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← Introduction to Transparency - Interactive 3D Graphics

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

  1. Up to this point, we've been working with opaque materials. Where light hits the
  2. surface, and bounces off. For a number of reasons, transparent objects are more
  3. challenging. First, light refracts, and so changes its direction when it hits a
  4. transparent surface. For example, here light comes from the surface of the
  5. pencil, travels through water, and hits the glass. The glass causes the light to
  6. go in a different direction. Such the different light rays reach our eyes and
  7. cause the pencil to look bent. This change in direction can also affect the
  8. distribution of light on a surface. This crystal ball acts similarly to a lens,
  9. focusing the light and creating various bright spots below it. In computer
  10. graphics, we call these bright spots caustics. The color and the intensity of
  11. the light can be filtered by the transparent object. The farther a ray of light
  12. travels through an object, the more light that can be absorbed. Even thin
  13. filters can change the color of the light. All of these effects can be simulated
  14. or at least approximated in a convincing way. Refraction where the light changes
  15. direction is expensive to do correctly. I'll be discussing it further in later
  16. lessons. It's also possible to computer the amount of light absorbed due to
  17. traveling through an object, though this can be costly. In the following
  18. lessons, I'm going to focus on absorption of light by thin transparent surfaces,
  19. such as these eyeglass filters. To simplify further still, I'll be talking about
  20. only the effect of such filters on objects visible through them. In other words,
  21. I won't be talking about how light passes through such a filter, reaches another
  22. surface, and then travels to the eye. I'll only be talking about light that
  23. travels from the object through the filter. This all sounds like a lot of
  24. simplification, but you can get wonderful effects from just this form of
  25. filtering alone. For example, this fantastic demo made by Alexander Roddick
  26. shows how transparency can be used to effect. There are other cool effects going
  27. on here, such as the God rays of light. But transparency is what really makes
  28. this demo shine. It's 1 of my favorite Web GL programs. .