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#### Vector Identifiers

Vector identifiers may be declared to make scene files more readable and to parameterize scenes so that changing a single declaration changes many values. An identifier is declared as follows.

VECTOR_DECLARATION:
`
  #declare
`IDENTIFIER `=` EXPRESSION`;` | `
  #local
`IDENTIFIER `=` EXPRESSION`;`

Where IDENTIFIER is the name of the identifier up to 40 characters long and EXPRESSION is any valid expression which evaluates to a vector value. Note that there should be a semi-colon after the expression in a vector declaration. This semi-colon is new with POV-Ray version 3.1. If omitted, it generates a warning and some macros may not work properly. See "#declare vs. #local" for information on identifier scope. Here are some examples....

     #declare Here = <1,2,3>;

     #declare There = <3,4,5>;

     #declare Jump = <Foo*2,Bar-1,Bob/3>;

     #declare Route = There-Here;

     #declare Jump = Jump+<1,2,3>;

Note that you invoke a vector identifier by using its name without any angle brackets. As the last example shows, you can re-declare a vector identifier and may use previously declared values in that re-declaration. There are several built-in identifiers which POV-Ray declares for you. See section "Built-in Vector Identifiers" for details.

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