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.\" RCSid "$Id" |
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.\" RCSid "$Id$" |
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.TH RTRACE 1 10/17/97 RADIANCE |
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.SH NAME |
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rtrace - trace rays in RADIANCE scene |
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If the direction vector is (0,0,0), a bogus record |
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is printed and the output is flushed if the |
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.I -x |
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value is unset or zero. |
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value is one or zero. |
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(See the notes on this option below.)\0 |
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This may be useful for programs that run |
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.I rtrace |
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ascii, 'f' for single-precision floating point, |
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and 'd' for double-precision floating point. |
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In addition to these three choices, the character 'c' may be used |
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to denote 4-byte floating point (Radiance) color format |
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for the output of values only |
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.I (\-ov |
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option, below). |
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to denote 4-byte RGBE (Radiance) color format |
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for the output of individual color values only, and the |
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.I \-x |
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and |
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.I \-y |
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options should also be specified to create a valid output picture. |
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If the output character is missing, the input format is used. |
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.IP |
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Note that there is no space between this option and its argument. |
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.IP |
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v value (radiance) |
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.IP |
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V contribution (radiance) |
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+ |
.IP |
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w weight |
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.IP |
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W color coefficient |
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+ |
.IP |
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l effective length of ray |
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.IP |
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L first intersection distance |
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.IP |
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m modifier name |
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.IP |
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M material name |
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+ |
.IP |
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+ |
r mirrored value contribution |
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+ |
.IP |
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+ |
x unmirrored value contribution |
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+ |
.IP |
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+ |
R mirrored ray length |
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+ |
.IP |
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X unmirrored ray length |
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+ |
.IP |
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+ |
~ tilde (end of trace marker) |
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+ |
.IP |
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If the letter 't' appears in |
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.I spec, |
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then the fields following will be printed for every ray traced, |
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not just the final result. |
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If the capital letter 'T' is given instead of 't', then all rays will |
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be reported, including shadow testing rays to light sources. |
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Spawned rays are indented one tab for each level. |
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The tilde marker ('~') is a handy way of differentiating the final ray |
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value from daughter values in a traced ray tree, and usually appears |
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right before the 't' or 'T' output flags. |
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E.g., |
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.I \-ov~TmW |
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will emit a tilde followed by a tab at the end of each trace, |
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which can be easily distinguished even in binary output. |
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.IP |
