fiiRay is open-source physically based 3D renderer that can be used to create photorealistic images. Pythonscript add-on for Blender 2.50 can be used to export scenes for fiiRay. fiiRay is still in development and current version is not stable.
This software can be used for relief and normal maps calculation by 3D sculptors and designers. Reliefer can be called from Blender by means of Pythonscript. It's a GPU-based visual computing application so requres OpenGL 2 compitable video subsystem.