What is the first step in creating a 3D model using SolidWorks?

Creating a sketch is the foundational step in developing a 3D model using SolidWorks because it establishes the two-dimensional representation of the part or feature you intend to create. Sketching allows you to define the geometry, shape, and size of the model using various sketch entities, such as lines, arcs, and circles. Once you have a sketch, you can then use it as a basis for 3D features through operations like extruding or revolving, transforming the flat shape into a solid object.

The other options involve subsequent stages or aspects of the modeling process. Defining material properties comes after the 3D model is created, as it involves specifying the material characteristics of the model for simulation and analysis. Rendering takes place after the model is fully defined, allowing for visualization and presentation, and setting up assemblies pertains to combining multiple parts into a coherent structure, which happens later in the design workflow.