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Note that there is no space between this option and its argument. |
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.TP |
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.BI -te \ mat |
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.BI -te \ mod |
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Append |
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< |
.I mat |
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> |
.I mod |
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to the trace exclude list, |
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so that it will not be reported by the trace option |
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.I (\-o*t*). |
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Any ray striking an object having |
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.I mat |
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> |
.I mod |
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as its modifier will not be reported to the standard output with |
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the rest of the rays being traced. |
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This option has no effect unless the 't' option has been given as |
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part of the output specifier. |
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Any number of excluded materials may be given, but each |
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This option has no effect unless either the 't' or 'T' |
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option has been given as part of the output specifier. |
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Any number of excluded modifiers may be given, but each |
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must appear in a separate option. |
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.TP |
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.BI -ti \ mat |
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.BI -ti \ mod |
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Add |
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< |
.I mat |
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> |
.I mod |
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to the trace include list, |
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so that it will be considered during the indirect calculation. |
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so that it will be reported by the trace option. |
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The program can use either an include list or an exclude |
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list, but not both. |
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.TP |
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.BI -tE \ file |
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Same as |
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.I \-te, |
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except read materials to be excluded from |
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except read modifiers to be excluded from |
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.I file. |
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The RAYPATH environment variable determines which directories are |
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searched for this file. |
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The material names are separated by white space in the file. |
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The modifier names are separated by white space in the file. |
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.TP |
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.BI -tI \ file |
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Same as |
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.I \-ti, |
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except read materials to be included from |
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except read modifiers to be included from |
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.I file. |
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.TP |
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.BR \-i |
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.I \-dv |
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option (below) may be used to override this. |
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This option is especially useful in |
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conjunction with ximage(1) for computing illuminance at scene points. |
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conjunction with ximage(1) for computing irradiance at scene points. |
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.TP |
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.BR \-u |
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Boolean switch to control uncorrelated random sampling. |
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When "off", a low-discrepancy sequence is used, which reduces |
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variance but can result in a brushed appearance in specular highlights. |
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When "on", pure Monte Carlo sampling is used in all calculations. |
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.TP |
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.BR \-I |
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Boolean switch to compute irradiance rather than radiance, |
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with the input origin and direction interpreted instead |
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.I res. |
