Monday, 30 January 2012

Maya Alembic Export

Whilst this blog is mainly concerned with setting up alembic maya export within the University network, most of this is also applicable to other systems. You just need to change all the paths to the corresponding ones on your system.

First you need to download and build your alembic maya plugins. These come as part of the Alembic package and you should follow the build instructions. Once everything is built you will have a directory within the source tree called maya/plug-ins.

On the University system this is in the directory /public/bin/alembic/maya/plug-ins and you should see the two plugins AbcExport.so  AbcImport.so

University Setup
In the root of your home directory (type cd and press enter) execute the following commands

cd
mkdir MayaPlug
mkdir MayaScript
cp /public/bin/alembic/maya/plug-ins/* ~/MayaPlug
This will copy the Alembic plugins into a pre-defined directory which we will tell maya to search when starting up. This is controlled by the file Maya.env. Again the location of this file will differ depending upon the install, but in the University this is located here $HOME/maya/2011-x64/ If this file doesn't exist in the directory you can create your own using the following command
cd $HOME/maya/2011-x64/
touch Maya.env
gedit Maya.env
This will open the file and allow us to edit the maya environment variables used when maya starts. We need to add to this file the following
MAYA_PLUG_IN_PATH=/home/jmacey/MayaPlug
MAYA_SCRIPT_PATH=/home/jmacey/MayaScripts
PYTHONPATH=MAYA_SCRIPT_PATH
In the above example you will need to change the /home/jmacey to your own home directory path. This will then setup two areas that maya will search when looking for plugins ( $HOME/MayaPlug ) and scripts ( $HOME/MayaScript ) when you now start maya you should get the following list when opening the Menu Windows->Settings / Preferences -> Plugin-Manager
You should now see the AbcExport.so ( this screen shot from my mac is different as it uses a .bundle) and AbcImport.so. If you click on the Loaded button it will load the plugin and you should be able to type AbcExport -h in the Mel tab of the script editor as shown below
For more info on this read the blog post here. As the command line is a little bit complex, I decided to create a simple GUI to make life easier. The main design for this came from the output of AbcExport -h and all the options printed in the help that actually work have been translated into gui items.

AlembicExport.py

The AlembicExport.py script can be downloaded from here and it should be saved in the $HOME/MayaScripts directory.

When using the script you will need to select all the geometry you wish to export (if you select all Alembic will attempt to export all it can ) and type the following in the python script editor
from AlembicExport import *
AlembicExport()
This will give you the following GUI
The current frame range is selected and by default uv's and normals will be exported. Other options are available and you should read the AlembicExport help for more details. 

The actual alembic jobstring and command line is placed in the job string text field so you can copy this if you wish to use the command line at a later date.

Code outline
The code is fairly self explanatory, however I will outline a couple of areas.
First we check to see if the AlembicExport plugin is installed. This is done with the following code
# check to see if plugin is loaded
plugs=cmds.pluginInfo( query=True, listPlugins=True )
if "AbcExport" not in plugs :
  print "AbcExport not loaded please load it"
To build up the jobstring for the actual export we use the following code
jobstring="AbcExport "
if self.verbose == True :
  jobstring+=" -v "
jobstring+="-j \" -fr %d %d -s %d" %(self.start,self.end,self.steps)
.....
This will build up a complete export command which we will then execute using the eval command as follows
mel.eval(jobstring)

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