The Plant 3D SDK is formatted in the same way as the ObjectARX SDK, therefore, it is possible to simply overlay the Plant 3D SDK onto a pre-installed ObjectARX SDK. When developing applications, you will be working with both the ObjectARX SDK for AutoCAD and the Plant SDK. To successfully utilize the APIs documented in this guide, developers should be familiar with ObjectARX and the. Plant 3D-only interfaces are identified in the Plant SDK reference guide included in the SDK. To create programs that will run on AutoCAD P&ID, do not reference Plant 3D-only interfaces. In the Plant SDK, the AutoCAD® P&ID API is a subset of the Plant SDK. The Plant SDK includes an Application Program Interface (API) to extend the AutoCAD® API and provide software developers with a means to query and control P&ID schematic and project information, and the AutoCAD Plant 3D model. Architecture, Engineering and Construction.