Disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM Graphics modeling.

disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM

Graphics modeling


Class schedule

• Monday – 11.00 – 12.50 (makmal GIS)

• Thursday – 12.00 – 12.50


review

• What have you learnt in ASAS GRAFIK KOMPUTER?.


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


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


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)


• 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


Application

• Computer Aided Design/ engineering (CAD/CAE)

• Entertainment– Special effects– Animation– games

• Scientific visualization• Education, information, advertising


CAD/CAE

• Stages– Conceptual design– Mechanical design– Simulation– Production

• Geometric data need to be shared


CAD/CAE

• Conceptual design


CAD/CAE

• mechanical design


CAD/CAE

• simulation


Special effect

• Merge real and virtual objects

• Create virtual scenes indistinguishable from reality


animation


games

• Adventure - interactive


visualization

geographicalmedical

Bio-geometric


Requirement : Visualization

• Space efficiency

• Generality

• Precision

• Support fast algorithms


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.


Requirement : animation and special effects

• Generality – all kinds of natural and artificial objects

• Flexibility – let animator make choices

• Support high-quality rendering

• “semiautomatic” acquisition.


Requirements : games and VR

• Interactive games– Support for interactive rendering crucial– Models should be small– Easy to animate– Procedural generation


Existing software

• 3DS Max

• Maya

• Rhino


Applicable mathematical technique

• Linear algebra

• Vectors

• Matrix methods

• Determinants

• Set theory

• Polynomial interpolation

• Numerical approximation


Geometric modeling scheme

• Wire-frame model

• Surface model

• Solid model


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


• Example : tetrahedron

Wire-frame model


Disadvantages of wire-frame• Tend to be not realistic

• Ambiguity – complex model difficult to interpret.

What does this object look like?


Disadvantages of wire-frameWhich object does the previous wire-frame represent?

The use of shading and hidden surface removal technique can improve the rendition.


• 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


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.


Surface model

• An area bounded by an identifiable perimeter.

• In Computer Graphics, is an area within which every position is defined by mathematical method.


Surface model


Surface may be:

– Planar

– Cylindrical/conic

– Sculptured or freeform in shape

Surface model


• 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


•Does not represent internal features of

the model, no sense of volume.

•Models of limited value for volumetric and mass property analysis.

Surface model


Solid model

• Most complex

• Complete representation

• unambiguous description

• Appropriate for the world of engineering objects


Solid model


Step from geometric to program

• Geometry algebra algorithm program

representation

-Symbolic-Numerical-approximation

Disediakan oleh Suriati bte Sadimon GMM, FSKSM, UTM Graphics modeling.

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