A series of parameters can be set for isovist calculation. Each parameter is controlled by a slider in the isovist analysis menu as follows:

• Isovist sweep (angle of view).
• Direction (heading that the isovist is ‘looking’ in).
• Far rim (how far the isovist can ‘see’).
• Near rim (an internal horizon that sets the nearest visible edges of the isovist). 

Setting a parameter affects all latter field analysis calculations and automatically resets all analysis. 

Below: Editing the parameters of isovists in Mies’ Barcelona Pavilion