ABSTRACT
This paper describes several experiments in visualizing
implications of landscape planning and design decisions using
a combination of GIS, CAD and video animation technology. We
use simple grid-cell GIS databases and site-scale polygonal models
to provide visualizations of site planning design proposals and
environmental impacts, with both static and animated images.
Rather than pursuing 'photo-realistic' simulations, we are interested
in how abstractions and representational conventions can be used
to gauge visual and environmental impacts of proposals for landscape
change, in a dynamic, interactive computer-aided design environment.
Stephen M. Ervin
Department of Landscape Architecture
Harvard University Graduate School of Design
48 Quincy St. Cambridge, Massachusetts, USA 02138
email: servin[@]gsd.harvard.edu
VISUALIZING N- DIMENSIONAL IMPLICATIONS of
TWO-DIMENSIONAL DESIGN DECISIONS
Introduction
This paper describes several experiments in visualizing
implications of landscape planning and design decisions, using
a combination of GIS, CAD and video animation technology in a
heterogeneous computer network environment. Proposals for landscape
change -- such as those related to new housing and infrastructure
development, wate management or energy facilities, transportation
corridors, forestry management and reforestation, etc. -- are
initially represented and analyzed as two-dimensional grid-cell
plans, using traditional raster GIS techniques. First-order evaluations
of environmental impacts of proposed changes, evaluated by models
of varying degrees of complexity, can be represented as color-coded
maps: red for danger, black for disaster, yellow for warning
and green for acceptable, for example. In addition, the gross
physical implications -- new masses of buildings, bodies of
water, areas of pavement, clearings or new masses of vegetation,
e.g. -- can be represented as simple polygonal models, scaled
and shaped appropriately. These three representations: original
plans, impact maps and three-d models -- provide data for a variety
of modes of visualization. The three dimensional polygonal models
can be 'walked thru', using standard three-d modelling techniques,
and viewed thru 'color-coded glasses', seeing the landscape not
in 'natural' color, but in meaningful color, hece, with an
added dimension. When these images are integrated or viewed over
time, using simple animation techniques, we are up to five dimensions,
and counting...
The close integration of GIS , CAD, video and other
visualization systems is still in its infancy (cf Arc-CAD and
other similar systems) , and both theoretical and mechanical problems
remain in the way of satisfactory integration. This paper reports
on one small effort to bridge the gap, and to bring the benefits
of n-dimensional visualization together with the power of geographic
analysis: a graduate landscape design studio concerned with
siting and designing a new community, using a combination of raster
GIS software (macGIS from the University of Oregon) and interactive
polygonal surface software (the CLRView/ECOView system from the
University of Toronto Center for Landscape Research) in a heterogeneous
network of computer workstations.
Geographic and Environmental Analysis
We use simple grid-cell GIS databases and site-scale
polygonal models to provide visualizations of design proposals
and environmental impacts with both static and animated images.
In our second-year graduate landscape design curriculum, we
teach two courses that introduce GIS approaches, and cartographic
modelling, using simple Macintosh software (macGIS [Hulse 1987]),
for site selection and evaluation. Students are given a database
in the form of eight layers, or 'coverages', for two sites, on
two disks in raster GIS format. Working with these base data,
and following the framework of models described by [Steinitz
90] , the students develop a series of analytical 'process', 'attractiveness'
, 'vulnerability ', and 'impact' models which guide their site
selection and site plan evaluation process. Traditional cartographic
analyses [Burrough 1982, Tomlin 1990] yield site evaluations,
sensitivity analyses and attractiveness and vulnerability models,
based on a variety of criteria, from landscape ecological concerns
to cost and visual preference. Typically there are 8 - 12 models
which go into this evaluation -- "Soil Erosion Potential",
"Groundwater Quality", "Cost of Construction",
"MicroClimate and Energy Impacts" are examples of such
models. This approach has proven useful for both teaching the
logic of geographic analysis and introducing the complexity of
large scale land use decisions [Ervin 1991]. Since 1990 we have
been exploring the explicit addition of visual analysis to this
repertoire of models, as described below.
Based on some number of analytical models (but often
in an 'intuitive' or 'personal' fashion), a preliminary site plan
is developed by each student or team in the raster GIS system,
where each (approximately one acre) cell is assigned a new land
use code -- a simp[le two-digit integr code, modelled after the
USGS land use categories (but including more varieties of residential
land uses, and possibly supplemented by special-purpose land uses
developed within the context of the studio).
