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← Directional Lights - Interactive 3D Graphics

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Showing Revision 2 created 05/25/2016 by Udacity Robot.

  1. Light emitters can take whatever form you like since, ultimately, the effect of
  2. a light is something computed in the vertex or fragment shading. That said,
  3. there are a few different common forms of lights used in applications. The
  4. simplest is called a directional light. This type of light is defined by just
  5. that, a direction vector. A directional light is something like the sun. The
  6. direction to the sun is essentially the same for every object on earth, and a
  7. directional light is considered infinitely far away. In many modelers, such as
  8. the 3JS editor here, the directional light will be shown as some local point
  9. that you can move around. However, you're truly manipulating the direction, not
  10. the location of the light. Since we often combine colors in various ways,
  11. there's not necessarily an upper limit of 1.0 to a color channel. It all
  12. depends. For example, if I want a clear the screen, I would want to use values
  13. from zero to one. There's an upper limit of each channel's intensity, so values
  14. larger than 1.0 are beyond the monitor's abilities. However, if I wanted to
  15. make the light bright, I might set its intensity to 11. When the distance from
  16. the light to the object and the object's color are taken into account, the
  17. final color may well be within the zero to one range. In some systems, you can
  18. even set the light intensity to a negative number, meaning the light is somehow
  19. sucking photons from the surface. The light's color is just a number in an
  20. equation after all. This is true for a material's color too, that it could be
  21. set however you want, but we tend to leave material colors between zero and
  22. one, thinking of them as reflectivities. These basic illumination equations are
  23. not based on any physical unit, such as watts or lumens, but rather are set in
  24. the zero to one range for our convenience.