On the hardware side, if you have switchable graphics make sure to associate the high performance graphics card (usually the dedicated one - NVIDIA or AMD chip) with DSM. Or, enable that card prior to launching DSM.
In the Graphics performance options group in the Popular screen in DesignSpark Mechanical Options, select a higher number Rendering quality.
You can choose any number between 1 and 7, where 1 is the lowest rendering quality and 7 is the highest, but be aware that a higher setting may impact performance.
Click the Recalculate Rendering button to force recalculation of all surface and line rendering.