--- ray/doc/man/man1/rpict.1	2014/01/25 18:27:39	1.16
+++ ray/doc/man/man1/rpict.1	2022/10/19 21:25:20	1.28
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rpict.1,v 1.16 2014/01/25 18:27:39 greg Exp $"
+.\" RCSid "$Id: rpict.1,v 1.28 2022/10/19 21:25:20 greg Exp $"
 .TH RPICT 1 2/26/99 RADIANCE
 .SH NAME
 rpict - generate a RADIANCE picture
@@ -18,6 +18,8 @@ rpict - generate a RADIANCE picture
 ]
 .br
 .B "rpict [ options ] \-defaults"
+.br
+.B "rpict \-features [feat1 ..]"
 .SH DESCRIPTION
 .I Rpict
 generates a picture from the RADIANCE scene given in
@@ -41,6 +43,21 @@ In the second form shown above, the default values
 for the options (modified by those options present)
 are printed with a brief explanation.
 .PP
+In the third form, a list of supported features is sent
+to the standard output, one per line.
+If additional arguments follow, they are checked for presence in
+this list.
+If a feature includes subfeatures, these may be checked as well by
+specifying:
+.nf
+
+	rpict -features FeatName=subfeat1,subfeat2
+
+.fi
+If any named feature or subfeature is missing, an error is
+reported and the program returns an error status.
+If all of the named features are present, a zero status is returned.
+.PP
 Most options are followed by one or more arguments, which must be
 separated from the option and each other by white space.
 The exceptions to this rule are the 
@@ -211,10 +228,10 @@ Set the pixel sample jitter to
 Distributed ray-tracing performs anti-aliasing by randomly sampling
 over pixels.
 A value of one will randomly distribute samples over full
-pixels.
+pixels, and is not really recommended due to the tendency of
+samples to (nearly) coincide.
 A value of zero samples pixel centers only.
-A value between zero and one is usually best
-for low-resolution images.
+A value around 0.5-0.8 is typical.
 .TP
 .BI -pm \ frac
 Set the pixel motion blur to
@@ -310,21 +327,21 @@ change greater than the
 specification will be calculated.
 .TP
 .BI -dr \ N
-Set the number of relays for secondary sources to
+Set the number of relays for virtual sources to
 .I N.
-A value of 0 means that secondary sources will be ignored.
+A value of 0 means that virtual sources will be ignored.
 A value of 1 means that sources will be made into first generation
-secondary sources; a value of 2 means that first generation
-secondary sources will also be made into second generation secondary
+virtual sources; a value of 2 means that first generation
+virtual sources will also be made into second generation virtual
 sources, and so on.
 .TP
 .BI -dp \ D
-Set the secondary source presampling density to D.
+Set the virtual source presampling density to D.
 This is the number of samples per steradian 
 that will be used to determine ahead of time whether or not
 it is worth following shadow rays through all the reflections and/or
-transmissions associated with a secondary source path.
-A value of 0 means that the full secondary source path will always
+transmissions associated with a virtual source path.
+A value of 0 means that the full virtual source path will always
 be tested for shadows if it is tested at all.
 .TP
 .BR \-dv
@@ -405,9 +422,17 @@ indirect contributions, such as when both indoor and o
 .BI -ab \ N
 Set the number of ambient bounces to
 .I N.
-This is the maximum number of diffuse bounces 
-computed by the indirect calculation.
-A value of zero implies no indirect calculation.
+This is the maximum number of diffuse bounces computed by the indirect
+calculation. A value of zero implies no indirect calculation. 
+.IP
+This value defaults to 1 in photon mapping mode (see
+.I -ap
+below), implying that global photon irradiance is always computed via
+.I one
+ambient bounce; this behaviour applies to any positive number of ambient
+bounces, regardless of the actual value specified.  A negative value enables
+a preview mode that directly visualises the irradiance from the global
+photon map without any ambient bounces.
 .TP
 .BI -ar \ res
 Set the ambient resolution to
@@ -431,14 +456,14 @@ A value of zero is interpreted as unlimited resolution
 Set the ambient accuracy to
 .I acc.
 This value will approximately equal the error
-from indirect illuminance interpolation.
+from indirect irradiance interpolation.
 A value of zero implies no interpolation.
 .TP
 .BI -ad \ N
 Set the number of ambient divisions to
 .I N.
 The error in the Monte Carlo calculation of indirect
-illuminance will be inversely proportional to the square
+irradiance will be inversely proportional to the square
 root of this number.
 A value of zero implies no indirect calculation.
 .TP
@@ -451,13 +476,15 @@ show a significant change.
 .BI -af \ fname
 Set the ambient file to
 .I fname.
-This is where indirect illuminance will be stored and retrieved.
-Normally, indirect illuminance values are kept in memory and
+This is where indirect irradiance will be stored and retrieved.
+Normally, indirect irradiance values are kept in memory and
 lost when the program finishes or dies.
-By using a file, different invocations can share illuminance
+By using a file, different invocations can share irradiance
 values, saving time in the computation.
-Also, by creating an ambient file during a low resolution rendering,
-better results can be obtained in a second high resolution pass.
+Also, by creating an ambient file during a low-resolution rendering,
+better results can be obtained in a second high-resolution pass.
+(It is a good idea to keep all of the calculation parameters the same,
+changing only the dimensions of the output picture.)\0
 The ambient file is in a machine-independent binary format
 which may be examined with
 .I lookamb(1).
