Formats of markers

Visible markers can be set to arbitrary 3D positions. They correspond to classes inherited from G4VMarker in GEANT4. The ending string ``2D'' or ``2DS'' of each marker name, e.g. /MarkSquare2D and /MarkSquare2DS, means that every marker always shows its front face towards the view point, and so, for example, a marker /MarkSquare2D always looks as right square. The marked 3D positions are expressed with the current body coordinates. Colors are decided by the current color attribute. As for marker size, there are some points to be well understood in use:

1.

A unit of marker size is either the real 3D-world unit or the 2D unit on screen:

(a)

Size of a marker whose name ends with character `S', e.g.
/MarkCircle2DS, is described with the 2D unit on screen.

(b)

Size of a marker whose name does not end with character `S', e.g. /MarkCircle2D is described with the 3D unit.

2.

The 2D unit is recognized as ``pixel'' on computer displays and ``pt'' (1[pt]= (25.4/72)mm) on printed out papers.

3.

For /MarkText2D and /MarkText2DS, their marker sizes mean font sizes.

Note that in GEANT4 sizes of markers are given as diameters, while in g4.prim-format data they are given as radii.

An important feature of markers is that they are always drawn at the end of visualization, such that they can always become visible. In other words, hidden surface elimination is not applied to markers.