Fusion of Visual Channels - Scientific Visualization: Uncertainty, Multifield, Biomedical, and Scalable Visualization - page 114

Geometric Channels provide means to differentiate visual entities by making use
of their different geometric properties, including

• Size/length/width/height/depth/thickness/area/volume

• Orientation

• Shape

• Curvature

• Smoothness

Optical Channels provide means to differentiate visual entities by making use of
different optical effects. Many of such effects rely extensively on perceptual inter-
pretation. For example, different shading effects, which can be used to encode high-
level concepts such as materials, are perceived through the changes of brightness
and colours resulting from some rendering algorithms. In visualization, motion can
be depicted explicitly as well as implicitly. The former includes both first-order and
second-order motion perception, while the latter makes use of static depiction, such as
motion blur patterns. Different visual effects in the class of optical channels include:

• Intensity/brightness

• Colour/hue/saturation

• Opacity/transparency

• Line style/surface texture/volume texture

• Shading and lighting effects/halos

•

Shadow

•

Photographic effects such as focus, blurring, optical distortion

• Implicit motion/motion blur patterns

• Explicit motion/animation/flicker

Relational Channels provide means to differentiate visual entities by making use
of depictions of different relations. There are two main types of relations. Spatial
relationships , such as distance , depth , and density , convey the difference between
two visual entities through their geometric or geographic relationships with other
entities in the scene, or the perceived spatial relationship with the viewer. Topological
relationships , such as connectivity , hierarchy , and closure , convey the difference
between two visual entities through the different structures associated with them, or
their different roles in a shared structure. Some of such effects rely on perceptual
interpretation, while many rely extensively on cognitive interpretation. For example,
depth is a complex perceptual phenomenon because it may result from different
visual channels. The perception of depth can be caused by explicit binocular cues
(e.g., stereo vision), or implicit monocular cues (e.g., perspective and occlusion).

• Connection/edge

• Node/internal node/terminator

• Inside/outside/enclosure/boundary

• Distance/displacement/offset

• Closure/opening