--- ray/doc/man/man1/rcomb.1	2024/05/07 17:15:31	1.7
+++ ray/doc/man/man1/rcomb.1	2025/04/04 18:06:48	1.13
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rcomb.1,v 1.7 2024/05/07 17:15:31 greg Exp $"
+.\" RCSid "$Id: rcomb.1,v 1.13 2025/04/04 18:06:48 greg Exp $"
 .TH RCOMB 12/5/2023 RADIANCE
 .SH NAME
 rcomb - combine and convert matrices a row at a time
@@ -11,6 +11,8 @@ rcomb - combine and convert matrices a row at a time
 ][
 .B \-f[afdc]
 ][
+.B "\-n nproc"
+][
 .B "\-f file"
 ][
 .B "\-e expr"
@@ -141,12 +143,11 @@ or
 is specified for an input picture or the
 .I "-fc"
 option is given, the output will be written as a RGBE or XYZE picture.
-Note that conversion from a float or RGBE color space applies a conversion
+Note that conversion from a float or RGBE color space applies an efficacy factor
 of 179 lumens/watt (for CIE or melanopic output) or 412 (for scotopic output),
-and the reverse happens for conversion from XYZE input to RGB or RGBE output.
+and the inverse happens for conversion from XYZE input to RGB or RGBE output.
 Lower case versions of all these components are also supported, the only
-difference is that the aforementioned efficacy factors
-will be left out of the conversion.
+difference being that the efficacy factors are ignored.
 .PP
 If a matrix or picture file path is given to the
 .I \-c
@@ -250,11 +251,18 @@ The
 .I \-w
 option turns off warnings about divide-by-zero and other non-fatal
 calculation errors.
+.PP
+The
+.I \-n
+option specifies how many execution processes to employ,
+which may improve performance on multi-core architectures,
+especially for matrix multiplication
+and complex operations on long input rows.
 .SH EXAMPLES
-To convert two hyperspectral inputs to RGB color space,
+To convert two hyperspectral pictures to RGB color space,
 average them together, and write them out as a RADIANCE picture:
 .IP "" .2i
-rcomb -C RGB -s .5 img1.spc -s .5 img2.spc > avg.hdr
+rcomb -C RGB -s .5 img1.hsr -s .5 -fc img2.hsr > avg.hdr
 .PP
 Divide one set of matrix elements by the Euclidean sum of two others:
 .IP "" .2i
@@ -264,9 +272,9 @@ inp2.mtx inp3.mtx > out.mtx
 Compute the absolute and relative differences between melanopic and photopic values
 in a spectral image:
 .IP "" .2i
-rcomb -fa -C MY -e "abs(x):if(x,x,-x)"
+rcomb -C MY -e "abs(x):if(x,x,-x)"
 -e "co(p)=select(p,abs(ci(1,1)-ci(1,2)),(ci(1,1)-ci(1,2))/ci(1,2))"
-input_spec.hsr > compare.mtx
+input_spec.hsr -fa > compare.mtx
 .PP
 Concatenate a spectral flux coefficient matrix with a spectral sky
 matrix to compute a set of melanopic lux values:
@@ -331,6 +339,14 @@ is not supported in
 .I rcomb,
 and should instead be handled by
 .I pfilt(1).
+.PP
+Similar to
+.I rmtxop,
+all calculations are peformed internally using 32-bit floating-point,
+so there is little benefit in either reading or writing 64-bit double
+data.
+This may be overridden at compile time using the macro
+"-DDTrmx_native=DTdouble".
 .SH BUGS
 The
 .I rcomb
@@ -341,6 +357,6 @@ circumstances where it would make sense to.
 Greg Ward
 .SH "SEE ALSO"
 dctimestep(1), icalc(1), getinfo(1), pcomb(1), pfilt(1),
-ra_xyze(1), rcalc(1),
+pvsum(1), ra_rgbe(1), ra_xyze(1), rcalc(1),
 rcollate(1), rcontrib(1), rcrop(1), rfluxmtx(1), 
 rmtxop(1), rtpict(1), rtrace(1), vwrays(1)