Sungmin Kim
SEOUL NATIONAL UNIVERSITY
Fashion Technology5. 3D Garment CAD-1
Garment Design
• Body modeling• 3D draping simulation
Pattern Design
• 2D Parametric design• 3D pattern design
Fabric Design
• Weave CAD• 2.5D Mapping
Flat Sketch
• Scalable vector graphics• Feature-based design
Design Process
Overview
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DesignProcess
3-D Graphics
Surface Graphics Representation of Objects using Surface Geometry
Uses polygonal mesh for modeling objects
Processing speed depends on scene complexity
Easy for hardware acceleration
Used for most computer graphics applications
Hybrid application with raster graphics
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3-D Graphics
Surface Graphics Triangular Mesh Structure
Collection of triangular elements (vertices + edges)
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face normalvector
3-D Graphics
Volume Graphics Voxel (Volume Element) based
Space division method
Independent processing with scene complexity
Hardware acceleration method has not been established
Used for medical applications
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3-D Graphics
Lighting Importance
Lighting enhances the reality of scene
Realistic appearance may be a crucial factor for specific application
Difficulties
Effects of various light sources and colors
– Sun, fire, light bulb, ...
Effects of material surface property and color
– Shiny, dull, ...
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3-D Graphics
Lighting Light Sources
Directional (Parallel)
Ambient (Incident)
Spot (Specular)Point
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3-D Graphics
Lighting
Ambient Lighting
Effect of indirect lighting
Realization of color
Diffuse Lighting
Shading effect
Specular Lighting
Creating highlights
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3-D Graphics
Shading Evaluation of Lighting Equation
Calculate for each vertex on the mesh
Interpolate for the rest of the mesh
Type
Flat shading
Gouraud shading
Phong shading
Flat Shading
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TriangularElement
Face normal vector
LightAngle
3-D Graphics
Shading Gouraud Shading
Evaluate color at each vertex
Interpolate the color of interior points
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Barycentric Coordinate System
3-D Graphics
Shading Phong Shading
Interpolate normal vectors for interior points
Evaluate lighting equation for each point
More accurate shading
Realization of specular light (highlight)
InterpolatedNormal vector
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3-D Graphics
Texture Mapping Importance
Enhance visual quality of object without increasing scene complexity
Procedure
Prepare 2D texture image
Assign texture coordinates to each vertex
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3-D Graphics
Rendering Global Illumination
Color is determined by multiple interactions among light sources and reflective surfaces
Recursive reflection of light between surfaces accounts for subtle shading
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3-D Graphics
Rendering Ray Tracing
Rendering technique that mimics the physical processes of light
Extremely intensive computation
– Transparency, refraction, reflection, shadow...
– Real-time ray-tracing became possible since 2018
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Geometric Modeling
Preparation of 3D Objects
Using Modeling Software Packages
3D Studio Max
Maya
Rhino 3D
Z-Brush
From 3D Scan Data
RapidForm
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Geometric Modeling
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Wireframe Modeling System Wireframe Model
Represents a shape by its characteristic lines and end points
Uses lines and points to display three-dimensional shapes
Allow manipulation of the shapes by modifying the lines and points
Mathematical Description
List of curve equations, coordinates of the points, and connectivity information for the
shape’s curves and points
Weakness
Visual ambiguity
Lack of 3D information
Geometric Modeling
Surface Modeling System Surface Model
Represents a model by its surface geometry
Mathematical Description
List of surface equations and curve equations
Surface connectivity
Modeling Method
Interpolating the input points
Interpolating the curve nets specified
Translating or revolving a specified curve
Purpose
Aesthetic evaluation of visual model
Generation of NC tool paths
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Geometric Modeling
Solid Modeling System Solid Model
Represents a shape having a closed volume, called a solid
Mathematical Description
Information that determines whether any location is inside, outside or on the closed volume
Advantage
Any information related to the volume of the solid can be derived
Application program can be written to do operation at the level of volume instead of at the
level of surface
– Automatic generation of finite elements
– Volumetric NC tool path generation
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Geometric Modeling
Nonmanifold Modeling Nonmanifold Model
Model of mixed dimensions
– A wire edge emanating from a point on a surface
– Faces forming a cellular structure
Useful for abstract and/or intuitive design
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Geometric Modeling
Solid Modeling Methods
Modeling by simple solids
– Primitive creation, Boolean operation
Modeling by moving a surface
– Sweeping, skinning, swinging
Modeling by modifying existing shapes
– Rounding, lifting, lower level entity editing, boundary modeling
Modeling with range data
– Skinning
Parametric modeling
Feature-based modeling
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Geometric Modeling
Solid Modeling Primitive Creation
Procedure
– Retrieve a simple shape from the solids stored in advance
– Create a solid of the same shape with the size specified by user
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Geometric Modeling
Solid Modeling Boolean Operation
Procedure
– Combine primitives in some ways to create a new shape
– Union, intersection, and difference is mostly used
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Geometric Modeling
Solid Modeling Sweeping
Procedure
– A planar closed domain is translated or revolved to form a solid
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Geometric Modeling
Solid Modeling Skinning
Procedure
– Form a closed volume or a solid by creating a skin surface over prespecified cross-sectional planar
surfaces
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Geometric Modeling
Solid Modeling Parametric Modeling
Procedure
– Model a shape by solving geometric constraints
» The relation between the elements
» The dimension data
» The relations between the dimensions
– Construct the shape by solving multiple constraint equations
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Geometric Modeling
Data Structure B-Rep (Boundary Representation)
Features
– Stores the boundary of a solid using vertices, edges, and faces
– Includes connectivity information
Types
– Half-edge structure
– Winged-edge structure
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Geometric Modeling
Data Structure Decomposition
Voxel representation
– Three dimensional extension of a raster representation
– Used for the calculation of mass property of a solid
– May require a great deal of memory space
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3D Pattern Design
Pattern Design Methods
Pattern Design
Trial-and-error
Time consuming
Labor dependent
Subjective
Reusable script
Complex design
Database
Intuitive design
Simple design
Reproducible
Interactive Script
AutomaticGeneration
ManualDesign
3-D2-D
Draping design
Order-made
Custom design
Template based
Surface peeling
Garment modeling
AutomaticManual
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3D Pattern Design
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Body surface
Surface Peeling
Parametric design
Garment Modeling
Ideal garment
Template
Shape matching
Template Based
Template Based
Structured Mesh Model Preparation
Prepare the desirable shape of garment with structured mesh
Capture the shape of garment using stereovision method
Reconstruct a structured garment model
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Left Image
Right Image
Stereovision Algorithm
Panel reconstruction Garment Template
Template Based
Overview
Measured Body
Ideal Garment Shape
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Shape Matching
Projection
Template Based
Shape Matching
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Based on the corresponding landmarks defined on body and garment model
Initial Alignment
Coordinates of some points on the garment model need to be fixed for design features
Form Design Features
Points on the garment model are moved to form a convex hull of underlying body
Convex Hull Generation
Template Based Template Based Method
Body Shape Independent Pattern Generation
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Normal
Fat and Stoop
Template Based
Mesh structure refinement
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Low Resolution High Resolution
Template Based
Stripwise 2D Development 2D Projection Method #1
Consideration of fabric physical properties
Automatic dart generation
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A B
New point
New point
Spatial ElementInitiallly Setteled
SideNew point byside lengths
Repetition
Within tolerance
Template Based
Stripwise Development Effect of Different Conditions
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Different mesh resolution Different elastic tolerance
