Coherence and its types in visible surface algorithms

Coherence is the degree to which parts of an environment exhibit similarities in depth, color and texture. Types of coherence:

  1. Object coherence: In this type of coherence the comparison is done only on the objects in question.
  2. Face coherence: To do face coherence calculations are done for one part of face with changes to other part of face.
  3. Edge coherence: In this coherence two edges are compared with one another.
  4. Implied edge coherence: In this type of coherence if one planar face penetrates another, their line of intersection can be determined from two points of intersection.
  5. Area coherence: In this coherence two pixel areas are compared with one another
  6. Span coherence: Span coherence is a type of area coherence in which a span of adjacent pixels in a scan line is taken in to consideration.
  7. Scan line coherence: In this coherence two scan lines are compared with one another.
  8. Depth coherence: In this coherence two depths from a point are compared with one another.
  9. Frame coherence: In this coherence two frames are compared with one another.

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