Sketch

Sketches are presently usually created and edited using the graphical sketch editor interface. The sketch editor interface should display whenever a sketch is created via the Create menu or whenever an existing sketch primitive is selected for editing.

That said, it is possible using the low-level database I/O "get" and "put" commands to create and edit a sketch. Those commands are actually what the GUI-based sketch editor uses under the hood.

One of the better ways to describe the format of the sketch primitive is with an example. Here's a mildly detailed sketch that contains lots of points and several entity types. Shown in following is a case where we have a simple sketch named "mysketch". If you run the "get" command, you can see the overall structure:

mged> get mysketch

The result is:

sketch V {0 0 -4.999999999999999646464397e-40} A {1 0 0} B {0 1 0} VL { {0.59800664451827234557868 -4.674418604651163100527356} {2.501661129568105934595224 -1.833887043189368792894811} {6.259136212624585304808988 -3.109634551495016552280504} {2.581395348837209002823556 -3.209302325581395720632827} {5.830564784053156479615154 -5.571428571428572062984586} {5.521594684385382478808424 -1.764119601328903774728474} {2.531561461794019862736604 -0.9966777408637871316088308} {0.1594684385382059976787872 0.2691029900332225777148665} {-2.720930232558139483245441 -1.495016611295681085991305} {1.764119601328903774728474 -1.016611295681063120710519} {0.239202657807309121418271 -2.730897009966777755352041} {1.9634551495016612232547 -2.501661129568106378684433} {-1.265780730897009931368302 -2.611295681063122930964937} } SL { { line S 0 E 1 } { carc S 2 E 1 R -1 L 0 O 0 } { bezier D 3 P { 1 3 4 5 } } { carc S 5 E 6 R 1.644755298192071224505639 L 0 O 0 } { line S 6 E 7 } { bezier D 6 P { 7 8 9 10 11 12 0 } } }

Most of that is floating point conversion goo of course, but it boils down to what is shown in following with a V position, AxB vectors to scale/orient the sketch, a VL list of 2D vertices, and then any number of SL segment lists for lines, arcs, and bezier curves. Note that the 'sketch' prefix is not the name of the primitive but, rather, its type.

sketch
V {0 0 -4.999999999999999646464397e-40}
A {1 0 0}
B {0 1 0}
VL {
   {0.59800664451827234557868 -4.674418604651163100527356}
   {2.501661129568105934595224 -1.833887043189368792894811} 
   {6.259136212624585304808988 -3.109634551495016552280504}
   {2.581395348837209002823556 -3.209302325581395720632827}
   {5.830564784053156479615154 -5.571428571428572062984586}
   {5.521594684385382478808424 -1.764119601328903774728474}
   {2.531561461794019862736604 -0.9966777408637871316088308}
   {0.1594684385382059976787872 0.2691029900332225777148665}
   {-2.720930232558139483245441 -1.495016611295681085991305}
   {1.764119601328903774728474 -1.016611295681063120710519}
   {0.239202657807309121418271 -2.730897009966777755352041}
   {1.9634551495016612232547 -2.501661129568106378684433}
   {-1.265780730897009931368302 -2.611295681063122930964937}
}
SL {
   { line S 0 E 1 }
   { carc S 2 E 1 R -1 L 0 O 0 }
   { bezier D 3 P { 1 3 4 5 } }
   { carc S 5 E 6 R 1.644755298192071224505639 L 0 O 0 }
   { line S 6 E 7 }
   { bezier D 6 P { 7 8 9 10 11 12 0 } }
}

You can run the 'l' (ell not one) command on an existing sketch to get a descriptive summary. For example, S and E reference the corresponding VL vertex starting and ending point respectively.

mged> l mysketch 
mysketch:  2D sketch (SKETCH)
        V = (0 0 -0),  A = (1 0 0), B = (0 1 0)
        13 vertices
        Vertices:
         0-(0.598007 -4.67442) 1-(2.50166 -1.83389) 2-(6.25914 -3.10963)
         3-(2.5814 -3.2093) 4-(5.83056 -5.57143) 5-(5.52159 -1.76412)
         6-(2.53156 -0.996678) 7-(0.159468 0.269103) 8-(-2.72093 -1.49502)
         9-(1.76412 -1.01661) 10-(0.239203 -2.7309) 11-(1.96346 -2.50166)
         12-(-1.26578 -2.6113)

        Curve:
                Line segment (0.598007 -4.67442) <-> (2.50166 -1.83389)
                Full Circle:
                        center: (2.50166 -1.83389)
                        point on circle: (6.25914 -3.10963)
                Bezier segment:
                        degree = 3
                        starts at (2.50166 -1.83389)
                        ends at (5.52159 -1.76412)
                Circular Arc:
                        start: (5.52159, -1.76412)
                        end: (2.53156, -0.996678)
                        radius: 1.64476
                        curve is counter-clock-wise
                        center of curvature is right of the line from start point to end point
                Line segment (2.53156 -0.996678) <-> (0.159468 0.269103)
                Bezier segment:
                        degree = 6
                        starts at (0.159468 0.269103)
                        ends at (0.598007 -4.67442)

You can create one by writing out the sketch as one long Tcl line but instead of "get", you'd use put to create/update a sketch. Example box:

mged> put mysketch2 sketch V {0 0 0} A {1 0 0} B {0 1 0} VL { {0 0} {1 0} {1 1} {0 1} } SL {
  {line S 0 E 1} {line S 1 E 2} {line S 2 E 3} {line S 3 E 0} }

Example box with big rounded edges (barbell shape):

mged> put mysketch3 sketch V {0 0 0} A {1 0 0} B {0 1 0} VL { {0 0} {1 0} {1 1} {0 1} } SL {
  {line S 0 E 1} {carc S 1 E 2 R 1 L 0 O 0} {line S 2 E 3} {carc S 3 E 0 R 1 L 0 O 0} }

There is of course plenty of room for improvement when it comes to creating, editing, and managing sketches and sketch data. Contributions are always welcome!