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The image_generator directory contains the following files:

prepare_vs.sh prepares the cloud server to save image files to an object store and builds the Dockerfile.

image_generator.dockerfile builds the imgen image.

get_skies.py reads a YAML input file and generates an SSC that Stellarium executes. The SSC is build from random locations sampled from the spatial-temporal grid defined in the YAML file.

get_skies.sh and get_skies_grid.py are deprecated but is kept for reference. This files contains code to generate images based on a spatial-temporal grid.

get_skies_helper.py contains functions used by get_skies.py.

screenshot.sh runs the image generation routine from the docker container.

default_cfg.ini is a replacement for Stellarium's configuration file. This turns off several modules that slow the image generation process.

ssc_gen.yml is a sample input file.

Note: The image generator must be run on a server with a GPU. We assume that the virtual server is running Ubuntu 18.04 and is already provisioned with Docker and s3fs.

Note: The output of the image generator need not be placed in an object store. The steps below can be adapted to direct the images to local storage.

• After pulling the repository on the virtual server, create a credentials file with vi credentials to allow access to object storage. The credentials file should contain a single line with <api_key>:<secret>.

• Next edit the prepare_vs.sh script such that it contains the user's object store information, and run script to build the image generator Docker image and link the mountpoint to the appropriate S3 bucket.

chmod +x prepare_vs.sh
./prepare_vs.sh

• Verify that the imgen image is built by calling docker images.

• Edit the ssc_gen.yml file to configure the maximum and minimum latitudes, longitudes, and times that will be rendered.

• Create an imgen container instance with access to the host's mountpoint. docker run --name <name> -dit -v /<mountpoint>:/<mountpoint> imgen

• Copy the YAML file to the container. docker cp ssc_gen.yml <name>:/

• Run the image generator and monitor progress. docker exec <name> ./screenshot.sh

The steps above can be automated further as needed. Multiple instances of the image generator container can be run on the same server to speed the process.