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The output will be flushed after every |
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.I res |
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input rays. |
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input rays if |
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> |
.I \-y |
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is set to zero. |
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> |
A value of one means that every ray will be flushed, whatever |
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> |
the setting of |
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> |
.I \-y. |
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A value of zero means that no output flushing will take place. |
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.TP |
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.BI -y \ res |
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.I \-f |
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option, above.) |
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.TP |
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+ |
.BI -n \ nproc |
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Execute in parallel on |
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.I nproc |
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local processes. |
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This option is incompatible with the |
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.I \-P |
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and |
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+ |
.I \-PP, |
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options. |
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Multiple processes also do not work properly with ray tree output |
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using any of the |
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.I \-o*t* |
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options. |
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There is no benefit from specifying more processes than there are |
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cores available on the system or the |
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.I \-x |
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setting, which forces a wait at each flush. |
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+ |
.TP |
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|
.BI -dj \ frac |
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|
Set the direct jittering to |
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|
.I frac. |
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|
specification will be calculated. |
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|
.TP |
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|
.BI -dr \ N |
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< |
Set the number of relays for secondary sources to |
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> |
Set the number of relays for virtual sources to |
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|
.I N. |
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< |
A value of 0 means that secondary sources will be ignored. |
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> |
A value of 0 means that virtual sources will be ignored. |
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|
A value of 1 means that sources will be made into first generation |
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< |
secondary sources; a value of 2 means that first generation |
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< |
secondary sources will also be made into second generation secondary |
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> |
virtual sources; a value of 2 means that first generation |
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> |
virtual sources will also be made into second generation virtual |
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sources, and so on. |
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|
.TP |
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|
.BI -dp \ D |
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< |
Set the secondary source presampling density to D. |
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> |
Set the virtual source presampling density to D. |
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|
This is the number of samples per steradian |
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that will be used to determine ahead of time whether or not |
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it is worth following shadow rays through all the reflections and/or |
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transmissions associated with a secondary source path. |
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A value of 0 means that the full secondary source path will always |
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> |
transmissions associated with a virtual source path. |
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> |
A value of 0 means that the full virtual source path will always |
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be tested for shadows if it is tested at all. |
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|
.TP |
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.BR \-dv |
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|
.I \-i |
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|
option. |
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|
.TP |
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< |
.BI -sj \ frac |
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< |
Set the specular sampling jitter to |
| 350 |
< |
.I frac. |
