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 FALSE (0), output primitives are not depth cued.
If TRUE (1), output primitives are depth cued using the current model or the model selected by DC_MIN or DC_COLOR. The values FALSE and TRUE may be ORed with the following to select the depth cue model to be used. If neither of the following values are specified, or if both values are specified, the current depth cue model is not changed. DC_MIN output primitives are depth cued using the min parameter.
DC_COLOR output primitives are depth cued using the color and reference planes specified by depth_cue_color and depth_cue_range.

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. When using DC_MIN, 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 (DC_COLOR) 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. When the DC_COLOR model is used, the min parameter for depth_cue is ignored. However, the on parameter for depth_cue is used to enable or disable depth cueing and select the model.

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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