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Interactive Rendering and Stylization of Transportation
Networks using Distance Fields
Matthias Trapp, Amir Semmo, Jürgen Döllner
Hasso Plattner Institute, University of Potsdam, Germany
INTRODUCTION
Paris Street Map –1780
P1: contour lines surround fine-textured fills or solid colors
to add visual contrast and improve figure-ground perception
P2: primary streets overlap secondary or tertiary streets in
hierarchical representations of street networks; wavy or fuzzy
to express uncertainty
P3: names follow principal line directions and are placed within
streets or outside line segments
London Street Map –1913
London Underground Map –1933
Modern Tourist Map of Paris
P7: yellow established as a conventional color tone for main
streets, with a discrete gradation towards grey and white
shading for tertiary roads
P6: streets are tinted using qualitative color schemes to represent
street classes and distinguish them from the underlying terrain
P5: a hierarchy of emphasis is drawn among reference elements,
such as different line weights and colors to portray different
grades of roads
P4: dynamic filtering and scaling of geometric features improves
perception of roads at high view distances and avoids
cluttering.
Conceptual and Technical Requirements
▪Pre-processing of discrete level-of-details consume additional memory and yield
incoherent rendering when switching between these levels during zooming or within
perspective projection.
→Levels-of-Detail should be computed during rendering based on viewing settings
▪Increasingly detailed networks require high amounts of main/video memory.
→Network representation should exhibit a small memory footprint and fast updates
▪View-dependent cartographic stylization of transportation networks are key features for a
number of applications.
→Rendering technique should provide a sufficient parameterization, i.e., covering level-of-detail
rendering, interactive filtering, and highlighting
RELATED WORK
Related Work :: Overview
Street Rendering Approaches
Object-space Approaches
Geometry-based Approach
Texture-based Approach
Screen-Space Approaches
Stencil-based Approach
Discard-based Approach
Geometry-based Approach
Basic Principle:
▪Pre-compute geometry at different LoD
▪Forward rendering geometry
▪Most flexible approach w.r.t. stylization
Limitations:
▪High memory consumptions for complex networks
▪No transitions between static LoD
▪High rendering costs
Texture-based Approach
„Interactive 3D Visualization of Vector Data in GIS”
O. Kersting, J. Döllner, ACM GIS 2002
Basic Principle:
▪Generate texture trees from geometry
▪Off-screen rendering at different resolutions
▪Use for texturing during scene rendering
Limitations:
▪Relies on data pre-processing
▪Requires intermediate representation
▪Suffers from texturing artifacts
Stencil-based Approach
„High-Quality Cartographic Roads on High-Resolution DEMs”
M. Vaaraniemi, M. Treib, R. Westermann, WSCG Journal 2011
Basic Principle:
▪Generate shadow volume per street segment
▪Avoid cracks between segments using cap cones
▪Enables distance-based scaling of street segments
▪Rendering using shadow volume approach
Limitations:
▪Requires additional data structure (volumes)
▪Limited styling capabilities (color + outline)
Discard-based Approach
„A screen-space approach to rendering polylines on terrain”
D. Ohlarik, P. Cozzi; SIGGRAPH Poster 2011
Basic Principle:
▪Extrude polylines to walls
▪Compute intersection with terrain
▪Discard fragments accordingly
▪Avoid dashing and smearing
Limitations:
▪Stylization with single color only
▪No distance-dependent segment width
Distance-fields for Stylization Parametrization
„ Real-Time Rendering of Water Surfaces with Cartography-Oriented Design”
A. Semmo, J. E. Kyprianidis, M. Trapp, J. Döllner; CAe 2014
APPROACH
Overview of Approach
Forward Rendering Pass Deferred Rendering Pass
Overview of Distance-Field Generation
Geometry Generation
Attributed Vertex Cloud
+
Geometry Shader
+
Vertex Pulling
Encoding of Distance using Texturing
dresult = min(dsource , ddestination)
Blending Modes
No Blending Min-Blending
Distance Field Colored Distance Field Colored
Result: 2D Texture-Array
Memory consumptions: #layer
width
height
precision (3 * 32 Bit = 12 Byte)
Evaluation of Distance Fields :: Procedural Textures
Procedural textures evaluated on a per-fragment basis:
▪Deferred texturing based on distance fields
▪Application of procedural and image textures possible
▪Bottom-up compositing based on street rank
“Improved Alpha-Tested Magnification
for Vector Textures and Special Effects”
Chris Green; SIGGRAPH 2007
Final Compositing Step
Bottom-up evaluation of each layer (street category) and blending
RESULTS & DISCUSSION
Application Examples :: Distance-based Evaluation
Application Examples :: Stylization Variants
Application Examples :: Regions-of-Interest
Application Examples :: Regions-of-Interest
Performance Evaluation
▪Test data sets of different complexity
from Open Street Map (OSM) data base
▪Approach is fill-limited w.r.t. number of
street categories to render
ID
Data Set
# Nodes
#
Ways
A
Berlin 1
5571
1028
B
Istanbul
2004
263
C
Berlin 2
9502
1766
A B C A B C A B C
390 x 260 670 x 450 1280 x 800
1 Category 3 2,9 3 3 2,9 3 25,5 25,4 25,3
2 Categories 3,2 3,3 3,4 3,2 3,3 3,4 29 29 29,2
4 Categories 4,1 4,1 4,2 4,1 4,2 4,2 36,1 26,2 36,2
8 Categories 5,5 5,4 5,5 5,7 5,6 5,8 50,1 50,1 50,2
0
10
20
30
40
50
60
Milliseconds
Limitations
Distance-field generation:
▪Intrusion
▪Protrusion
Memory consumptions for large numbers of categories
Intrusion
Protrusion
Future Work :: Geometry Draping
Draping
Digital Elevation Model Result
Planar Network Geometry
Future Work :: Geometries
▪Generate alternative geometric representations
▪View-dependent adaptation of geometric representations
Conclusions
▪A concept for high-quality cartographic rendering exemplified
for complex street networks.
▪Interactive hardware-accelerated rendering technique having
minimal memory footprint for network representation.
▪Interactive stylization and colorization using deferred texturing
based on distance fields generated on per-frame basis
▪Potentials for future research