Command: prism

Syntax

{<entity> = } prism <point> {
    <pcommand>
    ...
}

Description

Create a prism graphic entity.

Parameters

• <entity>
  An entity or gstructure identifier. The prism entity will be given this name.

• <point>
  An extrusion point phrase to be applied to all vertices defined in <pcommand> thereby forming the prism.

• <pcommand>
  A command line containing either:

a language command to be executed normally, which may or may not generate polygon vertices, or

a series of point expressions separated by commas defining polygon vertices.

Switches

• -alph=<num>
  An alpha transparency factor between 0 and 1. A value 1 implies fully opaque, 0 means fully transparent (therefore invisible). The default is 1.

• -br=<num>
  A brightness factor between -1 and +1. A value 0 means normal, -1 means very dark (black), +1 means very bright (white). The default is 1.

• -col=<color>
  The color of the prism. If included, this will override any color defined in the linestyle (-ls) or fillstyle (-fil). If omitted, the value no_change is used.

• -draw
  Display the entity graphics during creation. The default behavior is to suppress display until completion of the command, unless the command was typed from the keyboard.

• -ff
  Fix the fill color so that it is unaffected by subsequent modifications to the entity color.

• -fil=<fillstyle>
  The fill characteristics of the prism facets. If omitted, the facets are not filled. Note: <fillstyle> can be a fillstyle, color, tile, hatchstyle or graduation.

• -fr=<num>
  Define a fragment number for the entity. If omitted, the default fragment def_fragment is used.

• -g=<groups>
  The graphic groups of which the entity is to be a member.

• -ls=<num>
  The linestyle of the prism edges. This can be a linestyle or a color. If omitted, the current modeling color (def_color) is used.

• -ra=<num>
  Define a rank for the entity. If omitted, the default rank def_rank is used.

• -th=<num>
  The thickness of the edges. If included, this will override any thickness defined in the linestyle (-ls) or hatchstyle (-fil), if applicable.

Notes

This command always creates a graphic entity unless the prism has a null height. Duplicate consecutive vertices are ignored.

The symbology of polygon edges may be changed by using relevant assignments within the command block, e.g. def_color = red.

During edge definition, a point phrase beginning with a @ will indicate an invisible edge. A phrase beginning with $ will indicate a linestyled edge, using linestyle def_ls. If neither prefix is present, the linestyle given by the -ls switch is used.

Examples

Create an unnamed 6-faceted prism.

prism u:250 { gc, e:500, n:500, w:250, r }

Create an unnamed prism entity (the edges are defined interactively).

plan
prism u:700, -ls=red, -fil=green {
    pseries; # Command
    r; # Point phrase 'return to start'
}

Create a named prism entity in a command block (via a regular polygon of 64 edges).

angle_mode='radians'
numeric nedges = 64, radius = 1000
numeric ang = 0, delta = 1.5*pi/nedges
entity tent = prism (500,500,1500), -fil=blue {
    for i=1,nedges {
        (radius*sin(ang),radius*cos(ang),0)
        ang += delta
    }
}

See Also