Maths (Geometry): sin

       Name: sin                                                     [Show more]
       Type: Variable
   Category: Maths (Geometry)
    Summary: Table for sine values
    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * GetSineAndCosine uses sin


 This table contains sine values for a quarter of a circle, i.e. for the range
 0 to 90 degrees, or 0 to PI/2 radians. The table contains values for indexes
 0 to 127, which cover the quarter from 0 to PI/2 radians. Entry X in the table
 is therefore (X / 128) * (PI / 2) radians of the way round the quarter circle,
 so the table at index X contains the sine of this value.

 The value of sine across the quarter circle ranges from 0 to 1:

   sin(0) = 0

   sin(90) = sin(PI/2) = 1

 It might help to think of sin(X) as an integer ranging from 0 to 256 across
 the quarter circle, so entry X in this table contains sin(X) * 256, where X
 ranges from 0 to 128 over the course of a quarter circle.


.sin

 FOR I%, 0, 127

  N = INT(0.5 + 256 * SIN((I% / 128) * (PI / 2)))

  IF N >= 255
   EQUB 255
  ELSE
   EQUB N
  ENDIF

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