For us, the first step to constructing an inflatable is designing the 3D model using a CAD program like AutoCAD or Solidworks. Using artistic license, we added a third leg to make the robot more stable. Further, inflatable shapes tend towards a sphere when inflated, so some allowance must be made. For example, to prevent the legs from splaying we pointed them inwards.
With the model in hand, we use Rhino (available
as a Work In Progress download for Mac) to unroll "developable" surfaces which lie flat and can be sewn together into the original model.
Next, we need to add 10 mm seam allowances and arrange the parts onto printable pages. Using Illustrator or Inkscape, we can take the DXF output of Rhino and use 'Path Offset' to add seam allowance. The panels with allowances can be arranged manually to fit on printable pages. This method works well but can be really tedious with many panels.
As an experiment, we read the output of Rhino and programmatically added seam allowances and nested the parts on paper stock.