Creating a U.S. Standard Atmosphere 1976 Source

The U.S Standard Atmosphere 1976 source allows you to generate light from the sky according to a time and location. With this source, signals can be collected outside the visible spectrum including in the infrared.

To create a U.S. Standard Atmosphere Ambient Source:

  1. From the Light Simulation tab, click Ambient and click U.S. Standard Atmosphere 1976 .
    A preview of the sun and the 4 cardinal points appear in the 3D view. The sun's position is computed according to the timezone and location set.
  2. In the 3D view:
    • If you want to modify the Zenith direction, click and select a line (normal to the ground).
    • If you want to modify the North direction, click and select a line collinear to north direction.
    • or click and select a coordinate system to autofill the Axis System.
    Note: The North direction corresponds to the rotation axis of the earth projected on the ground.
    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.
  3. From the Sun type drop-down list:
    • Select Automatic to automatically calculate the sun position according to the north direction and the selected Timezone and location.
    • Select Manual to manually set the Sun direction by clicking a line in the 3D view or by using the 3D view manipulators.
  4. Set the Time zone and location:
    • If you want to set the coordinates manually (longitude and latitude), from the Location drop-down list, select User.
    • If you want to use the night sky model, adjust the Date and time.
  5. In Optional or advanced settings , adjust the size of the rays displayed in the 3D view.
The Ambient Source appears in the Simulation panel. Four cardinal points and a representation of the sun are displayed are displayed in the 3D view.