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Terrain

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					    Terrain




Three recent works
Harold: A world made of drawings
(Cohen, Hughes, Zeleznik – NPAR 2000)

Aim:
   Create 3D worlds via a drawing paradigm


Approach:

Stroke projection (Draw on sky, draw on ground)





Billboards (rotate to face viewer)





Create terrain via ridge silhouette (height-field)

Harold: A world made of drawings
(Cohen, Hughes, Zeleznik)

Interface:

   Non photo-realistic

   Mode based

   Gestures

   Tool palette for strokes, colour
Harold: A world made of drawings
(Cohen, Hughes, Zeleznik)

Advantages:
   Easy to implement and use
   Rapid placement of features




Disadvantages:
   Not true 3D – A billboard of a house ruins the illusion
   Terrain looks odd from angles other than creation angle
A sketching interface for terrain modeling
(Watanabe, Igarashi – Siggraph '04 poster)




   More natural terrain profiles
   Each stroke creates a mountain
   Segment stroke at local maxima/minima
   Create cross-sectional shape and depth for each segment
Terrain – Outstanding problems (not exhaustive):
   Mountains created along a line parallel to view-plane
   A real mountainous horizon silhouette contains many peaks
from different ranges at different depths
SmoothSketch: 3D free-form shapes from
complex sketches
(Karpenko, Hughes – Siggraph '06)

Aim:
Infer plausible 3D free-form shapes from visible-contour sketches

Approach:
Infer hidden contours

Assume low curvature




A similar approach could work for terrain
Flowers, Plants & Trees




    Three recent papers
Floral diagrams and inflorescences: Interactive flower
modeling using botanical structural constraints
(Ijiri, Okabe, Owada, Igarashi – Siggraph '05)


 Aim:
 To model flowers quickly in 3D via a progression of specialised interfaces

 Approach:

 Separate structure and geometry modelling

 Limited enough to restrict problem space

 General enough to allow user creativity

 Specific user interface for each component
Floral diagram editor


                        Inflorescence structure & geometry editor




Petal modelling
Floral diagrams and inflorescences: Interactive flower
modeling using botanical structural constraints
(Ijiri, Okabe, Owada, Igarashi – Siggraph '05)


Summary:

A good example of an application specific interface with
some sketch based components

   Limited to 8 common branching patterns for flower heads

Sketching only used for geometry, structure is created by


modifying handles on template arrangements
Interactive Design of Botanical Trees Using Freehand
Sketches and Example-based Editing
(Okabe, Owada, Igarashi – EG '05)

 Aim:
 To quickly design 3D trees
 based on 2D sketching and
 example based control.
Interactive Design of Botanical Trees Using Freehand
Sketches and Example-based Editing
(Okabe, Owada, Igarashi – EG '05)


Approach:
Sketch branch structure




Gestural, mode based branch editing




Example based leaf arrangement

Interactive Design of Botanical Trees Using Freehand
Sketches and Example-based Editing
(Okabe, Owada, Igarashi – EG '05)

                                    Assume user only draws
                                    branches extending sideways
                                    Place branches in 3D by

                                    calculating rotation around
                                    trunk to maximize inter-branch
                                    distance
Interactive Design of Botanical Trees Using Freehand
Sketches and Example-based Editing
(Okabe, Owada, Igarashi – EG '05)


 Summary:

 Rapid tree creation

 Some natural principles ignored (tropism)

 Appearance more important than close simulation of reality

 Sketching used to generate tree structure and leaf
 geometry (in contrast to previous paper)
Modeling Plant Structures Using Concept Sketches
(Anastacio, Costa Sousa, Samavati, Jorge – NPAR '06)

 Aim:
 To allow rapid modeling of simple spiral plant arrangements
Approach:
Build plant structure from sketched construction lines.

Leaf variety by interpolation between extreme cases

Pen and ink rendering
Different phyllotactic patterns




 Combining two
 structures
Modeling Plant Structures Using Concept Sketches
(Anastacio, Costa Sousa, Samavati, Jorge – NPAR '06)


  Summary
     Limited to single compound plant structures (no branching)
     Limited to spiral arrangement
     Lends itself to a multi-resolution approach to modeling
                       Summary
What have we seen?

High level -> Concept sketches
vs
Low level -> geometry editor

Reducing user work through example based editing

Sketching works nicely given a-priori knowledge of the domain

None of this work uses L-Systems

				
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posted:8/23/2011
language:English
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