CLIP_DEPTH(3G)

NAME

clip_depth − define front and back clipping planes

SYNOPSIS

C Syntax:

void clip_depth(fildes,front,back);
int fildes;
float front,back;

FORTRAN77 Syntax:

subroutine clip_depth(fildes,front,back)
integer*4 fildes
real front,back

Pascal Syntax:

procedure clip_depth(fildes:integer;front,back:real);

DESCRIPTION

Input Parameters

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

front specifies the front clipping plane in perspective vdc coordinates; i.e., clipping is performed after the primitives are transformed by the current transformation matrix from modelling coordinates to vdc coordinates. Perspective divide occurs after the front and back clip.

back specifies the back clipping plane in perspective vdc coordinates; i.e., clipping is performed after the primitives are transformed by the current transformation matrix from modelling coordinates to vdc coordinates. Perspective divide is performed after the front and back clip.

Discussion

Clip_depth specifies the front and back clipping planes. Front must be less than back. Clip_depth does not enable/disable front or back clipping. Clipping to these planes is enabled or disabled using the front_on,back_on parameter of the depth_indicator procedure. This procedure also determines the range of transformed z values. This range is useful when implementing hidden surface removal procedures.

clip_depth values are also reset to the full z extent of the virtual device coordinates whenever vdc_extent is changed. This is a change present in all revisions after, and including the 5.18 release(on series 300) and is different from previous behavior!!!

DEFAULTS

front = 0.0, back = 1.0.

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