Paul Taele's Research Blog: June 2010

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Random Stuff:

Simple Way to Generate PDF File from LaTeX file:

Initial observations of users' sketched trusses.

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Mechanics Sketch Research:

Observations of Sketched Trusses, Pt. 1:

Initial observations of users' sketched trusses.

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User Sketched Data of Truss 1-2:

User sketched data for Truss 1-2, which is a truss with 1 layer and contains 2 upward-pointing triangles in the top layer.

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User Sketched Data of Truss 1-3:
User sketched data for Truss 1-3, which is a truss with 1 layer and contains 3 upward-pointing triangles in the top layer.

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User Sketched Data of Truss 2-2:

User sketched data for Truss 2-2, which is a truss with 2 layers and contains 2 upward-pointing triangles in the top layer.

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Observations of Sketched Trusses, Pt. 1

The most recent screencasts of sketched data contained examples from three sample truss structures. The sample truss structrues consisted of the following:

1-layer truss with 2-triangle width
1-layer truss with 3-triangle width
2-layer truss with 2-triangle width

Based on the collected screencasts of the most recent study, here are some observations.

1) Trusses are not built directly from triangles.

Triangles in isolation are three lines uniquely connected at their endpoints. When pointed upward, the triangle forms part of supports in civil and mechanical engineering.
For sketched trusses though, the collected data do not show any instance of triangles being drawn. Instead, shapes of triangles are drawn indirectly as part of the larger truss structure.
Specifically, triangular shapes are formed where at least one line in the triangular shape is not connected with an endpoint from the other two lines. Stated another way, a non-endpoint of at least one line is coincident with the endpoint of one of the other two lines in the triangular shape.

2) Initially building trusses from a trapezoid is common.

In sketching trusses, there is a common preference for starting the sketch of trusses by starting with the outer trapezoid shape. This behavior isn't uniformly shared, but there is a large consensus for it.
This behavior is more readily apparent for multi-layer trusses, where users probably start off with the trapezoid shape as a reference for sketching the rest of the truss structure.

3) Sloped lines within a truss that cross multiple layers are common.

Within the outer trapezoid shape of multi-layer trusses exists two kinds of lines:

horizontal lines
sloped lines

While horizontal lines serve as the border between these layers, sloped lines are visually filler that serve as lines that are parallel to the non-parallel-sides of the outer trapezoid shape.
In order to decrease the number of directional changes of sketching, many of the users often draw sloped lines that cross multiple layers. This behavior is apparent for 2-layers, but it remains to be seen if this behavior persists for higher number of layers.