This paper introduces six graphical principles for 30 network displays. These are justified with examples from GraphVisualizer3D, a system developed by the authors to investigate the problems of 30 visualization of information networks. GraphVisualizer3D enables the exploration of sulface color, surface texture, object shape, arc shape and labeling conventions

Franck, Glenn

Ware, Colin

English

University of New Hampshire

University of New Hampshire
University of New Hampshire Scholars' Repository
Center for Coastal and Ocean Mapping Center for Coastal and Ocean Mapping
10-1994
Representing Nodes and Arcs in 3D Networks
Glenn Franck
University of New Brunswick
Colin Ware
University of New Hampshire, Durham, colin.ware@unh.edu
Follow this and additional works at: https://scholars.unh.edu/ccom
Part of the Computer Sciences Commons, and the Oceanography and Atmospheric Sciences and
Meteorology Commons
This Conference Proceeding is brought to you for free and open access by the Center for Coastal and Ocean Mapping at University of New Hampshire
Scholars' Repository. It has been accepted for inclusion in Center for Coastal and Ocean Mapping by an authorized administrator of University of New
Hampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu.
Recommended Citation
Franck, G.; Ware, C., "Representing nodes and arcs in 3D networks," in Visual Languages, 1994. Proceedings., IEEE Symposium on ,
vol., no., pp.189-190, 4-7 Oct 1994 doi: 10.1109/VL.1994.363618
Representing Nodes and Arcs in 3D Networks 
Glenn Franck and Colin Ware 
Faculty of Computer Science, University of New Brunswick, P.O. Box 4400 
Fredericton, N.B. E3B 5A3, e-mail: glenn@UNB.ca 
Abstract 
This paper introduces six graphical principles for  3 0  
network displays. These are justified with examples from 
GraphVisualizer3D, a system developed by the authors to 
investigate the problems of 3 0  visualization of 
information networks. GraphVisualizer3D enables the 
exploration of sulface color, surface texture, object shape, 
arc shape and labeling conventions. 
1. Introduction 
The creators of Cone Trees claim that approximately one 
thousand nodes are representable using a 3D tree structure 
[2], considerably more than could be understood in 2D. 
Our recent experiments involving a 3D graph tracing task 
showed that test subjects were able to comprehend about 
three times as much information in an interactive, 3D 
environment as in a comparable 2D one, if both stereo 
viewing and motion parallax information is available [6 ] .  
When constructing a 3D diagram, the design space is 
enlarged considerably. Such factors as 3D form, lighting 
models and viewing angles become critical. This paper 
describes a set of design rules that we have developed to 
help create good representations of arbitrary networks of 
information in 3D space, and presents some examples we 
have implemented in a prototype system called 
GraphVisualizer3D (GV3D). The kind of graph we are 
interested in is one for which each node can contain an 
entire sub graph, and each arc can represent a bundle of 
arcs. This is sometimes called a compound digraph 
[4].Our primary test case is the visualization of software 
code, and, in particular, object-oriented C++ code for 
which there seems to be a natural mapping from software 
objects to corresponding visual objects. 
2. Semiotic Principles 
As a result of our research with the GV3D system, we 
have found the following six semiotic principles to be 
helpful in system design for 3D network representation. 
Principle 1: entities should become graphical 
objects 
Especially in 3D, a visual object takes on a concrete 
immediate quality that makes it both easy to remember 
and easy to recognize and place in the context of other 
objects [ 5 ] .  Figure 1 illustrates some of the node 
representations we have developed. We chose simple boxes 
or cubes because we use a rectangular grid as a layout aid 
and because they are well suited to nesting. Families of 
boxes represent state information (see also principles 3, 5 
and 6 ) .  When a box is open it enlarges and reveals its 
contents. Figure 1 shows four open states: transparent, 
wire frame, a box with only the faces furthest from the 
viewer drawn (backfaces) combined with wire frame and 
one that combines wire frame with transparency. The 
advantage of the backface methods is that information 
behind the node of interest is hidden. 
Figure 1. Different representation types for 
opened nodes. 
Principle 2: uses or communication relations 
should be represented by connecting spars 
Relations between the objects are naturally represented by 
connecting lines or arrows in a graphical representation. 
When these relationships are portrayed in 3D the lines 
become solid spars that run between two nodes. We have 
implemented six different arc representation, consisting of 
both solid spars and lines. We have tried a number of 
graphical devices to indicate the direction of a directed arc 
and some of these are illustrated in Figure 1. The 
simplest direction indicator is a color change along the 
length of the arc and this can give a reliable sense of 
direction [ 11. Other, more complex representations include 
