Lambda Converters

A project containing several AWS Lambda file converters.

Building Lambda Functions

Underlying Technologies

These lambda functions depend heavily on the Open Cascade Community Edition and PythonOCC.

Environment

This project contains pre-compiled binaries in oce and pythonocc. These binaries were compiled on an AWS Linux instance, but they also run on Ubuntu 16.04.

You will have trouble if you try to use these binaries on a Mac. Unfortunately, there is currently no solution for compiling PythonOCC libraries from source on an OSX machine (at least in my experience).

build.py

The build.py script is meant to automate the build process for these lambda functions. You can rebuild a particular lambda by running ./build.py -d <lambda_directory>. The build script expects to find two files within a lambda's directory.

libs_oce.txt - a list of OpenCascade libraries to copy into the lambda's lib directory.
libs_pythonocc.txt - a list of PythonOCC libraries to copy into the lambda's OCC directory.

The build script will also copy the files listed in common_files.txt into the root of the lambda's directory.

Tests

See the step_to_stl directory as an example. It helps to have a test.sh script in the lambda's root directory so that the LD_LIBRARY_PATH environment variable can be set before running any unit tests.

Troubleshooting

If you see

TypeError: in method 'StlAPI_Writer_Write', argument 3 of type 'char const *'

or something complaining about char const * arguments, these are a result of using SWIG with OpenCascade. To fix such an issue, pass your string-like objects to PythonOCC functions using Python's str function.

Example:

status = step_reader.ReadFile(str(filename))

Rebuilding Binaries

The following steps took place on an AWS EC2 instance running AWS Linux.

The steps below assume that the project will be built at /home/ec2-user/lambda_converters.

Copy libGLU

AWS Lambda functions' runtime environment does not contain libGLU, so we need to provide a copy of it.

Find libGLU.so somewhere on your system (or install it, then find it) and copy it /home/ec2-user/lambda_converters/lib.

Compile OCE

cd /home/ec2-user/lambda_converters
git clone git@github.com:tpaviot/oce.git
cd oce
git fetch origin
git checkout -b 0.16.1 origin/OCE-0.16.1
mkdir build && cd build
cmake -DOCE_INSTALL_PREFIX=/home/ec2-user/lambda_converters/oce ..
make
make install/strip

Compile Python OCC

Install Dependencies

sudo yum install swig

Install PythonOCC Core

cd /home/ec2-user/lambda_converters
git clone git://github.com/tpaviot/pythonocc-core.git pythonocc
cd pythonocc
mkdir cmake-build && cd cmake-build
cmake -DOCE_INCLUDE_PATH=/home/ec2-user/lambda_converters/oce/include/oce \
-DOCE_LIB_PATH=/home/ec2-user/lambda_converters/oce/lib ..
make

semixor/lambda_converters