Data Types

Various data types are defined by TSIPP. They are all built as Tcl lists, so standard list operations can be used to construct and access them. The tcl_precision variable is used when formatting all floating point numbers. The value of this variable is set to the Tcl defined maximum less one when TSIPP is initialized. In many cases, the precision can be reduce for a slight increase in performance without altering the generation of images. The following data structures are used by TSIPP:

• color - A list containing the red, green and blue values for the surface. Each being a number between 0.0 and 1.0.
• opacity - Describes the opacity of a surface. 0.0 means totally transparent, 1.0 means totally opaque. May be a list of red, green and blue opacity values or a single value to be used for all color channels.
• vertex - A vertex is defined by a Tcl list of 3 floating point numbers in the form: {x y z}.
• vertex/texture pair - A vertex and corresponding texture coordinates are defined by a Tcl list of two list, each having 3 floating point numbers in the form: {{x y z} {u v w}}.
• vector - A vector is defined by a Tcl list of 3 floating point numbers in the form: {x y z}.
• boolean - Boolean arguments may be specified as 0 or 1, true or false, t or f (upper or lower case). Only 0 or 1 are valid in Tcl expressions and commands that return booleans only return 0 or 1.
• angle - An angle may be expressed in degrees or radians. If the number is prefixed with an R, then it is taken as radians, if it is prefixed with D, then it is taken as degrees. (e.g. 1.2, R1.2, D10.5). If no prefix is specified, some commands assume degrees, some assume radians. See the documentation of the specific command.
• matrix - A 4x4 transformation matrix is represented as a list of 4 elements, each element being a row. Each of the row elements is a list of 4 floating point numbers, representing the columns. The values in column 4 must be 0, 0, 0, 1. For example:

          {{1.2  1.4  0.1  0}
           {2.1  2.3  1.6  0}
           {2.4  6.1  2.6  0}
           {2.9  1.1  3.6  1}}
  

Be careful, many commands take lists of the above data types, which are themselves lists.