These preliminary land use plans are developed based
on an initial analysis of the site using the analytical models
mentioned above; the plans are then subjected to analysis by
running them through more models which evaluate the impacts of
the proposed development pattern. The plans are evaluated for
gross impact using environmental impact models, which yield impact
maps in the form of coded raster maps indicating impacts in five
categories: 0= Not Applicable, 1=Compatible, 2=Minor Impact,
3=Major Impact, 4=Disaster, or 'Threshold' Impact. Then one (perhaps
overly) simple quantitative analysis of any proposed site plan
is the linear sum of the impacts over the proposed site plan area
-- the lower the better. We stress the point that negative impacts
are not necessarily 'Stop' signs, but are rather 'Warning' signs,
which raise flags in areas of concern, and remind the designer
to make special efforts to mitigate negative effects. Figure
1 shows two impact maps from one such sequence.
Figure 1. Typical Vulnerability Assessment maps
These vulnerability and impact assessments are informative
and useful, but at a rather coarse level of aggregation. Furthermore,
designers (and design students) are often frustrated at this
stage by not having an 'image' of their proposed plan except in
the most diagrammatic form. In addition, the possibility of
studying motion through, around and of the site is important for
many of these plans, as they are typically concerned with issues
of public/private access and view. A standard visibility analysis
in a GIS can (approximately) answer the question "Can you
see the dump from the road?", but not "What might it
look like?" -- much less "What will it look like".
Visualization
The simplest type of visualization is the GIS technique
off 'draping', superimposing a pattern on a three-dimensional
terrain. Figure 2 shows a typical site plan, 'draped' over
terrain with roads and major streams superimposed, on a 3600 acre
site.
Figure 2. Site plan draped over terrain
In order to get at the question of "What might
it look like?", at this preliminary stage, we have developed
a set of symbols for three-dimensional representation: buildings
and houses of varying densities and overall form, several types
of vegetation, smokestacks and parking lots, for example. These
symbols, corresponding to the land use codes, can be arrayed
in three-dimensions, over a digital terrain model, to provide
a preliminary 3-d analysis of the (possible) form of the proposed
site plans. These views are understood to be approximations;
more realistic than just plan views, but more diagrammatic than
final renderings or presentation drawings. Figure 3. shows a
sampling of some of these simple polygonal figures.
Figure 3. Land Use 'Objects'
Working directly from the GIS raster files of the
proposed plan, a translation program is used to generate 3-D
polygonal surface files using a library of symbols to schematically
illustrate a landscape of land uses with these simple objects
(trees, houses, etc). One version (developed by the author) can
be used directly on the Macintosh (albeit slowly) for preliminary
static views.
Figure 4 shows a composite perspective view of the
center of one of the study sites, [produced on a Macintosh with
software written by the author]. In this view, the ELEVATION
data has been rendered as a triangulated underlay , colored by
a map that combines land cover and hydrology. On top of this
terrain, vegetation is represented by simple two-dimensional symbols
produced with a slight random variation in size and shape; buildings,
residential and municipal, by three-dimensional block figures.
This version is a black and white approximation of the colored
original, in which colors are chosen for a more 'realistic' approximation
to natural phenomena (i.e.. blues, greens, browns).
Figure 4. Perspective view of Study Area
In addition, once these sites are projected into
three-dimensional surface- or solid- models, it is possible to
use other CAD and image processing software to enhance the three-dimensional
understanding of the proposal; for example, by providing animated
walks-through or fly-overs of the site. We use the POLYTRIMS
and CLRView/ECOView visualization and animation software for
the Personal IRIS, developed by the Centre for Landscape Research
at the University of Toronto. Using this hardware/software combination,
it is possible to generate real-time animations of complex scenes
represented as three-dimensional planar surfaces.
Once the proposed site plans have have been generated
on the macintosh, and and converted onto the IRIS, our planning
and design students can fly, drive or walk through or around their
plans, to evaluate the overall form and visual impact of the
proposal. The images produced are rough in many ways: all trees
and buildings are alike and rather diagrammatic; colors are shaded
but there is no provision for the subtleties of texture or curved
surfaces; the ground is broken up into half-acre colored triangles,
to name but a few of the visual objections -- but nonetheless
these simulations are remarkably informative and useful! Figure
5. shows one image from an IRIS simulation.
