Post on 16-Dec-2015
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Non-Photorealistic Rendering
FORMS
Mesh (~170)Mesh (~170) Parametric (~16)Parametric (~16)
Implicit/CSG (~9)Implicit/CSG (~9)
Volumetric (~28)Volumetric (~28)
3D Object Representation in NPR3D Object Representation in NPR
Point Cloud (~4)Point Cloud (~4)
Fundamental GoalsFundamental GoalsTraditional IllustrationTraditional Illustration
Create convincing impressions of 3D Create convincing impressions of 3D forms on paperforms on paper
Depict solid masses in spaceDepict solid masses in space
Show their various structural conditionsShow their various structural conditions
Suggest their different surface Suggest their different surface characteristicscharacteristics
Communication Pipeline in Communication Pipeline in Science IllustrationScience IllustrationCommunication Pipeline in Communication Pipeline in Science IllustrationScience Illustration
SCIENTISTSCIENTIST ILLUSTRATORILLUSTRATOR
Provides materialProvides material Requests informationRequests information
descriptiondescription Records informationRecords information
specimenspecimen Studies specimenStudies specimen
Makes rough drawingMakes rough drawing
Makes detailed preliminary drawingMakes detailed preliminary drawing
Checks detailed preliminary drawingChecks detailed preliminary drawing
Corrects preliminary drawingCorrects preliminary drawing
Checks correctionsChecks corrections
Produces renderingProduces rendering
Checks renderingChecks rendering
Labels drawingLabels drawing
Checks labelingChecks labeling
Return specimenReturn specimen
CompositionPrinciples
Finished Rendering
Initial SketchRendering
Techniques
Line (Ink)Scratch Board PencilCoquille BoardWash,…
Subject
AnatomyBotanyZoologyPaleontologyArcheology Study
Selection
FormsLighting
Steps
Study the Subject!Study the Subject!Illustration terminologyIllustration terminology
Communicate subtleties and eliminate ambiguitiesCommunicate subtleties and eliminate ambiguities
Move the subject around, do not just concentrate Move the subject around, do not just concentrate on one parton one part
Observe the general appearance firstObserve the general appearance first
Identify the most significant features Identify the most significant features
Only include detail which is necessary in your Only include detail which is necessary in your drawingdrawing
Study the Subject!Study the Subject!Illustration terminologyIllustration terminology
Extract major features (folding regions, surfaces areas, volumes, curvatures)
Highlights to visually eliminate extraneous details and reduce the subject to simple lights and darks
Textures, angles where different forms join, perspective, foreshortening
Analyze the Object!Analyze the Object!NPR terminologyNPR terminology
Exactly same goals as in traditional illustration!
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary
Outline : Model Boundary
Only in non-closed models
Polygonal model :
at least one polygon has at at least one polygon has at least one edge that is not least one edge that is not shared with any other shared with any other polygonpolygon
The vertex is adjacent to a boundary edge
Outline : Model Boundary Cusps (Vertex)
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary Silhouette
Outline : View Silhouette
Silhouette point : point on the surface where V (u, v) . N (u, v) = 0 or the angle between V(u, v) and N(u, v) is 900
Outline : View Silhouette
N . V < 0 N . V > 0
N . V = 0
Polygon is perpendicular to the view direction
An edge between two polygons is a silhouette edge
if the edge is shared by a front-facing and a back-facing polygon
The vertex is adjacent exactly 2 silhouette edges, one front-facing and the other back-facing
Outline : View Silhouette Cusps (Vertex)
The vertex is adjacent to more than 2 silhouette edges
Outline : View Silhouette Cusps (Vertex)
The vertex is adjacent exactly 2 silhouette edges, one front-facing and the other back-facing
The vertex is adjacent to more than two silhouette edges
Outline : Cusps (Vertex)
The vertex is adjacent to a boundary edge
Terminology on SilhouettesTerminology on Silhouettes
Traditional IllustrationTraditional IllustrationNPRNPR
ProfileProfile(Computer Vision, Modeling)(Computer Vision, Modeling)
SilhouetteSilhouette
BoundaryBoundary
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary Silhouette
X
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary
Crease(+ otherdiscontinuities)
Silhouette
X
Polygonal model: an edge between two front-facing polygonswhose dihedral angle theta is above some threshold
NURBS surface: any region where the surface normal changes abruptly, i.e., C1 discontinuities
Interior : Model/Threshold Crease
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary
Crease(+ otherdiscontinuities)
Crease(+ otherdiscontinuities)
Silhouette
X
Interior : Model/Threshold Other Discontinuities
Sousa et al., Precise Ink Drawing of 3D Models,
Eurographics 2003
Pulla, Pulla, Curvature Based Segmentation of 3D MeshesCurvature Based Segmentation of 3D Meshes, , Prism/3DKPrism/3DK ASU, 2000
Interior : Model/Threshold Other Discontinuities
Alliez et al., Anisotropic Polygonal Remeshing,
SIGGRAPH 2003
Interior : Model/Threshold Other Discontinuities
Interior : Model/Threshold Other Discontinuities
Sousa and Prusinkiewicz, A Few Good Lines: Suggestive Drawing of 3D Models,
Eurographics 2003
Sousa et al., Depicting Shape Features with Directional Strokes and Spotlighting, Computer Graphics International 2004
Interior : Model/Threshold Other Discontinuities
Model dependent
Threshold dependent
View dependent
Outline form of the object
Interior form of the object
Boundary
Crease(+ otherdiscontinuities)
Crease(+ otherdiscontinuities)
Silhouette
X
X
1979 1979 Appel et al Appel et al The haloed line effect for hidden line eliminationThe haloed line effect for hidden line eliminationSIGGRAPHSIGGRAPH
19821982 RothRothRay Casting for Modeling SolidsRay Casting for Modeling SolidsComputer Graphics and Image ProcessingComputer Graphics and Image Processing
19871987 Wyvill et alWyvill et alSketches by Ray TracingSketches by Ray Tracing Computer Graphics InternationalComputer Graphics International
19871987 SasadaSasadaDrawing Natural Scenery by Computer GraphicsDrawing Natural Scenery by Computer Graphics Computer-Aided DesignComputer-Aided Design
19871987 Kamada, T. and Kawai, S.Kamada, T. and Kawai, S.An Enhanced Treatment of Hidden LinesAn Enhanced Treatment of Hidden LinesACM Transactions on GraphicsACM Transactions on Graphics
19881988 Veenstra and Ahuja Veenstra and Ahuja Line drawings of octree-represented objectsLine drawings of octree-represented objectsACM Transactions on GraphicsACM Transactions on Graphics
Line Drawing of 3D Models
1979 1979 Appel et al Appel et al The haloed line effect for hidden line eliminationThe haloed line effect for hidden line elimination
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19871987 Kamada, T. and Kawai, S.Kamada, T. and Kawai, S.An Enhanced Treatment of Hidden LinesAn Enhanced Treatment of Hidden Lines
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19881988 Veenstra and Ahuja Veenstra and Ahuja Line drawings of octree-represented objectsLine drawings of octree-represented objects
Line Drawing of 3D Models