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Integral versus separable shape attributes
The issue of integral versus separable dimensions [War00, Wil05] is
related to the like versus like issue. Integral dimensions are perceived
holistically not independently. Early experiments creating shapes based on
morphologies of curved versus angular corners did not result in glyphs
understood as having four separate attributes (Fig 3.29), but were rather
understood as simply being different (Fig. 3.27). With the Gas Survey
trumpet glyphs visualization (Fig. 3.24 and 3.27), some of the visual
entities are very separable, such as the terminator or angle which can be
understood readily as separate from the rest of the glyph. The top line has
both curvature and line styles which are separable, but presumably not as
perceptually separable as the terminator:
Fig. 3.29.
The four separate attributes defining the shapes on the left (i.e. corners
round or square) are not as easily distinguishable as the four different attributes
defining the shapes on the right - curvature, serif, angle, edge type.
The issue regarding concavity discussed earlier may be an issue of
separable versus integral, and the particular use of concavity in the
experiment is integral, therefore making it difficult to visually parse
concavity separately.
Connotative shape mappings
Most of the experiments arbitrarily assigned a data attribute to a shape
attribute. Previous researchers recommended connotative mappings
between data variables to visual attributes (e.g. [Bra97], [War00]). The
connotative mapping data of a shape attribute is largely unexplored
(except for pictographs, which are direct representations of a data
category). One experiment considered a connotative use of shape
attributes. A set of Venn and Euler diagrams was created, where the
underlying Venn or Euler diagram shows logical set memberships. The
size of an overlaid circle indicates the number of items within a particular
set combination, and external spikes around the perimeter of each circle
indicate set membership (Fig. 3.30).
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