Next week we will start with a very basic introduction to grasshopper. Grasshopper is a plug-in that works alongside Rhino 5 and is available for free.
Windows users can download the plug-in here and follow the installation instructions.
http://www.grasshopper3d.com/page/download-1
Mac users need to work with the Rhino 6 WIP, which is a pre-release version of Rhino that is available to owners of Rhino 5 for mac. Grasshopper will run natively in Rhino 6, so for now Mac users must download and install this pre-release version of Rhino, which is still in development and thus is missing some features and may have stability issues. See more here:
http://www.grasshopper3d.com/notes/index/show?noteKey=Will_Grasshopper_work_on_the_Mac%3F