05計(jì)算機(jī)圖形學(xué)-雙語(yǔ)課程

ObjectivesLearn

the

basic

design

of

a

graphicssystemIntroduce

pipeline流水線architectureExamine

software

components

for

aninteractive

graphics

systemImage

FormationRevisitedCan

wemimic模仿thesynthetic

cameramodel

to

design

graphics

hardwaresoftware?Application

Programmer

Interface

(API)Need

only

specifyObjects對(duì)象Materials材質(zhì)屬性Viewer觀察者Lights光源But

how

is

the

API

implemented?PhysicalApproachesRay

tracing光線

:

follow

raysof

light

fromcenter

of

projection

until

they

either

areooff

to

infinity無(wú)窮遠(yuǎn)absorbedbyobjectsCan

handle

global

effectsMultiple

reflectionsTranslucent半透明objectsSlow-

Must

have

wholedata

baseavailable

at

all

timesRadiosity輻射度:Energy

based

approach-

VeryslowPhysical

Approaches

?(The

answer

is

no)Let’s

see

the

GraphicsArchitecturesOutline１.６

TheProgrammer’s

Interface1.6.1

Three-Dimensional

APIs1.7

Graphics

Architectures1.7.1

Display

Processors1.7.2

Pipeline

Architecture1.7.3

The

Graphics

Pipeline1.7.4

Vertex

Processing1.7.5

Clip and

Primitive

Assembly1.7.6

Rasterization1.7.7

Fragment

Processing１.６

The

Programmer’sInterfaceProgrammerseesthe

graphicssystemthrough

a

software

interface:

the

ApplicationProgrammer’s

Interface

(API)Fig

1.21

Application

Programmer’s

model

of

graphics

system1.6.1

Three-DimensionalAPIs(API

Contents)Functions

thatspecify

what

we

needtoforman

imageObjects對(duì)象Viewer觀察者Light

Source(s)光源Materials材質(zhì)屬性O(shè)therinformationInput

from

devices

such

as

mouse

and

keyboardCapabilities

of

system1.6.1

Three-Dimensional

APIs（Object

Specification對(duì)象指定）Most

APIs

support

a

limited

set

of

primitivesincludingPoints

(0Dobject)Line

segments(1D

objects)Polygons

(2D

objects)Some

curves

andsurfacesQuadrics二次曲面Parametric

polynomials

參數(shù)多項(xiàng)式曲面All

are

defined

throughlocations

in

space

空間位置orVertices頂點(diǎn)1.6.1

Three-DimensionalAPIs（Example）glVertex3f(0.0,0.0,0.0);glVertex3f(0.0,1.0,0.0);glVertex3f(0.0,0.0,1.0);glEnd(

);type

ofobjectlocation

of

vertexglBegin(GL_POLYGON)end

of

object

definition1.6.1

Three-DimensionalAPIs（Camera

Specification,

Viewer觀察者）Six

degrees

offreedomPosition位置of

center

oflens鏡頭,COPOrientation方向Lens鏡頭focal

lengthFilm

plane膠片平面sizeOrientationFig

1.25

camera

specification1.6.1

Three-DimensionalAPIs(Lights光源)Types

oflightsPoint

(Positional)sources點(diǎn)光源vs

distributed

(Directional)sources分布光源Spot

lights聚光源Near

and

far

sources近光遠(yuǎn)光Color

properties1.6.1

Three-Dimensional

APIs(Materials材質(zhì)屬性)Material

propertiesAbsorption吸收:color

propertiesScattering散射Diffuse漫反射Specular鏡面反射1.7 GraphicsArchitecturesEarly

graphics

systems

used

general-purpose

computers.CPUSystemMemory

ControllerMonitorSystem

BusI/ODevicesDigital

to

og(D/A)converter1.7.1

Display

ProcessorsSpecial-purposegraphics

systems,

relieving

thegeneral-purpose

computer

from

the

task

ofrefreshing

the

displaycontinuously.CPUSystemMemoryControllerSystem

BusI/O

DevicesDisplay

Processormemory(FrameBuffer)ControllerMonitorDisplay

listDisplay

ProcessorRather

than

have

the

host

computer

try

torefresh

display

use

a

special

purpose

computercalled

a

display

processor

(DPU)Graphics

stored

in

display

list顯示列表(displayfile)

