NAME

DoMinBoundingVolExt − Create an attribute object which specifies the minimum renderable bounding extent

SYNOPSIS

C:

DtObject DoMinBoundingVolExt(extension)
DtReal extension;

FORTRAN:

INTEGER∗4 DOMBVE(EXTENS)
REAL∗8 EXTENS

DESCRIPTION

DoMinBoundingVolExt creates an attribute object which specifies the minimum renderable bounding extent.  The parameter extension specifies a length in device coordinates (pixels).  A bounding volume (specified with DoBoundingVol <DOBV>) will be compared with this length to determine whether an alternate object (also specified with DoBoundingVol <DOBV> will be rendered instead of the remaining objects in the current group. 

The bounding volume object’s intersection with the display volume is computed when a bounding volume object is executed.  If the intersection is empty, that is if the bounding volume is not currently visible, then execution of the current group is aborted, and nothing else in the group will be drawn.  If the intersection is not empty, then a further test is made.  First, the smallest right rectangle that can enclose the projection of the bounding volume on the device is computed.  Then, if the length of the diagonal of that rectangle is less than the current minimum bounding extension, then execution of the current group will be aborted and the alternate object specified by DoBoundingVol <DOBV> will be executed in its place. 

See DoBoundingVol for more information on the process used to determine whether an object or its alternate representation should be rendered. 

DEFAULTS

The default value for DoMinBoundingVolExt is 2.0 pixels. 

SEE ALSO

DoBoundingVol(3D), DoBoundingVolSwitch(3D), DsCompBoundingVol(3D)

March 13, 1992