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< |
This is the degree to which the highlights are sampled |
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< |
for rough specular materials. |
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< |
A value of one means that all highlights will be fully sampled |
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< |
using distributed ray tracing. |
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> |
.BI -ss \ samp |
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> |
Set the specular sampling to |
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> |
.I samp. |
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> |
For values less than 1, this is the degree to which the highlights |
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are sampled for rough specular materials. |
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> |
A value greater than one causes multiple ray samples to be sent |
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to reduce noise at a commmesurate cost. |
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A value of zero means that no jittering will take place, and all |
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reflections will appear sharp even when they should be diffuse. |
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.TP |
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.TP |
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.BR -bv |
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Boolean switch for back face visibility. |
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With this switch off, back faces of opaque objects will be invisible |
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< |
to all rays. |
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> |
With this switch off, back faces of all objects will be invisible |
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> |
to view rays. |
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This is dangerous unless the model was constructed such that |
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all surface normals on opaque objects face outward. |
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> |
all surface normals face outward. |
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Although turning off back face visibility does not save much |
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computation time under most circumstances, it may be useful as a |
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tool for scene debugging, or for seeing through one-sided walls from |
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the outside. |
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This option has no effect on transparent or translucent materials. |
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|
.TP |
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|
.BI -av " red grn blu" |
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|
Set the ambient value to a radiance of |
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|
.BI -ab \ N |
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|
Set the number of ambient bounces to |
| 413 |
|
.I N. |
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< |
This is the maximum number of diffuse bounces |
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< |
computed by the indirect calculation. |
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< |
A value of zero implies no indirect calculation. |
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> |
This is the maximum number of diffuse bounces computed by the indirect |
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calculation. A value of zero implies no indirect calculation. |
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> |
.IP |
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> |
This value defaults to 1 in photon mapping mode (see |
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> |
.I -ap |
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> |
below), implying that global photon irradiance is always computed via |
| 420 |
> |
.I one |
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> |
ambient bounce; this behaviour applies to any positive number of ambient |
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> |
bounces, regardless of the actual value specified. A negative value enables |
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a preview mode that directly visualises the irradiance from the global |
| 424 |
> |
photon map without any ambient bounces. |
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|
.TP |
| 426 |
|
.BI -ar \ res |
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|
Set the ambient resolution to |
| 444 |
|
Set the ambient accuracy to |
| 445 |
|
.I acc. |
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|
This value will approximately equal the error |
| 447 |
< |
from indirect illuminance interpolation. |
| 447 |
> |
from indirect irradiance interpolation. |
| 448 |
|
A value of zero implies no interpolation. |
| 449 |
|
.TP |
| 450 |
|
.BI -ad \ N |
| 451 |
|
Set the number of ambient divisions to |
| 452 |
|
.I N. |
| 453 |
|
The error in the Monte Carlo calculation of indirect |
| 454 |
< |
illuminance will be inversely proportional to the square |
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> |
irradiance will be inversely proportional to the square |
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|
root of this number. |
| 456 |
|
A value of zero implies no indirect calculation. |
| 457 |
|
.TP |
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|
.BI -af \ fname |
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|
Set the ambient file to |
| 466 |
|
.I fname. |
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< |
