In VRML display mode, there may be multiple levels in a slide. Levels are used to allow for incremental presentation of the content of slide.

Each element in a slide, may have an indication of start and end level. Some tags allow for a indicating automatic increments of the start level, which is usually indicated with level=auto.

creating slides

There are a number of contexts, and associated file types, in which slides may be created:

• .t -- the ultimately generic format, uses all filters
• .tm -- limited .t format with VRML support, uses ht-ml.flt + vr-ml.flt
• .pvl -- VRML slides support, uses vr-ml.flt -pvl
• .es -- for the use of slides in worlds

See example makefiles for actual usage

parameters for vr-ml.flt

• none -- plain generation of VRML
• -pvl -- generates pvl includes
• -x -- creates also links for hrefs (UDF)

The VRML protos supporting the slides format must be kept simple and basic. In some cases extra tags are needed to get the desired result (or an approximation of that).

extra tags

• <+n> -- create n additional horizontal space (float n)
• <-n> -- for negative spacing

• always use a <p> tag after ending a list or display.

Also, the filtering is done on an as best as possible basis. In some cases it will be very hard to get what you want. Actually, since it is a legaccy format, you're not even supposed to use it. So, why bother.

on the design of the tag structure

To accomodate the various modes of formatting and the various uses that can be made of the slide format, we make a number of assumptions:

• processing (in presentation mode) should be fast
• the tags must be intuitive, and easy to type (keyboard-wise)
• the tags must support a sufficiently rich rethoric repertoire

• id -- unique name (obligatory)
• caption -- slides caption (for use in latex)

---

• mode -- UDF (undocumented feature)
• style -- generic style attribute (UDF)

---

• transform attributes -- trans, scale, rotate
• (VRML) style tags -- bgcolor, textcolor

• transform attributes -- trans, scale, rotate
• (VRML) style tags -- bgcolor, textcolor

Both unnumbered and numbered list are allowed, as in HTML

• level -- with level=auto the bullets will appear in order
• additional attributes -- UDFs

To indicate items in a list use the <li> tag. When additional lines are need, use the line tag.

beware (may/must change (MC))

The text after a bullet or number must be on one line, additional lines need to be indicated with a tag.

the dl list tag

Should have

• level

Use the <dt> and <dd> tags to create the items for the list.

displays

To allow for unformatted text, such as program text the display tag is supported, which is like the <pre> tag in HTML.

• level -- with level=auto lines will appear in order
• size -- to give the size of the text used in the display

• color
• size
• style
• family

• <i>...</i> -- italic
• <b>...</b> -- bold
• <em>...</em> -- emphasize
• <tt>...</tt> -- typewriter
• <rm>...</rm> -- roman

• <red>...</red> -- red
• <blue>...</blue> -- blue
• <yellow>...</yellow> -- yellow
• <green>...</green> -- green
• <white>...</white> -- white
• <black>...</black> -- black
• <gold>...</gold> -- gold
• <silver>...</silver> -- silver

It might be worthwhile to incorporate VRML objects in a slide. These are only visible in VRML, naturally.

As an example:

  <object>
  Transform { translation 9 0 -4 children [
  <include file=sensor.wrl>
  ] }
  </object> 
  

Note that the VRML text is automatically hidden when using the object tag. The include tag is a feature of the .t format.

hiding VRML

The <vrml> and </vrml> tags are needed if you don't want your VRML code to be displayed in HTML.