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Viewshed

Viewshed analysis is used to visualise visibility from a specified point of view with a perspective projection. Think of it as a way to visualise what would be visible from a camera. It is defined in the scene view settings by ViewshedSettings by:

  • A position for the viewpoint.
  • An orientation (using bearing and tilt).
  • What colors are applied to the visible and hidden parts of the scene.
  • The horizontal field of view and aspect ratio which define the shape of the view cone.
  • The max distance which is how far the view cone goes, and the start factor which gives how close to the maximum distance we start the view cone: 0 is at the viewpoint and 1 is at the max distance. For instance with a maximum distance of 1000m and a start factor of 0.25, the view cone would see objects starting 250m away from the camera, and up to 1000m away.

Additionally a wireframe can be drawn to help with visualising the viewshed volume. It respects the start and max_distance property values by defaults, and therefore outlines a truncated pyramid shape (because the start value must be greater than 0). However the draw_wireframe_from_position property can be set to make the lines reach the viewpoint position.