SEOUL NATIONAL UNIVERSITY

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1 Fashion Technology 5. 3D Garment CAD-1 Sungmin Kim SEOUL NATIONAL UNIVERSITY Overview Design Process Concept Design Scalable vector graphics Feature-based design Pattern Design 2D Parametric design 3D pattern design Design Process Fabric Design Weave CAD 2.5D Mapping Garment Design Body modeling 3D draping simulation 2

3-D Graphics Surface Graphics Representation of

for modeling objects Processing speed depends on

Used for most computer graphics applications Hybrid

Surface Graphics Triangular Mesh Structure

2 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 3 3-D Graphics Surface Graphics Triangular Mesh Structure Collection of triangular elements (vertices + edges) face normal vector 4

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

3 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 5 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,... 6

4 3-D Graphics Lighting Light Sources Directional (Parallel) Point Spot (Specular) Ambient (Incident) 7 3-D Graphics Lighting Ambient Lighting Effect of indirect lighting Realization of color Diffuse Lighting Shading effect Specular Lighting Creating highlights 8

Triangular Element Flat Shading 9 3-D Graphics Shading Gouraud Shading Evaluate color at each vertex

5 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 Face normal vector Light Angle Triangular Element Flat Shading 9 3-D Graphics Shading Gouraud Shading Evaluate color at each vertex Interpolate the color of interior points c2 c3 a1 C a2 a3 c1 c1 a1 c2 a2 c3 a3 C a1 a2 a3 Barycentric Coordinate System 10

3-D Graphics Shading Phong Shading Interpolate normal vectors for

accurate shading Realization of specular light (highlight)

Importance Enhance visual quality of object without increasing

6 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) Interpolated Normal vector 11 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 12

$shading Type Ray casting Ray tracing 13 3-D Graphics Rendering Ray Tracing Rendering technique that mimics the physical processes of light Extremely intensive computation Transparency Refraction and$

7 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 Type Ray casting Ray tracing 13 3-D Graphics Rendering Ray Tracing Rendering technique that mimics the physical processes of light Extremely intensive computation Transparency Refraction and reflection Lighting and shadow 14

8 Geometric Modeling Preparation of 3D Objects Using Modeling Software Packages 3D Studio Max Maya SoftImage LightWave From 3D Scan Data RapidForm 15 Geometric Modeling 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 16

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

9 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 17 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 18

10 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 19 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 20

11 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 21 Geometric Modeling Solid Modeling Boolean Operation Procedure Combine primitives in some ways to create a new shape Union, intersection, and difference is mostly used 22

12 Geometric Modeling Solid Modeling Sweeping Procedure A planar closed domain is translated or revolved to form a solid 23 Geometric Modeling Solid Modeling Skinning Procedure Form a closed volume or a solid by creating a skin surface over prespecified cross-sectional planar surfaces 24

13 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 25 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 26

Geometric Modeling Data Structure Decomposition Voxel representation Three dimensional extension

great deal of memory space 27 3D Pattern Design Pattern Design Methods Pattern Design 2-D 3-D

dependent Objective Interactive Intuitive design Simple design Reproducible Script Reusable

14 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 27 3D Pattern Design Pattern Design Methods Pattern Design 2-D 3-D Manual Design Automatic Generation Manual Automatic Trial-and-error Time consuming Labor dependent Objective Interactive Intuitive design Simple design Reproducible Script Reusable script Complex design Database Draping design Order-made Custom design Template based Surface peeling Garment modeling 28

15 3D Pattern Design Template Based Surface Peeling Garment Modeling Ideal garment Template Body surface Parametric design Shape matching 29 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 Left Image Right Image Stereovision Algorithm Panel reconstruction Garment Template 30

16 Template Based Overview Ideal Garment Shape Projection Shape Matching Measured Body 31 Template Based Shape Matching Initial Alignment Form Design Features Convex Hull Generation Based on the corresponding landmarks defined on body and garment model Coordinates of some points on the garment model need to be fixed for design features Points on the garment model are moved to form a convex hull of underlying body 32

17 Template Based Template Based Method Body Shape Independent Pattern Generation Normal Fat and Stoop 33 Template Based Mesh structure refinement Low Resolution High Resolution 34

Setteled Side New point by side lengths Repetition A B Within tolerance 35 Template Based

18 Template Based Stripwise 2D Development 2D Projection Method #1 Consideration of fabric physical properties Automatic dart generation New point New point Spatial Element Initiallly Setteled Side New point by side lengths Repetition A B Within tolerance 35 Template Based Stripwise Development Effect of Different Conditions Different mesh resolution Different elastic tolerance 36

L1 - Introduction. Contents. Introduction of CAD/CAM system Components of CAD/CAM systems Basic concepts of graphics programming

L1 - Introduction. Contents. Introduction of CAD/CAM system Components of CAD/CAM systems Basic concepts of graphics programming L1 - Introduction Contents Introduction of CAD/CAM system Components of CAD/CAM systems Basic concepts of graphics programming 1 Definitions Computer-Aided Design (CAD) The technology concerned with the