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disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Class schedule
• Monday – 11.00 – 12.50 (makmal GIS)
• Thursday – 12.00 – 12.50
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
review
• What have you learnt in ASAS GRAFIK KOMPUTER?.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
What is geometric modeling?
• Collection of methods used to define the shape and other geometric characteristics of an object.
• To construct a precise mathematical description of the shape of a real object or to simulate some process.
• Embraces area – computational geometry
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
What is geometric modeling?
• special case of mathematical modeling• the visual features are important.• geometric model - physical object.• non-geometric model – physical process e.g economic
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Geometric data
• To make pictures/ design new things need a computer representation of objects.
• Need to represent– Shape– Appearance (color, shininess etc)– Material properties (density, stiffness etc)
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
• Geometric data representation- Compute a mathematical approximation of the physical
shape of an object
• Algorithms for manipulating geometry– Manipulate the variables defining the shape until we
meet the objective.
• Geometry creation– Interactive.
– Automatic creation.
geometric modeling
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Application
• Computer Aided Design/ engineering (CAD/CAE)
• Entertainment– Special effects– Animation– games
• Scientific visualization• Education, information, advertising
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
CAD/CAE
• Stages– Conceptual design– Mechanical design– Simulation– Production
• Geometric data need to be shared
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Special effect
• Merge real and virtual objects
• Create virtual scenes indistinguishable from reality
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Requirement : Visualization
• Space efficiency
• Generality
• Precision
• Support fast algorithms
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Requirement : CAD/CAE
• Precision is very important
• Integrate additional data
• Smooth surfaces
• Algorithms for thermal/stress simulation, tool path generation etc.
• Automatic acquisition for reverse engineering.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Requirement : animation and special effects
• Generality – all kinds of natural and artificial objects
• Flexibility – let animator make choices
• Support high-quality rendering
• “semiautomatic” acquisition.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Requirements : games and VR
• Interactive games– Support for interactive rendering crucial– Models should be small– Easy to animate– Procedural generation
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Applicable mathematical technique
• Linear algebra
• Vectors
• Matrix methods
• Determinants
• Set theory
• Polynomial interpolation
• Numerical approximation
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Geometric modeling scheme
• Wire-frame model
• Surface model
• Solid model
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Wire-frame model
• The shape of the object is defined by a collection of points (vertices) and a set of edges.
• Edges – line or curved connects pair of points
• Conventional Approach - Place the geometry entirely in the data structure.
• Another Approach - Procedural Approach
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Disadvantages of wire-frame• Tend to be not realistic
• Ambiguity – complex model difficult to interpret.
What does this object look like?
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Disadvantages of wire-frameWhich object does the previous wire-frame represent?
The use of shading and hidden surface removal technique can improve the rendition.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
• Does not allow for use of photo realistic rendering tools. *(some software capable of hidden line removal on limited basis).
• No ability to determine computationally information on mass properties (e.g volume, mass, moment etc) and line of intersect between two faces of intersecting models.
• No guarantee that the model definition is correct, complete or manufacturable.
Disadvantages of wire-frame
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Advantages of wire-frame
• Easy to construct
• Most economical in term of time and memory requirement.
• Used to model solid object.
• Often used for previewing objects in an interactive scenario.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Surface model
• An area bounded by an identifiable perimeter.
• In Computer Graphics, is an area within which every position is defined by mathematical method.
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Surface may be:
– Planar
– Cylindrical/conic
– Sculptured or freeform in shape
Surface model
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
• To overcome ambiguity in wire-frame model
•used for the generation of visually
realistic images through techniques
such as
•rendering
•hidden edge removal.
Surface model
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
•Does not represent internal features of
the model, no sense of volume.
•Models of limited value for volumetric and mass property analysis.
Surface model
disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM
Solid model
• Most complex
• Complete representation
• unambiguous description
• Appropriate for the world of engineering objects