Figure 5. IRIS view
Using these simulations, judgments can be made at
the preliminary design stage about dimensions and densities of
view corridors, buffers, height limitations, vantage points and
special views. In our present studio schedule, this preliminary
review occurs at mid-semester, so students have the opportunity
for two or more cycles of revision and re-evaluation using this
technology before final plans are developed. Right now there
are logistical complications that make the process more time-consuming
and less transparent than we would like, but these are circumstances
that will continue to change. While we don't presently get designers
working directly on the IRIS (as Professor John Danahy does in
his studios at Toronto [Danahy 1990]), we do anticipate a seamless
and transparent integration of this visualization tool into the
preliminary design process that will continue to rely on GIS.
In this sense, the visual evaluation becomes just one more in
a suite of evaluation models used to inform the design and planning
process.
One use of this set of techniques is to begin to
appreciate chane over time, using color cues along with animation.
Figure 6 shows four frames of views of the same terrain as in
fugure 4, but set in the four seasons: summer, fall, winter,
spring. In each case, the underlying data model has not changed,
only the viewing parametrs have. That is, different symbols
have been substtituted as appropariate ( bare branchde deciduous
trees in the winter, e.g.) and color palettes have been changed
(fields, for example, are white in winter, bright green in
spring, medium green in summer, and tan in the fall.) These
visualizations are the most 'life-like' in their intent, as they
give a feeling of different aspects fo the landscape at different
times of year. Other dimensions of the landscape -- such as visibility
distances, or sun/shade pockets, 'sense of enclosure' or 'view
of water', also change with thseasons, and these analyses can
be ovberlaid on the substrate of the colored landscape to add
to the visualization of the landscape character in many of its
dimensions.
We have carried this integration of visualization and analysis one step further, providing a way of viewing proposed changes in the context of their impacts. We simply use the color code for impacts -- red for Bad, green for Good, yellow for Neutral -- to tint the three-dimensional landscape. Thus trees in compatible zones are green, whereas trees in negatively impacted areas appear in red; likewise for other features, such as water bodies and structures. This approach -- wearing virtual 'rose-colored glasses' -- is simple but effective. Patterns of impacts that have an element of geographic or spatial correlation (such as along drainage courses, or ridgetops, for example) are glaringly obvious in this approach, and seem much more immediate when seen in pseudo-three-dimensions than when simply presented as a colored impact map.
Similarly, we can animate motion through these false-colored
landscapes, using the speed and graphic power of the IRIS computers,
and the interface developed for the CLRView program. Walking
from the green forest into the red housing and parking area,
or taking a drive along a road and watching the hilltops along
the road to see if the highly impacted landscape is visible in
red, are both more personal and engaging than simply seeing a
viewshed analysis. It is this engagement that gives the power
to this form of visualization.
Conclusions
Rather than pursuing 'photo-realistic' simulations,
we are interested in how abstractions and representational conventions
can be used to gauge visual and environmental impacts in a dynamic,
interactive computer-aided design environment.
Computer programs for manipulating geographic information
(GIS) provide powerful tools for addressing landscape design and
planning problems, but typically handle data that are too coarse
for three dimensional site-scale design. Regional landscape planning
and urban design require higher levels of abstraction, and larger
scope (smaller scale) decisions, than do site-scale project designs,
which are best supported by CAD systems with their fine resolution
and capacity for detailed geometry, etc. Designers naturally
work back and forth between these scales, and, to some extent,
between these computer media.
The images produced are rough in many ways: all
trees and buildings are alike and rather diagrammatic; colors
are shaded but there is no provision for the subtleties of texture
or curved surfaces; the ground is broken up into colored triangles
-- but nonetheless these simulations are remarkably informative
and useful. This methodology linking planning scale analysis with
site-scale three-and four- dimensional simulations offers promise
for GIS-CADD integration, and animation.
We stress that the visualizations so produced are
attempts to answer the question "What might
it look like, rather than "What will it look like?