eight sided pyramids and 3D arrows placed in a connecting 
line. We have found these to be useful in different 
circumstances; for example, for inheritance relations we 
use the fat pyramidal arc while for uses relations we use 
the arrow. 
189 
0-8186-6660-9194 $04.00 0 1994 IEEE 
Principle 3: attribute relations should be Principle 5: preservation of object constancy 
represented by surface and shape properties 
Color and texture are both excellent in distinguishing 
between different node types because in nature they 
distinguish between related classes of objects. Shape is 
also appropriate (see Figure 2). 
Objects must maintain their identity despite scale changes, 
viewing from different angles and distance and state 
changes. The following graphical devices help. 
Symmetry about a vertical axis helps make an object 
Animated state changes preserve identity. 
Rotating labels so that the textual labels always face 
recognizable from different directions. 
directly on to the user. ( illustrated in Figure 2.) 
ating 
ce 
Figure 2. A portion of a network showing 
nodes of various sizes in both open and 
closed states, with two labeling methods. 
Principle 4: attribute representations should 
be orthogonal 
As far as possible, we must design orthogonal families of 
attribute representations. An example of a non-orthogonal 
set would be a box that could be rendered either filled or in 
wire frame. Clearly in wire frame mode the color 
appearance will not as easily be seen. The theory of 
integral versus separable display dimensions applies here 
[3]. In general it would be better to use separable display 
dimensions such as orientation and color because these can 
be perceived independently. In order to facilitate different 
yet recognizably similar objects we generate families of 
graphical dimensions. 
Families by form 
By varying the shapes and sizes of objects, we can convey 
the impression of different types and amounts of 
information. The state of a box must be represented by 
changes in form that preserve identity. 
Families by color and transparency 
Color has three dimensions and we may choose to render 
different objects of the same family with, for example, the 
same hue (for identity) but different saturations (for state). 
Hue may be very good for labeling attributes in this way 
because hue changes are perceptually associated with the 
properties of the materials out of which an object is made. 
In a rendered 3D environment it is important that the 
surface color be orthogonal to the effects of shading. This 
makes surface lightness a poor choice for displaying 
attributes. Transparency allows the preservation of identity 
while showing open and closed states. 
Families by texture 
Visual textures can be arranged in order by orientation or 
size [7]. A problem with texture is that the appearance of 
most textures changes with scale, unless it is fractal in 
nature. 
Principle 6: recursive implementation of 
design rules 
If nesting is to be defined recursively, then the 
representation scheme must be graphically recursive. In 
GV3D, we instantiate this principle by allowing each node 
to contain an entire graph, wherein each node of that graph 
can contain an entire graph, and so on. In Figure 1, for 
example, the entire high-level graph of eight nodes and 
arcs is repeated inside each open node. 
3. Conclusions 
We feel that representing networks of nodes and arcs in 3D 
has clear benefits in that it enlarges the perceptual space 
available for information display. However, the costs of a 
transition to 3D data representations are considerable. A 
new set of diagrammatic conventions must be developed 
that map information structures to three dimensional 
objects in the display space; this is the problem of 3D 
semiotics and is the issue we have begun to address here. 
Acknowledgments 
We are indebted to Bruce Simpson of the University of 
Waterloo for the idea to use spars to represent arcs. 
NSERC provided funding. Arthur Ryman of IBM 
Toronto Labs and Tim Dudley of Bell Northern Research 
provided support and encouragement. 
References 
1. Fowler, D. and Ware, C. Strokes for Representing 
Univariate Vector Field Maps, Graphics Interface 
Proceedings (1989), pp. 249-253. 
2. Robertson, G.G., Mackinlay, J.D and Card, S. K., Cone 
Trees: Animated 3D Visualizations of Hierarchical 
Information. CH1'91 Proceedings. (1991) pp.189-194. 
3. Smith, L,. and Evans, P. Similarity, Identity and 
Dimensions: Perceptual Classification in Children and 
Adults, in Object Perception: Structure and Process, Shepp 
and Ballesteros, Eds, Lawrence Erlbaum 1989, 325-357. 
4. Sugiyama, K., and Misue, K., Visualization of Structural 
Information: Automatic Drawing of Compound Digraphs, 
IEEE Transactions on Systems, Man and Cybernetics, Vol. 
5 .  Ware, C., The Foundations of Experimental Semiotics, 
Journal of Visual Languages and Computing, 4 (1993), pp. 
6. Ware, C. and Franck, G., Visualizing Information Nets in 
Three Dimensions, University of New Brunswick technical 
report TR94-082, February, 1994. 
7. Ware, C. and Knight, W., Using Visual Texture for Infor- 
mation Display, ACM Transactions on Graphics (in press). 
21, NO. 4, JulylAugust 1991, pp. 876-892. 
9 1 - 100. 
190 


