SOFiPLUS 17.1 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The most popular versions of the program 18.1 and 17.1.
The software lies within Photo & Graphics Tools, more precisely 3D Design. The actual developer of the software is SOFiSTiK AG. We cannot guarantee that the program is safe to download as it will be downloaded from the developer's website. Before launching the program, check it with any free antivirus software.
From the developer:
SOFiPLUS is SOFiSTiK's standard pre-processor. Based on AutoCAD 2010 the program takes full advantage of the enhanced AutoCAD modelling-technology enabling the engineer to generate almost any FE-structure - from simple slabs to complicated freeform-surfaces. SOFiPLUS can be purchased as a pure add-on to AutoCAD or included with an integrated AutoCAD 2009-OEM engine
You may want to check out more software, such as Win4D Advance or FRED Optical Engineering Software, which might be similar to SOFiPLUS.