DEPTH_CUE(3G)

NAME

depth_cue − enable/disable depth cueing of output primitives

SYNOPSIS

C Syntax:

void depth_cue(fildes,on,min);
int fildes, on;
float min;

FORTRAN77 Syntax:

subroutine depth_cue(fildes, on, min)
integer*4 fildes, on
real min

Pascal Syntax:

procedure depth_cue(fildes, on:integer; min:real);

DESCRIPTION

Input Parameters

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

on If TRUE (1), output primitives are depth cued.
If FALSE (0), output primitives are not depth cued.

min Minimum intensity for the most distant primitives (range 0.0 to 1.0)

Discussion

Depth cueing modulates the intensity of output primitives proportional to the distance away from the viewer. Primitives at the nearest (front) clipping plane appear at full intensity as set by line_color, fill_color, etc. Primitives at the most distant (rear) clipping plane are dimmer by the factor min, with a linear interpolation of values in between.

Depth cueing can also be performed according to a more advanced model by calling depth_cue_color and depth_cue_range. Calling these routines allows specification of the background color to depth cue towards, and the front and back planes. If either of these routines is called, the min parameter for depth_cue is ignored. However, the on parameter for depth_cue is still used to enable or disable depth cueing.

CMAP_MONOTONIC or CMAP_FULL mode must be set with the shade_mode procedure before depth cueing is turned on.

Recommendation

Enable front and back clipping (use depth_indicator) when depth cueing is enabled.

DEFAULTS

on = FALSE (0):output primitives drawn without depth cueing.

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