--- ray/doc/man/man1/rpict.1	2018/03/20 02:40:38	1.23
+++ ray/doc/man/man1/rpict.1	2020/05/19 16:00:58	1.26
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rpict.1,v 1.23 2018/03/20 02:40:38 greg Exp $"
+.\" RCSid "$Id: rpict.1,v 1.26 2020/05/19 16:00:58 greg Exp $"
 .TH RPICT 1 2/26/99 RADIANCE
 .SH NAME
 rpict - generate a RADIANCE picture
@@ -211,10 +211,10 @@ 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
@@ -464,8 +464,10 @@ Normally, indirect illuminance values are kept in memo
 lost when the program finishes or dies.
 By using a file, different invocations can share illuminance
 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).
@@ -595,14 +597,10 @@ 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. In conjunction with the
-.I \-n
-option, this is the cache size
-.I per parallel process. 
-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.
+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,
@@ -666,8 +664,8 @@ 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