So we are not quite treading the murky waters of 'photo-realistic'
visual simulation, with its technical complications (ray-tracing,
surface texture mapping, shadow casting and all...), and its
deep-seated theoretical problems (who says what constitutes realism,
anyway?). Instead, we are producing the equivalent of a designer's
quick thumbnail sketch, cross-section or doodle. This has undeniable
value in the design process, but no overly great weight is placed
upon it - - these images are ephemeral and mutable at will --
designed for change and recycling, rather than as finished renderings.
(This is not to say that the three-dimensional substrate so created
could not be used as the basis for more finished renderings --
only that we do not at present use them that way.) Questions about
design process -- "When are what graphic products produced,
and for whom?", for example -- are raised, but not answered,
by our efforts.
Whereas the environmental sensitivity and impact
models are defensible (Steinitz, 1979), by virtue of being reproducible
and articulate (although this does not imply that they are necessarily
correct), individual responses to visual images are neither so
reproducible nor so articulate. We believe that these kinds of
visualizations are important component of any public debate about
land use plans and impacts, with the caveat that the public may
not be so ready to make the distinction between "might
look like" and "will look like". There
is a tendency for non-designers to take graphic products literally,
rather than suggestively; this is a major disadvantage of this
technique outside of designers' private investigations. For
designers, who are more sophisticated (and hence critical, in
the best sense) about graphic products and design processes,
we are adding one more element into a rich and complex soup of
models and abstractions (Van Der Schans, 1990) about the world
being designed and explored. This idea, of multiple views of
evolving models, is the best underpinning for comprehensive computer-aided
design, whether it's called CAD or GIS (or anything else...)
We imagine (and are undertaking) a number of improvements
and refinements to the present system. They range from faster
IRISes that can support real-time integration of two-dimensional
raster layout, impact analysis and visualization along with three-dimensional
renderings -- thereby eliminating the intermediate translation
step -- to constraint-based models that enable 'working backwards',
designing directly in three-dimensions and producing impact analyses
directly. Interface questions, not surprisingly, begin to be
significant when interactive design processes are envisioned,
and questions of screen layout, response time, visual cues,
et al. all become more than just academic. We have several on-going
investigations looking at interface aspects of the system, and
expect slow convergence on a flexible, workable, multi-windowed
and multi-abstraction--level environment for exploring land use
plans and environmental impacts.
References
Burrough,Peter. 1982. Principles of Geographic Information Systems for Land Resources Assessment. Clarendon, Oxford.
Danahy, John 1990. "Irises in a Landscape: An Experiment in Dynamic Interaction and Teaching Design Studio", in McCullough, Mitchell & Purcell (Eds) The Electronic Design Studio, Cambridge, MA: MIT Press
Ervin, Stephen M. 1991 "Teaching Theories and Methods of LandscapePlanning with low-cost GIS", in CELA Selected Papers, Vol. 3.
Hulse, David & Kit Larsen. 1989. macGIS A Geographic Information System for the Macintosh; The User's Guide. University of Oregon.
Munroe, Bob, 1988 "Video and Computer Animated Graphics in Engineering Visualization", Proceedings of 1988 National Computer Graphics Conference, Fairfax, VA: NCGA
Steinitz, Carl. 1990. "A Framework for Theory " Landscape Journal, Fall 1990.
Steinitz, Carl. 1979. Defensible Processes for Regional Landscape Design. L.A.T.I.S. American Society of Landscape Architects, Washington, D.C.
Tomlin, C. Dana. 1990. Geographic Information Systems and Cartographic Modelling, Prentice-Hall.
Van Der Schans, Rene. 1990. "The WDGM Model, a formal Systems View on GIS", International Journal of Geographical Information Systems,, v.4.no.3 225-239
Goldman, Glenn and M.S.Zdepski , 1989. "Previsualization
for Architectural Design", Proceedings of 1989 National Computer
Graphics Conference, Fairfax, VA: NCGA
BIOGRAPHICAL NOTE
Stephen M. Ervin has a Master's Degree in Landscape
Architecture from the University of Massachusetts at Amherst,
and a PhD in Urban Studies from MIT. He is past chairman of
the American Society of Landscape Architects' Committee on Computers.
His teaching at the Harvard Graduate School of Design is in the
area of technology, both construction and computation. Research
interests are in computational approaches to landscape planning
and design, integration of CAD and GIS, and algorithmic processes
in the landscape.