surf_illum_quality(3G)
NAME
surf_illum_quality, inq_surf_illum_quality − set/inquire the quality with which the illumination of surfaces will be computed for radiosity renderings
SYNOPSIS
C Syntax:
void surf_illum_quality(fildes,quality);
int fildes,quality;
void inq_surf_illum_quality(fildes,quality);
int fildes,*quality;
FORTRAN77 Syntax:
subroutine surf_illum_quality(fildes,quality)
integer*4 fildes,quality
subroutine inq_surf_illum_quality(fildes,quality)
integer*4 fildes,quality
Pascal Syntax:
procedure surf_illum_quality(fildes,quality:integer);
procedure inq_surf_illum_quality(fildes:integer;
var quality:integer);
DESCRIPTION
Input Parameters
fildes Integer file descriptor returned by gopen when an I/O path to a graphics device is opened.
Input/Output Parameters
quality Illumination quality parameter. Can vary from 0 to 4.
Discussion
surf_illum_quality controls, and inq_surf_illum_quality inquires the accuracy with which shading is computed at surface sample points during radiosity rendering. Increasing the accuracy of light level calculations generally improves the quality of shadows in the rendered image.
The value of the quality parameter determines the level of accuracy that will be used in calculating illumination at all subsequently encountered sample points. The default value of 0 specifies the least accurate calculations while values 1 through 4 provide increasing levels of accuracy. Note that the time cost of radiosity calculations increases as the accuracy level is increased.
surf_illum_quality may be called as often as necessary during the segment. The illumination quality for a given surface is determined by the most recent call to surf_illum_quality. Because a higher quality setting increases computation time, it is often desirable to set higher quality only for areas of the model with the most visual importance.
The effect of changing the quality parameter is most apparent in the quality the soft-edged shadows that are produced by area light sources. Obtaining realistic soft-edge shadows from a very large area light source may require a higher quality setting than for a smaller source. Likewise, accurately capturing the effect of light reflected from a very large polygon (for example, a single polygon modeling the entire floor of a room) may also require a high quality setting. It is important to remember that the illumination quality applies to the surface receiving the illumination or shadows.
NOTES
Both surf_illum_quality and surf_shading_resolution affect the quality of radiosity rendering. surf_shading_resolution determines the level of shadow detail that can be captured by determining the number of points across a surface at which illumination will be computed, while surf_illum_quality controls how accurately the shading is determined at each of these points. Experimenting with different settings for both these commands should yield the optimum settings for the types of images you typically produce.
surf_illum_quality only affects the computation of radiosity renderings. Ray traced renderings are not affected by this command, nor are any of the standard Starbase lighting models.
ERRORS
Invalid file descriptor.
quality less than 0.
DEFAULTS
quality = 0.
SEE ALSO
— July 12, 1991