Representing Nodes and Arcs in 3D Networks

UNH Scholars' Repository

University of New HampshireUniversity of New Hampshire Scholars' RepositoryCenter for Coastal and Ocean Mapping Center for Coastal and Ocean Mapping10-1994Representing Nodes and Arcs in 3D NetworksGlenn FranckUniversity of New BrunswickColin WareUniversity of New Hampshire, Durham, colin.ware@unh.eduFollow this and additional works at: https://scholars.unh.edu/ccomPart of the Computer Sciences Commons, and the Oceanography and Atmospheric Sciences andMeteorology CommonsThis Conference Proceeding is brought to you for free and open access by the Center for Coastal and Ocean Mapping at University of New HampshireScholars' Repository. It has been accepted for inclusion in Center for Coastal and Ocean Mapping by an authorized administrator of University of NewHampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu.Recommended CitationFranck, G.; Ware, C., "Representing nodes and arcs in 3D networks," in Visual Languages, 1994. Proceedings., IEEE Symposium on ,vol., no., pp.189-190, 4-7 Oct 1994 doi: 10.1109/VL.1994.363618Representing Nodes and Arcs in 3D Networks Glenn Franck and Colin Ware Faculty of Computer Science, University of New Brunswick, P.O. Box 4400 Fredericton, N.B. E3B 5A3, e-mail: glenn@UNB.ca Abstract This paper introduces six graphical principles for  3 0  network displays. These are justified with examples from GraphVisualizer3D, a system developed by the authors to investigate the problems of 3 0  visualization of information networks. GraphVisualizer3D enables the exploration of sulface color, surface texture, object shape, arc shape and labeling conventions. 1. Introduction The creators of Cone Trees claim that approximately one thousand nodes are representable using a 3D tree structure [2], considerably more than could be understood in 2D. Our recent experiments involving a 3D graph tracing task showed that test subjects were able to comprehend about three times as much information in an interactive, 3D environment as in a comparable 2D one, if both stereo viewing and motion parallax information is available [6 ] .  When constructing a 3D diagram, the design space is enlarged considerably. Such factors as 3D form, lighting models and viewing angles become critical. This paper describes a set of design rules that we have developed to help create good representations of arbitrary networks of information in 3D space, and presents some examples we have implemented in a prototype system called GraphVisualizer3D (GV3D). The kind of graph we are interested in is one for which each node can contain an entire sub graph, and each arc can represent a bundle of arcs. This is sometimes called a compound digraph [4].Our primary test case is the visualization of software code, and, in particular, object-oriented C++ code for which there seems to be a natural mapping from software objects to corresponding visual objects. 2. Semiotic Principles As a result of our research with the GV3D system, we have found the following six semiotic principles to be helpful in system design for 3D network representation. Principle 1: entities should become graphical objects Especially in 3D, a visual object takes on a concrete immediate quality that makes it both easy to remember and easy to recognize and place in the context of other objects [ 5 ] .  Figure 1 illustrates some of the node representations we have developed. We chose simple boxes or cubes because we use a rectangular grid as a layout aid and because they are well suited to nesting. Families of boxes represent state information (see also principles 3, 5 and 6 ) .  When a box is open it enlarges and reveals its contents. Figure 1 shows four open states: transparent, wire frame, a box with only the faces furthest from the viewer drawn (backfaces) combined with wire frame and one that combines wire frame with transparency. The advantage of the backface methods is that information behind the node of interest is hidden. Figure 1. Different representation types for opened nodes. Principle 2: uses or communication relations should be represented by connecting spars Relations between the objects are naturally represented by connecting lines or arrows in a graphical representation. When these relationships are portrayed in 3D the lines become solid spars that run between two nodes. We have implemented six different arc representation, consisting of both solid spars and lines. We have tried a number of graphical devices to indicate the direction of a directed arc and some of these are illustrated in Figure 1. The simplest direction indicator is a color change along the length of the arc and this can give a reliable sense of direction [ 11. Other, more complex representations include eight sided pyramids and 3D arrows placed in a connecting line. We have found these to be useful in different circumstances; for example, for inheritance relations we use the fat pyramidal arc while for uses relations we use the arrow. 