Grasshopper Basic Functionality
The following screengrabs are using grasshopper 06.0059 which can be downloaded here. The grasshopper primer and ‘algorithimic modelling for grasshopper’ are also both useful resources, and can be found through the grasshopper3d site.
referencing rhino geometry
Generally the quickest way to start modeling in grasshopper is by referencing some objects that you have already made with rhino. You can then operate on these objects in grasshopper (e.g. loft, divide, move). Any changes you make to the objects in rhino will be picked up by grasshopper and ‘flow’ through your definition, allowing you to quickly see an updated version of your model.
Once your rhino object has been ‘set’ to the grasshopper component, you can start building your definition. You will find grasshopper has most of the same modeling tools as rhino. Unlike rhino however, grasshopper has a history. Any modifications you make to the inputs will update the output.
5 Rhino curves are referenced in to grasshopper and connected to a loft component. This produces the same result as lofting the curves using the loft command in rhino. The difference is that any change you make to the curves in rhino will update the loft. This allows you to effectively sculpt your model. 