This is where indirect illuminance will be stored and retrieved. |
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< |
Normally, indirect illuminance values are kept in memory and |
| 467 |
> |
This is where indirect irradiance will be stored and retrieved. |
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> |
Normally, indirect irradiance values are kept in memory and |
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|
lost when the program finishes or dies. |
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< |
By using a file, different invocations can share illuminance |
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> |
By using a file, different invocations can share irradiance |
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|
values, saving time in the computation. |
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|
The ambient file is in a machine-independent binary format |
| 473 |
|
which can be examined with |
| 490 |
|
.I Getinfo(1) |
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|
may be used to print out this information. |
| 492 |
|
.TP |
| 493 |
< |
.BI -ae \ mat |
| 493 |
> |
.BI -ae \ mod |
| 494 |
|
Append |
| 495 |
< |
.I mat |
| 495 |
> |
.I mod |
| 496 |
|
to the ambient exclude list, |
| 497 |
|
so that it will not be considered during the indirect calculation. |
| 498 |
|
This is a hack for speeding the indirect computation by |
| 499 |
|
ignoring certain objects. |
| 500 |
|
Any object having |
| 501 |
< |
.I mat |
| 501 |
> |
.I mod |
| 502 |
|
as its modifier will get the default ambient |
| 503 |
|
level rather than a calculated value. |
| 504 |
< |
Any number of excluded materials may be given, but each |
| 504 |
> |
Any number of excluded modifiers may be given, but each |
| 505 |
|
must appear in a separate option. |
| 506 |
|
.TP |
| 507 |
< |
.BI -ai \ mat |
| 507 |
> |
.BI -ai \ mod |
| 508 |
|
Add |
| 509 |
< |
.I mat |
| 509 |
> |
.I mod |
| 510 |
|
to the ambient include list, |
| 511 |
|
so that it will be considered during the indirect calculation. |
| 512 |
|
The program can use either an include list or an exclude |
| 515 |
|
.BI -aE \ file |
| 516 |
|
Same as |
| 517 |
|
.I \-ae, |
| 518 |
< |
except read materials to be excluded from |
| 518 |
> |
except read modifiers to be excluded from |
| 519 |
|
.I file. |
| 520 |
|
The RAYPATH environment variable determines which directories are |
| 521 |
|
searched for this file. |
| 522 |
< |
The material names are separated by white space in the file. |
| 522 |
> |
The modifier names are separated by white space in the file. |
| 523 |
|
.TP |
| 524 |
|
.BI -aI \ file |
| 525 |
|
Same as |
| 526 |
|
.I \-ai, |
| 527 |
< |
except read materials to be included from |
| 527 |
> |
except read modifiers to be included from |
| 528 |
|
.I file. |
| 529 |
|
.TP |
| 530 |
+ |
.BI -ap " file [bwidth1 [bwidth2]]" |
| 531 |
+ |
Enable photon mapping mode. Loads a photon map generated with |
| 532 |
+ |
.I mkpmap(1) |
| 533 |
+ |
from |
| 534 |
+ |
.I file, |
| 535 |
+ |
and evaluates the indirect irradiance depending on the photon type |
| 536 |
+ |
(automagically detected) using density estimates with a bandwidth of |
| 537 |
+ |
.I bwidth1 |
| 538 |
+ |
photons, or the default bandwidth if none is specified (a warning will be |
| 539 |
+ |
issued in this case). |
| 540 |
+ |
.IP |
| 541 |
+ |
Global photon irradiance is evaluated as part of the ambient calculation (see |
| 542 |
+ |
.I \-ab |
| 543 |
+ |
above), caustic photon irradiance is evaluated at primary rays, and |
| 544 |
+ |
indirect inscattering in |
| 545 |
+ |
.I mist |
| 546 |
+ |
is accounted for by volume photons. Contribution photons are treated as |
| 547 |
+ |
global photons by |
| 548 |
+ |
.I rtrace. |
| 549 |
+ |
.IP |
| 550 |
+ |
Additionally specifying |
| 551 |
+ |
.I bwidth2 |
| 552 |
+ |
enables bias compensation for the density estimates with a |
| 553 |
+ |
minimum and maximum bandwidth of |
| 554 |
+ |
.I bwidth1 |
| 555 |
+ |
and |
| 556 |
+ |
.I bwidth2, |
| 557 |
+ |
respectively. |
| 558 |
+ |
.IP |
| 559 |
+ |
Global photon irradiance may be optionally precomputed by |
| 560 |
+ |
.I mkpmap(1), |
| 561 |
+ |
in which case the bandwidth, if specified, is ignored, as the nearest photon |
| 562 |
+ |
is invariably looked up. |
| 563 |
+ |
.IP |
| 564 |
+ |
Using direct photons replaces the direct calculation with density estimates |
| 565 |
+ |
for debugging and validation of photon emission. |
| 566 |
+ |
.TP |
| 567 |
+ |
.BI -am " frac" |
| 568 |
+ |
Maximum search radius for photon map lookups. Without this option, an |
| 569 |
+ |
initial maximum search radius is estimated for each photon map from the |
| 570 |
+ |
average photon distance to the distribution's centre of gravity. It is then |
| 571 |
+ |
adapted to the photon density in subsequent lookups. This option imposes a |
| 572 |
+ |
global fixed maximum search radius for |
| 573 |
+ |
.I all |
| 574 |
+ |
photon maps, thus defeating the automatic adaptation. It is useful when |
| 575 |
+ |
multiple warnings about short photon lookups are issued. Note that this |
| 576 |
+ |
option does not conflict with the bandwidth specified with the |
| 577 |
+ |
.I \-ap |
| 578 |
+ |
option; the number of photons found will not exceed the latter, but may be |
| 579 |
+ |
lower if the maximum search radius contains fewer photons, thus resulting in |
| 580 |
+ |
short lookups. Setting this radius too large, on the other hand, may |
| 581 |
+ |
degrade performance. |
| 582 |
+ |
.TP |
| 583 |
+ |
.BI -ac " pagesize" |
| 584 |
+ |
Set the photon cache page size when using out-of-core photon mapping. The |
| 585 |
+ |
photon cache reduces disk I/O incurred by on-demand loading (paging) of |
| 586 |
+ |
photons, and thus increases performance. This |
| 587 |
+ |
is expressed as a (float) multiple of the density estimate bandwidth |
| 588 |
+ |
specified with |
| 589 |
+ |
