This page describes how to use GBRUNION command line options to convert a few Gerber files to GDSII with layer mapping.

It can be done along with our gdsfilt as explained below. Please note that the Gbrunion can only generate single layer output so three Gerber files, for example, will have to be three GDSII outputs.
From here the methodology to follow is to use gdsfilt and map each output to a desired layer, and blend all outputs into a single GDSII file if it is desired to have only one output file.

Below is a three stage example which creates a multi layered GDSII output file:

(1) Generate a GDSII file for each Gerber file
    [5v.gds, gnd.gds, and top.gds are created from three different Gerber files]

[5v.art ==> 5v.gds]
"c:\wcad\gbrvu\gbrunmgr.exe" "d:\temp\5v.art"  "-out:d:\temp\5v.gds" "-wdir:d:\temp" -outputtype:gds_stream -sizingvalue:0.000 -smoothingvalue:0.005 -maxpoints:2000 -arcres:45.000 -silent -singledlg

[gnd.art ==> gnd.gds]
"c:\wcad\gbrvu\gbrunmgr.exe" "d:\temp\gnd.art" "-out:d:\temp\gnd.gds" "-wdir:d:\temp" -outputtype:gds_stream -sizingvalue:0.000 -smoothingvalue:0.005 -maxpoints:2000 -arcres:45.000 -silent -singledlg

[top.art ==> top.gds]
"c:\wcad\gbrvu\gbrunmgr.exe" "d:\temp\top.art" "-out:d:\temp\top.gds" "-wdir:d:\temp" -outputtype:gds_stream -sizingvalue:0.000 -smoothingvalue:0.005 -maxpoints:2000 -arcres:45.000 -silent -singledlg

(2) Map outputs to desired layers [All output is initially on layer one]

[Map 5v layer one to layer five.]
c:\wcad\gbrvu\gdsfilte.exe d:\temp\5v.gds  d:\temp\5v_lyr1to5.gds  = -unixcmdline -lyr1:5

[Map gnd layer one to layer six.]
c:\wcad\gbrvu\gdsfilte.exe d:\temp\gnd.gds d:\temp\gnd_lyr1to6.gds = -unixcmdline -lyr1:6

[Map top layer one to layer seven.]
c:\wcad\gbrvu\gdsfilte.exe d:\temp\top.gds d:\temp\top_lyr1to7.gds = -unixcmdline -lyr1:7

(3) Blend all mapped GDSII output into one file
[Blend all three layer mapped files into one file called blend.gds]

c:\wcad\gbrvu\gdsfilte.exe d:\temp\5v_lyr1to5.gds d:\temp\blend.gds = -unixcmdline -blend d:\temp\gnd_lyr1to6.gds d:\temp\top_lyr1to7.gds


GDSFILT USAGE--

The gdsfilte.exe usage is as follows:

gdsfilte.exe inputfile outputfile topstr [options]

   outputfile is the GDS output file name.

   only topstr and its dependents are output. if topstr is '=' then, the structure with the deepest tree is selected.

   options can be some of

   -unixcmdline      Perform GDSII scan (necessary in this context)
   -lyrM:N,...       Remap layer range M to N.
   -dtpM:N,...       Remap datatype range M to N.
   -mapM%N:m%n,...   Remap layer:datatype(s) M:N to m:n.
   -blend f1 f2 ...  fn  blend files f1, f2 ... fn with inputfile.