1 review of compsci 221 chapters 1-11 in text user interfaces will be addressed as a take- home...

1Zhang & Liang, Computer Graphics Using Java 2D and 3D (c) 2007 Pearson Education, Inc. All rights reserved.

Review of COMPSCI 221

Chapters 1-11 in text User Interfaces will be addressed as a take-

home question


Computer Graphics

Modeling: Creating a virtual world.

Rendering: Generating a visual image of a scene.

Rendering

Virtual world model Image of a scene


Java2D

Graphics2D class manages the rendering Use a Panel to provide the Graphics context Use JApplet or JFrame as root container


Graphics2D Class

Properties– Foreground color– Font– Stroke– Paint

Capabilities– drawing and filling Shape objects– applying AffineTransforms


2D Objects

A 2D object consists of a set of points in a plane

Examples– point– lines, curves– shapes like rectangles, ellipses, arcs, polygons– text and images


Parametric Equation

Parametric equation expresses each coordinate in terms of a parameterx = f(t)

y = g(t) The parametric equation for an ellipse is

x = x0 + a cos t

y = y0 + b sin t


Custom Shapes

Area combines shapes to create more complex objects

Set-theoretic operations– Intersect– Add– Subtract– Exclusive or

PathIterator interface allows Shape object to return an iterator to sub-parts

Path2D constructs an outline from a sequence of lines and curves – moveTo

– lineTo

– quadTo

– curveTo

– closePath


Coloring Objects

Paint interface supports – Color - create a color by giving the amount od

red, green, blue to make the color– Gradients - interpolations between two different

colors– Texture - use an image to "color" an object


Strokes The Stroke interface defines a method for

creating an outline from a shape BasicStroke class has the following

properties– Width– End style (butt, round, square)– Join style (bevel, miter, round)– Miter limit (limits miters on small angle joins)– Dash pattern and phase


Affine Transformation

Maps parallel lines to parallel lines Common affine transforms in both 2D and

3D– Translation– Rotation– Reflection– Scale– Shear


Clipping Path

A rendered image may be clipped by a clipping path


Text in Java2D

Text is treated as a special kind of geometric object

A Font defines the rendering shapes of all the characters

Geometry of a text string in a particular font is represented by a GlyphVector

Create a Shape from the GlyphVector


BufferedImage

A BufferedImage contains – Raster -- holds the pixel

values– ColorModel -- specifies

how to interpret pixel values

BufferedImage has a createGraphics method which allows you to draw to the image

BufferedImageOps– RescaleOp - scale pixel

values linearly

– LookupOp - use a table to convert pixel values

– ConvolveOp - convolute pixel value with thos of neighbors

– ColorConvertOp - pixel-by-pixel color conversion

– AffineTransformOp - apply the specified transformation to each pixel


Animation

You need a way to make something happen at regular intervals– Change some parameter used by the paintComponent

method– call repaint() or revalidate() to cause paintComponent

to be called Timer is a Swing Component

– delay can be set– generates an ActionEvent after each delay period– register a Listener to respond to the event


3D Model and View


Java 3D

High-level API Scene is represented

as a scene graph object– Content branch defines

the onjects in the scene

– View branch defines how the scene is viewed

VirtualUniverse– SimpleUniverse

Locale Nodes

– Group nodes– Leaf nodes

NodeComponents– attached to one or more

nodes


Background and Bounds

Default background is black Create custom background with the Background node

– set the color

– use an image

– use a geometry

Environmental nodes need to be limited in extent– e.g. lights, background

– limits amount of rendering to be done

Two ways:– Bounds, node component

– BoundingLeaf, a Node uses a Bounds object


Points and Vectors

Point represents position Vector represents

direction Both can be represented as

a tuple An n-dimensional vector

is an n-tuple of numbers– (x1, x2, …, xn)


Shapes in 3D

Use a Shape3D Node to represent visual objects– A Shape3D leaf node

usually references Geometry and Appearance node components

Geometry is abstract class with many subclasses– GeometryArray

– IndexedGeometryArray

– Text3D


GeometryArray

Supports construction of objects using arrays of points, lines and polygons

Defines an array of vertices along with other properties that are associated with them– normals– color (3 or 4 elements)– texture coordinates (2, 3 or 4 elements)


Transform3D

A higher-level representation for transformations

Has constructors to create from both Matrix objects and from vectors

Also has set and get methods for the internal 4x4 matrix

Can also set a particular type of transformation


Views

View Volume– represented by a

projection matrix

View positioning– represented by a view

matrix

View Properties– Projection type

– Field of view

– Limits to view distance

– Size of view plate


Projections A projection maps a point in the virtual

world onto a view plane– view plate is a finite window in the view plane– also limit the depth that is rendered

Two types of projection– parallel– perspective


Types of Lights

Ambient light– uniform in all

directions and locations

Directional light– models a distant light

source whose rays are all parallel

Point light– light located at a

particular location which emits in all directions

– Intensity decreases with distance

Spot light– Like a point source

except the direction of the emission is restricted


Geometry of Reflection For perfectly reflective surface

– angle of incidence = angle of reflection

– no loss of intensity

In reality surfaces aren't perfect – light gets scattered

– light can be absorbed

Phong modelI = Iaka + Ipkd cos + Ipkscosn

– ka, kd, ks are coefficients for ambient, diffuse and specular reflection for a particular material

– n is the shininess coefficient, also a property of the material


Appearance

Node component which has components that control various aspects of the appearance of an object.– ColoringAttributes, RenderingAttributes,

TransparencyAttributes

– PointAttributes, LineAttributes, PolygonAttributes

– Material

– TextureAttributes, Texture, TexCoordGeneration, TextureUnitState


Material Contains components to control the color

contributed by different kinds of lighting– ambient, diffuse, specular– can also contain an emissive color component

Shininess coefficient affects specular reflection

Color target for per-vertex colors


Depth Cueing

Atmospheric attenuation effects can be simulated with depth cueing

Blend the objects with background color (or with arbitrary fog color)C = f C0 + (1 - f) Cf

Blending is an increasing function of the distance– linear– exponential– gaussian


Texture Mapping

Real surfaces often have a large amount of detail

Use a digital image to provide complex detail with minimal computational cost

Procedural textures use a function to calculate the color at any given point


Behavior

Java3D uses behavior to facilitate dynamics in a scene graph

Behavior is a leaf node– Defines actions to be taken when the behavior

is activated (waked-up)– Behavior is triggered by wakeup conditions

For interactions, triggers are user generated For animation, triggers are time-based


Interpolators for Animation

Interpolator is an abstract subclass of Behavior– It has a number of predefined subclasses containing

typical behaviors needed for animation For example, Color, Switch, Transparency, Transform

The idea is to set two values for a particular attribute and interpolate values in between as a function of time

Alpha object is used to trigger the changes


Alpha

A function of time – usually periodic

Has a range from 0.0 to 1.0


User Interfaces

Design principles– User should be in

control

– Reduce memory load for users

– Be consistent

Useability heuristics– Ease of learning and

remembering

– Efficiency of use

– Minimize errors Facilitate recovery from

errors

1 review of compsci 221 chapters 1-11 in text user interfaces will be addressed as a take- home...

Documents

pixel slide

glyphvector slide

view slide

phase slide

images slide

affinetransforms slide

event slide

clipping path slide