.I \-ap |
| 590 |
+ |
under the assumption that photon lookups are local to a cache page. Cache |
| 591 |
+ |
performance is sensitive to this parameter: larger pagesizes will reduce the |
| 592 |
+ |
paging frequency at the expense of higher latency when paging does occur. |
| 593 |
+ |
Sensible values are in the range 4 (default) to 16. |
| 594 |
+ |
.TP |
| 595 |
+ |
.BI -aC " cachesize" |
| 596 |
+ |
Set the total number of photons cached when using out-of-core photon |
| 597 |
+ |
mapping, taking into account the pagesize specified by |
| 598 |
+ |
.I \-ac. |
| 599 |
+ |
Note that this is approximate as the number of cache pages is rounded to |
| 600 |
+ |
the nearest prime. This allows adapting the cache to the available physical |
| 601 |
+ |
memory. In conjunction with the |
| 602 |
+ |
.I \-n |
| 603 |
+ |
option, this is the cache size |
| 604 |
+ |
.I per parallel process. |
| 605 |
+ |
Cache performance is less sensitive to this parameter, |
| 606 |
+ |
and reasonable performance can obtained with as few as 10k photons. The |
| 607 |
+ |
default is 1M. This option recognises multiplier suffixes (k = 1e3, M = |
| 608 |
+ |
1e6), both in upper and lower case. |
| 609 |
+ |
.TP |
| 610 |
|
.BI -me " rext gext bext" |
| 611 |
|
Set the global medium extinction coefficient to the indicated color, |
| 612 |
|
in units of 1/distance (distance in world coordinates). |
| 645 |
|
.TP |
| 646 |
|
.BI -lr \ N |
| 647 |
|
Limit reflections to a maximum of |
| 648 |
< |
.I N. |
| 648 |
> |
.I N, |
| 649 |
> |
if N is a positive integer. |
| 650 |
> |
If |
| 651 |
> |
.I N |
| 652 |
> |
is zero or negative, then Russian roulette is used for ray |
| 653 |
> |
termination, and the |
| 654 |
> |
.I -lw |
| 655 |
> |
setting (below) must be positive. |
| 656 |
> |
If N is a negative integer, then this limits the maximum |
| 657 |
> |
number of reflections even with Russian roulette. |
| 658 |
> |
In scenes with dielectrics and total internal reflection, |
| 659 |
> |
a setting of 0 (no limit) may cause a stack overflow. |
| 660 |
|
.TP |
| 661 |
|
.BI -lw \ frac |
| 662 |
|
Limit the weight of each ray to a minimum of |
| 663 |
|
.I frac. |
| 664 |
< |
During ray-tracing, a record is kept of the final contribution |
| 665 |
< |
a ray would have to the image. |
| 666 |
< |
If it is less then the specified minimum, the ray is not traced. |
| 664 |
> |
During ray-tracing, a record is kept of the estimated contribution |
| 665 |
> |
(weight) a ray would have in the image. |
| 666 |
> |
If this weight is less than the specified minimum and the |
| 667 |
> |
.I -lr |
| 668 |
> |
setting (above) is positive, the ray is not traced. |
| 669 |
> |
Otherwise, Russian roulette is used to |
| 670 |
> |
continue rays with a probability equal to the ray weight |
| 671 |
> |
divided by the given |
| 672 |
> |
.I frac. |
| 673 |
|
.TP |
| 674 |
|
.BR -ld |
| 675 |
|
Boolean switch to limit ray distance. |
| 730 |
|
on most multiprocessing platforms, since the |
| 731 |
|
.I fork(2) |
| 732 |
|
system call will share memory on a copy-on-write basis. |
| 733 |
+ |
.SH NOTES |
| 734 |
+ |
Photons are generally surface bound (an exception are volume photons), thus |
| 735 |
+ |
the ambient irradiance in photon mapping mode will be biased at positions |
| 736 |
+ |
which do not lie on a surface. |
| 737 |
|
.SH EXAMPLES |
| 738 |
|
To compute radiance values for the rays listed in samples.inp: |
| 739 |
|
.IP "" .2i |
| 740 |
< |
rtrace -ov scene.oct < samples.inp > radiance.out |
| 740 |
> |
rtrace \-ov scene.oct < samples.inp > radiance.out |
| 741 |
|
.PP |
| 742 |
< |
To compute illuminance values at locations selected with the 't' |
| 742 |
> |
To compute irradiance values at locations selected with the 't' |
| 743 |
|
command of |
| 744 |
|
.I ximage(1): |
| 745 |
|
.IP "" .2i |
| 746 |
< |
ximage scene.pic | rtrace -h -x 1 -i scene.oct | rcalc -e '$1=47.4*$1+120*$2+11.6*$3' |
| 746 |
> |
ximage scene.hdr | rtrace \-h \-x 1 \-i scene.oct | rcalc \-e '$1=47.4*$1+120*$2+11.6*$3' |
| 747 |
|
.PP |
| 748 |
|
To record the object identifier corresponding to each pixel in an image: |
| 749 |
|
.IP "" .2i |
| 750 |
< |
vwrays -fd scene.pic | rtrace -fda `vwrays -d scene.pic` -os scene.oct |
| 750 |
> |
vwrays \-fd scene.hdr | rtrace \-fda `vwrays \-d scene.hdr` \-os scene.oct |
| 751 |
|
.PP |
| 752 |
|
To compute an image with an unusual view mapping: |
| 753 |
|
.IP "" .2i |
| 754 |
< |
cnt 640 480 | rcalc -e 'xr:640;yr:480' -f unusual_view.cal | rtrace |
| 755 |
< |
-x 640 -y 480 -fac scene.oct > unusual.pic |
| 754 |
> |
cnt 480 640 | rcalc \-e 'xr:640;yr:480' \-f unusual_view.cal | rtrace |
| 755 |
> |
\-x 640 \-y 480 \-fac scene.oct > unusual.hdr |
| 756 |
> |
.PP |
| 757 |
> |
To compute ambient irradiance in photon mapping mode from a global photon |
| 758 |
> |
map global.pm via one ambient bounce, and from a caustic photon map |
| 759 |
> |
caustic.pm at sensor positions in samples.inp: |
| 760 |
> |
.IP "" .2i |
| 761 |
> |
rtrace -h -ov -ab 1 -ap global.pm 50 -ap caustic.pm 50 scene.oct < |
| 762 |
> |
samples.inp > illum.out |
| 763 |
|
.SH ENVIRONMENT |
| 764 |
|
RAYPATH the directories to check for auxiliary files. |
| 765 |
|
.SH FILES |
| 766 |
< |
/usr/tmp/rtXXXXXX common header information for picture sequence |
| 766 |
> |
/tmp/rtXXXXXX common header information for picture sequence |
| 767 |
|
.SH DIAGNOSTICS |
| 768 |
|
If the program terminates from an input related error, the exit status |
| 769 |
|
will be 1. |
| 777 |
|
.SH AUTHOR |
| 778 |
|
Greg Ward |
| 779 |
|
.SH "SEE ALSO" |
| 780 |
< |
getinfo(1), lookamb(1), oconv(1), pfilt(1), pinterp(1), |
| 781 |
< |
pvalue(1), rpict(1), rview(1), vwrays(1), ximage(1) |
| 780 |
> |
getinfo(1), lookamb(1), mkpmap(1), oconv(1), pfilt(1), pinterp(1), |
| 781 |
> |
pvalue(1), rcontrib(1), rsplit(1), |
| 782 |
> |
rpict(1), rtpict(1), rvu(1), vwrays(1), ximage(1) |