on

display

processorHost

compiles

display

list

and

sends

to

DPU1.7.2 Pipeline

ArchitecturePipeline流水線Concurrency并行Delayor

latency延遲Throughput吞吐量1.7.3

The

Graphics

Pipeline(Practical

Approach)Process

objects

one

at

a

time

in

the

order

theyare

generated

by

the

applicationPipelinearchitectureAll

steps

can

be

implemented

in

hardware

onthe

graphics

cardapplicationprogramdisplay1.7.4

VertexProcessing頂點(diǎn)處理Vertex頂點(diǎn)包含拓?fù)湫畔⒃趦?nèi)的幾何表示拓?fù)湫畔opology，鄰接關(guān)系、次序幾何信息Geometry，點(diǎn)（一般意義的點(diǎn)point）坐標(biāo)信息Vertex頂點(diǎn)及其頂點(diǎn)序列構(gòu)成線段，多邊形，或者

多邊形集合曲線、曲面

的參數(shù)頂點(diǎn)圖形學(xué)中最基本的幾何模型1.7.4

VertexProcessing頂點(diǎn)處理Much

of

the

work

in

the

pipeline

is

inconvertingobject

representations(幾何階段)from

onecoordinate

system

toanotherObjectcoordinates對(duì)象坐標(biāo)Camera

(eye)coordinates觀察坐標(biāo)Screen

coordinates屏幕坐標(biāo)Every

change

of

coordinates

is

equivalent

to

amatrix矩陣transformationVertex

processor

also

computes

vertex

colors1.7.4

Vertex

Processing(Projection投影)Projection投影is

the

process

thatcombines

the3D

viewer

with

the

3Dobjects

to

produce

the

2D

imageprojections:all

projectors投影線meet

at

the

center

of

projection投影中心Parallel平行projection:projectors投影線areparallel,center

of

projection

is

replaced

by

a

direction

of

projection投影方向1.7.4

Vertex

Processing(Projection投影)Chapter

5

will

discuss

projection

processComputer

viewingprojectionsParallel

projectionChapter

6

will

discuss

lighting

andshading光照與明暗繪制computes

vertex

colors1.7.5

Clipand

Primitive

Assembly裁減與圖元組裝(Primitive

Assembly)Vertices

must

be

collected

into

geometricand

rasterizationobjects

before

clipcan

takeplaceLinesegments線段Polygons多邊形-Curves

and

surfaces

曲線曲面1.7.5

Clipand

Primitive

Assembly(Clip

裁減)Just

asa

realcamera

cannot

“see”thewhole

world,

thevirtual

camera

can

onlysee

partof

the

world

or

object

space-

Objects

that

are

notwithinthis

volume

are

saidto

be

clipped

out

of

the

scene1.7.5

Clipand

Primitive

Assembly(Clip

)Chapter

7

(7.3,

7.4,

7.5,

7.6,

7.7)

willdiscuss

Clip

processClipLine

segments

ClipPolygonclipClipClipof

other

primitivesin

threedimensions1.7.6

Rasterization光柵化If

an

object

is

not

clippedout,

the

appropriatepixels

in

theframebuffer

must

be

assignedcolorsRasterizer

produces

a

set

offragments片元foreach

objectFragments

are“potential潛在pixels”Havealocation

inframe

buffer位置信息Color

attributes顏色屬性Depth

information深度信息Vertex

attributes

are

interpolated

over

objects

bytherasterizer1.7.6

Rasterization光柵化Chapter

7

(7.8,

7.9,

7.10)

will