Software :: Finding A 3D Composing And Rendering App?

I am looking for 3D composing and rendering software which has a text-based scene file format. I saw that there was such software that was free open source (e.g. GPL or BSD licensing) a couple years ago, but forgot what that was. I looked at Blender just now, but its format is binary.

The purpose for this is to, in step 1, compose a scene that acts as a template, and in step 2, generate additional elements for the scene, or modify the scene, with specific data used to control those elements. This data will change each time step 2 is done. The purpose is to do a 3D image of certain measured source data. And step 2 needs to be doable w/o the GUI interface so it can be run on servers. Step 2 will be done w/o any human activity (e.g. an hourly cron job, for example).