189 0-8186-6660-9194 $04.00 0 1994 IEEE Principle 3: attribute relations should be Principle 5: preservation of object constancy represented by surface and shape properties Color and texture are both excellent in distinguishing between different node types because in nature they distinguish between related classes of objects. Shape is also appropriate (see Figure 2). Objects must maintain their identity despite scale changes, viewing from different angles and distance and state changes. The following graphical devices help. Symmetry about a vertical axis helps make an object Animated state changes preserve identity. Rotating labels so that the textual labels always face recognizable from different directions. directly on to the user. ( illustrated in Figure 2.) ating ce Figure 2. A portion of a network showing nodes of various sizes in both open and closed states, with two labeling methods. Principle 4: attribute representations should be orthogonal As far as possible, we must design orthogonal families of attribute representations. An example of a non-orthogonal set would be a box that could be rendered either filled or in wire frame. Clearly in wire frame mode the color appearance will not as easily be seen. The theory of integral versus separable display dimensions applies here [3]. In general it would be better to use separable display dimensions such as orientation and color because these can be perceived independently. In order to facilitate different yet recognizably similar objects we generate families of graphical dimensions. Families by form By varying the shapes and sizes of objects, we can convey the impression of different types and amounts of information. The state of a box must be represented by changes in form that preserve identity. Families by color and transparency Color has three dimensions and we may choose to render different objects of the same family with, for example, the same hue (for identity) but different saturations (for state). Hue may be very good for labeling attributes in this way because hue changes are perceptually associated with the properties of the materials out of which an object is made. In a rendered 3D environment it is important that the surface color be orthogonal to the effects of shading. This makes surface lightness a poor choice for displaying attributes. Transparency allows the preservation of identity while showing open and closed states. Families by texture Visual textures can be arranged in order by orientation or size [7]. A problem with texture is that the appearance of most textures changes with scale, unless it is fractal in nature. Principle 6: recursive implementation of design rules If nesting is to be defined recursively, then the representation scheme must be graphically recursive. In GV3D, we instantiate this principle by allowing each node to contain an entire graph, wherein each node of that graph can contain an entire graph, and so on. In Figure 1, for example, the entire high-level graph of eight nodes and arcs is repeated inside each open node. 3. Conclusions We feel that representing networks of nodes and arcs in 3D has clear benefits in that it enlarges the perceptual space available for information display. However, the costs of a transition to 3D data representations are considerable. A new set of diagrammatic conventions must be developed that map information structures to three dimensional objects in the display space; this is the problem of 3D semiotics and is the issue we have begun to address here. Acknowledgments We are indebted to Bruce Simpson of the University of Waterloo for the idea to use spars to represent arcs. NSERC provided funding. Arthur Ryman of IBM Toronto Labs and Tim Dudley of Bell Northern Research provided support and encouragement. References 1. Fowler, D. and Ware, C. Strokes for Representing Univariate Vector Field Maps, Graphics Interface Proceedings (1989), pp. 249-253. 2. Robertson, G.G., Mackinlay, J.D and Card, S. K., Cone Trees: Animated 3D Visualizations of Hierarchical Information. CH1'91 Proceedings. (1991) pp.189-194. 3. Smith, L,. and Evans, P. Similarity, Identity and Dimensions: Perceptual Classification in Children and Adults, in Object Perception: Structure and Process, Shepp and Ballesteros, Eds, Lawrence Erlbaum 1989, 325-357. 4. Sugiyama, K., and Misue, K., Visualization of Structural Information: Automatic Drawing of Compound Digraphs, IEEE Transactions on Systems, Man and Cybernetics, Vol. 5 .  Ware, C., The Foundations of Experimental Semiotics, Journal of Visual Languages and Computing, 4 (1993), pp. 6. Ware, C. and Franck, G., Visualizing Information Nets in Three Dimensions, University of New Brunswick technical report TR94-082, February, 1994. 7. Ware, C. and Knight, W., Using Visual Texture for Infor- mation Display, ACM Transactions on Graphics (in press). 21, NO. 4, JulylAugust 1991, pp. 876-892. 9 1 - 100. 190 

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