A Grasshopper definition consists of a series of components connected by wires. This image shows a typical definition with components and wires:

 

Grasshopper definitions are always read from left to right.

Definitions always have a mechanism for input. Input can be in the form of Rhino objects, or it can be in the form of numbers. In the example shown above, input is provided by adjusting the three number sliders.

Reading from left to right, input feeds into components along wires. Components typically perform some action, which could involve performing calculations or constructing objects in Rhino. In the example shown above, the Rectangle component creates a rectangle in the Rhino modeling environment, using as input the “X Size” and “Y Size” numbers set by the number sliders. Similarly, the BoxRec component creates a rectangular box in Rhino, using as input the rectangle constructed by Rectangle, and the “Height” number set by the number slider.

Thus, Grasshopper definitions have output which is typically in the form of potential Rhino objects. These potential Rhino objects become actual Rhino objects only when Grasshopper’s Bake command is applied within the definition. To Bake a definition, right-click on a component’s output node (on its right side), and select Bake.