System and method for generating planar section 3D shape representations

1. A system for generating one or more planar sections to represent a three-dimensional model using a fluid stroke-based workflow, the system comprising one or more processors and a computer-readable memory, the computer readable memory having computer readable instructions stored thereon, which when executed by the processor are configured to provide:

a user interface unit configured to receive:

user input, the user interface unit further operable to detect a user input of a continuous stroke defined by a starting point and an ending point; and

a three dimensional model input by the user; and

a generating unit in communication with the user interface unit, the generating unit configured to receive the continuous stroke and generating:

a planar section, along a first plane, having a boundary including the starting point and the ending point; and

in response to user input of a subsequent stroke with a subsequent starting point inside the boundary of a first planar section, generating a subsequent planar section along a second plane, the second plane substantially orthogonal to the first plane,

wherein the user interface unit is in communication with a display device, the user interface unit is further configured to present to a user each generated planar section as being frontoparallel with the display device, and automatically rotating the view with respect to the display device such that the subsequent planar section will be displayed as frontoparallel with the display device, and

wherein the generating unit is further configured to determine a boundary surface of the three dimensional model and to generate and present to the user, for each view of a plane defined by a planar section, guide curves to serve as a guide for planar section generation, the guide curves resulting from an orthogonal projection onto the plane by a non-planar silhouette contour of the three dimensional model defined by any points of the boundary surface whose normal are orthogonal to the plane's normal.

2. The system of claim 1 , wherein the generating unit generates each planar section symmetrically about the corresponding stroke.

3. The system of claim 1 , wherein the system further generates a dead zone around a stroke, the user interface unit configured to receive user input within the dead zone to determine the shape of the boundary of the planar section.

4. The system of claim 1 , wherein the user interface unit is further configured to generate a visual representation of structural stress exhibited by the planar section representation.

5. The system of claim 1 , wherein:

the user interface unit is configured to receive from the user a command for a replication operation and an input planar section for the replication operation; and

the generation unit is configured to generate one or more further planar sections that are replications of the input planar section.

6. The system of claim 5 , wherein the replications are coplanar with the input planar section.

7. The system of claim 5 , wherein the replications are not coplanar with the input planar section.

8. The system of claim 5 , wherein the replications are scaled versions of the input planar section based on cross-sectional widths of a root planar section at intersections with the input planar section and the replications.

9. The system of claim 1 , wherein any point of a user's sketched stroke within a predetermined distance of any guide curve is translated to the nearest point on that guide curve.

10. The system of claim 1 , wherein the generating unit is further configured such that in generating the guide curves only points of the boundary surface within a predetermined distance of the plane are projected onto the plane.