home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Crawly Crypt Collection 1
/
crawlyvol1.bin
/
tt
/
raysh402
/
guide.tex
/
node11_mn.html
< prev
next >
Wrap
Text File
|
1992-02-09
|
2KB
|
43 lines
<H1><A ID="SECTION00450000000000000000">
The Ray Tree</A>
</H1>
<P>
When ray tracing a scene, reflected or transmitted rays may strike
other reflective or transparent objects. Further reflected or
transmitted rays will be spawned, and so on. Taken together, such
a family of rays is termed the <#202#><EM>ray tree</EM><#202#>. Care must be taken
to control the depth of this tree: If it is allowed to grow too deeply,
one may spend a great deal of time computing rays that contribute little
to the final picture; if it is not allowed to grow far enough, this
premature tree pruning may be evident in the image.
<P>
<#203#><#1791#><EM>Rayshade</EM><#1791#><#203#> provides two complementary methods for controlling the depth
of the ray tree. One method sets an absolute maximum for the tree. The
other allows one to adaptively prune a tree as it grows so that ``unimportant''
rays are not spawned.
<P>
<DL>
<DT><STRONG><#4635#><#4635#></STRONG></DT>
<DD><#1194#><TT>maxdepth</TT><#1194#> <#1195#><EM>level</EM><#1195#>
<BR> Do not spawn rays deeper than those at the given <#207#><EM>level</EM><#207#>.
</DD>
</DL>Rays from the eye are of depth zero. The default value for
<#209#><EM>level</EM><#209#> is 15.
This depth may also be set from the command line through the <#210#><TT>-D</TT><#210#> option.
<P>
<DL>
<DT><STRONG><#4636#><#4636#></STRONG></DT>
<DD><#1198#><TT>cutoff</TT><#1198#> <#1199#><EM>threshold</EM><#1199#>
<BR> Do not spawn rays whose contribution to the final color of
the eye ray is less than <#214#><EM>threshold</EM><#214#> for each color channel.
Threshold may be given as a single floating-point value,
or as a red-green-blue triple.
</DD>
</DL>The default value is 0.002. This threshold may also be set from
the command line through the <#216#><TT>-T</TT><#216#> option.