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The extension provides special effects that can be used with any -pic <object> by defining |[|<shape>|]| modifiers. The modification is local to the <object> currently being built, so will have no effect if this object is never actually used.

The following table lists the modifiers that have so far been defined. They come in two types – either a single keyword, or a key-character with the following text treated as a single argument.

$\begin{defs} \vert[@]\vert & align with current direction\cr \vert[@\vert<dire... ...ale to double size \cr \vert[halfsize]\vert & scale to half size \cr \end{defs}$

These |[|<shape>|]| modifiers specify transformations of the <object> currently being built. If the object has a rectangle edge then the size of the rectangle is transformed to enclose the transformed object; with a circle edge the radius is altered appropriately.

2 The |[@*]| form repeats the set of transformations applied to the last object which has been transformed, possibly in an earlier diagram. The |[@=|<word>|]| form allows a set of transformations to be saved and used later, simply by specifying |[|<word>|]|.

Each successive transformation acts upon the result of all previous. One consequence of this is that the order of the shape modifiers can make a significant difference in appearance—in general, transformations do not commute. Even successive rotations can give different sized rectangles if taken in the reverse order.

Sometimes this change of size is not desirable. The following commands are provided to modify this behaviour.

$\begin{defs} \vert\NoResizing\vert & prevents size adjustment \cr \vert\UseResizing\vert & restores size adjustments \cr \end{defs}$

3 The || command is also useful to have at the beginning of a document being typeset using a driver that cannot support scaling effects, in particular when applied to whole diagrams. In any case an unscaled version will result, but now the spacing and positioning will be appropriate to the unscaled rather than the scaled size.