Illumination angle

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In computer graphics and geography, the illumination angle of a surface with a light source (such as the Earth's surface and the Sun) is the angle between the inward surface normal and the direction of light.[1] It can also be equivalently described as the angle between the tangent plane of the surface and another plane at right angles to the light rays.[2] This means that the illumination angle of a certain point of the Earth's surface is zero if the Sun is precisely overhead and that it is 90 degrees at sunset and at sunrise.

See also[edit]


  1. ^ Godse, A. P. (2008), Computer Graphics, Technical Publications, p. 292, ISBN 9788189411008 .
  2. ^ Hengl, Tomislav; Reuter, Hannes I. (2009), Geomorphometry: Concepts, Software, Applications, Developments in soil science, 33, Elsevier, p. 201, ISBN 9780123743459 .