pick_depth(3G)

NAME

pick_depth − define pick depth for pick_from_segment and hit_mode

SYNOPSIS

C Syntax:

void set_pick_depth(fildes,p_front,p_back)
int fildes;
float p_front,p_back;

void inq_pick_depth(fildes,p_front,p_back)
int fildes;
float *p_front,*p_back;

FORTRAN77 Syntax:

subroutine set_pick_depth(fildes,p_front,p_back)
integer*4 fildes
real p_front,p_back

subroutine inq_pick_depth(fildes,p_front,p_back)
integer*4 fildes
real p_front,p_back

Pascal Syntax:

procedure set_pick_depth(fildes:integer; p_front,p_back:real);

procedure inq_pick_depth(fildes:integer; var p_front,p_back:real);

DESCRIPTION

Input Parameters

fildes Integer file descriptor returned by gopen when an I/O path to a graphics device is opened.

p_front Specifies the front pick aperture plane in perspective coordinates; i.e., comparison with the pick aperture is performed after the primitives are transformed by the current transformation matrix. Perspective divide occurs after the front and back clip.

p_back Specifies the back pick aperture plane in perspective coordinates; i.e., comparison with the pick aperture performed after the primitives are transformed by the current transformation matrix. Perspective divide occurs after the front and back clip.

Discussion

Set_pick_depth sets a front and back z plane which together with pick_window defines the pick aperture. Inq_pick_depth returns the current set values for the pick depth.

The pick depth is used for hit testing when the Starbase hit mode is enabled (see hit_mode(3G)). Hit testing is also done by pick_from_segment(3G).

Some picking modes (see set_pick_mode(3G) in the Starbase Display List Programmers Manual) may cause pick_from_segment(3G) to alter the pick depth.

ERRORS

1 Graphics device is not initialized for this operation.

DEFAULTS

p_front: −10000.0

p_back: 10000.0

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