@@ -516,6 +543,82 @@ Same as
 except read modifiers to be included from
 .I file.
 .TP
+.BI -ap " file [bwidth1 [bwidth2]]"
+Enable photon mapping mode. Loads a photon map generated with
+.I mkpmap(1)
+from
+.I file,
+and evaluates the indirect irradiance depending on the photon type 
+(automagically detected) using density estimates with a bandwidth of
+.I bwidth1
+photons, or the default bandwidth if none is specified (a warning will be
+issued in this case).
+.IP
+Global photon irradiance is evaluated as part of the ambient calculation (see
+.I \-ab
+above), caustic photon irradiance is evaluated at primary rays, and 
+indirect inscattering in 
+.I mist
+is accounted for by volume photons. Contribution photons are treated as
+global photons by
+.I rpict.
+.IP
+Additionally specifying 
+.I bwidth2
+enables bias compensation for the density estimates with a
+minimum and maximum bandwidth of
+.I bwidth1
+and
+.I bwidth2,
+respectively.
+.IP
+Global photon irradiance may be optionally precomputed by
+.I mkpmap(1),
+in which case the bandwidth, if specified, is ignored, as the nearest photon
+is invariably looked up.
+.IP
+Using direct photons replaces the direct calculation with density estimates
+for debugging and validation of photon emission.
+.TP
+.BI -am " frac"
+Maximum search radius for photon map lookups.  Without this option, an
+initial maximum search radius is estimated for each photon map from the
+average photon distance to the distribution's centre of gravity.  It is then
+adapted to the photon density in subsequent lookups.  This option imposes a
+global fixed maximum search radius for
+.I all
+photon maps, thus defeating the automatic adaptation.  It is useful when
+multiple warnings about short photon lookups are issued.  Note that this
+option does not conflict with the bandwidth specified with the
+.I \-ap
+option; the number of photons found will not exceed the latter, but may be
+lower if the maximum search radius contains fewer photons, thus resulting in
+short lookups.  Setting this radius too large, on the other hand, may
+degrade performance.
+.TP
+.BI -ac " pagesize"
+Set the photon cache page size when using out-of-core photon mapping. The
+photon cache reduces disk I/O incurred by on-demand loading (paging) of
+photons, and thus increases performance. This
+is expressed as a (float) multiple of the density estimate bandwidth
+specified with
+.I \-ap
+under the assumption that photon lookups are local to a cache page. Cache
+performance is sensitive to this parameter: larger pagesizes will reduce the
+paging frequency at the expense of higher latency when paging does occur.
+Sensible values are in the range 4 (default) to 16.
+.TP
+.BI -aC " cachesize"
+Set the total number of photons cached when using out-of-core photon
+mapping, taking into account the pagesize specified by
+.I \-ac. 
+Note that this is approximate as the number of cache pages is rounded to
+the nearest prime. This allows adapting the cache to the available physical
+memory. Cache performance is less sensitive to this parameter, and reasonable 
+performance can obtained with as few as 10k photons. The default is 1M. This 
+option recognises multiplier suffixes (k = 1e3, M = 1e6), both in upper and 
+lower case.
+.TP
 .BI -me " rext gext bext"
 Set the global medium extinction coefficient to the indicated color,
 in units of 1/distance (distance in world coordinates).
@@ -565,7 +668,7 @@ option (above) may be used to override this.
 .BR \-u
 Boolean switch to control uncorrelated random sampling.
 When "off", a low-discrepancy sequence is used, which reduces
-variance but can result in a brushed appearance in specular highlights.
+variance but can result in a dithered appearance in specular highlights.
 When "on", pure Monte Carlo sampling is used in all calculations.
 .TP
 .BI -lr \ N
@@ -578,8 +681,8 @@ is zero, then Russian roulette is used for ray
 termination, and the
 .I -lw
 setting (below) must be positive.
-If N is a negative integer, then this sets the upper limit
-of reflections past which Russian roulette will be used.
+If N is a negative integer, then this limits the maximum
+number of reflections even with Russian roulette.
 In scenes with dielectrics and total internal reflection,
 a setting of 0 (no limit) may cause a stack overflow.
 .TP
@@ -799,6 +902,13 @@ this option turns them off.
 rpict \-vp 10 5 3 \-vd 1 \-.5 0 scene.oct > scene.hdr
 .PP
 rpict \-S 1 \-o frame%02d.hdr scene.oct < keyframes.vf
+.PP
+To render ambient irradiance in photon mapping mode from a global photon 
+map global.pm via one ambient bounce, and from a caustic photon map 
+caustic.pm:
+.IP "" .2i
+rpict -ab 1 -ap global.pm 50 -ap caustic.pm 50 -vf scene.vf scene.oct > 
+scene.hdr
 .SH ENVIRONMENT
 RAYPATH		the directories to check for auxiliary files.
 .SH FILES
@@ -818,5 +928,5 @@ option.
 .SH AUTHOR
 Greg Ward
 .SH "SEE ALSO"
-getinfo(1), lookamb(1), oconv(1), pdfblur(1), pfilt(1), pinterp(1), pmblur(1),
-printf(3), ra_rgbe(1), rad(1), rtrace(1), rvu(1)
+getinfo(1), lookamb(1), mkpmap(1), oconv(1), pdfblur(1), pfilt(1), 
+pinterp(1), pmblur(1), printf(3), ra_rgbe(1), rad(1), rpiece(1), rtpict(1), rtrace(1), rvu(1)