeline parameters, refer to Understanding the Surface Source Parameters.
  11. If you are using a variable exitance, click Compute to apply the XMP file to the surface source.
The Surface Source is created and should appear in the 3D view and in the Simulation panel.