Learn OpenGL: Learn modern OpenGL graphics programming in a step-by-step fashion.

525 Pages·2020·54.684 MB·English

by  Joey de Vries

Theonlineversionofthistextlivesatlearnopengl.com.
Copyright c 2020byJoeydeVries
(cid:31)
ALLRIGHTSRESERVED
Thelayoutandstylingofthisbookisbasedonthepublic’LegrandOrangeBook’LaTeXtemplate
byVel.
Firstprinting,June2020
ISBN:978-90-90-33256-7
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
I Getting started
2 OpenGL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Creating a window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Hello Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5 Hello Triangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6 Shaders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
7 Textures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
8 Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
9 Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
10 Camera. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
11 Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
II Lighting
12 Colors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
13 Basic Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
14 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
15 Lighting Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
16 Light Casters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
17 Multiple lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
18 Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
III Model Loading
19 Assimp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
20 Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
21 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
IV Advanced OpenGL
22 Depth Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175
23 Stencil testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
24 Blending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
25 Face culling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
26 Framebuffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
27 Cubemaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
28 Advanced Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226
29 Advanced GLSL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
30 Geometry Shader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242
31 Instancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256
32 Anti Aliasing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
V Advanced Lighting
33 Advanced Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
34 Gamma Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
35 Shadow Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
36 Point Shadows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
37 Normal Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
38 Parallax Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
39 HDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338
40 Bloom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
41 Deferred Shading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .353
42 SSAO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366
VI PBR
43 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
44 Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .396
45 Diffuse irradiance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405
46 Specular IBL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420
5
VII In Practice
47 Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .440
48 Text Rendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452
VIII 2D Game
49 Breakout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .462
50 Setting up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464
51 Rendering Sprites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
52 Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .473
53 Ball . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .480
54 Collision detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .483
55 Collision resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .489
56 Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .495
57 Postprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501
58 Powerups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506
59 Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .513
60 Render text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .515
61 Final thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .523
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .525
Firstofall,awarmthankyouforpurchasingthisbook. Thecontentofthisbookoriginally
started outas digital letters onthe online platformat learnopengl.com. LearnOpenGL quickly
evolvedfromaseriesoftutorials, toafullonlinebookwithyearsofcontinuousfeedbackand
improvementsthatarenowfinallyaggregatedintothephysicalcopyyouholdinyourhands.
Theonlineversionatlearnopengl.comisfree,andwillalwaysbefree,andforthemostupto
datecontentandquestionsfromreadersitisstilladvisedtosearchuparticlesontheonlineplatform.
However,aphysicalcopymakesiteasytoreadduringtravel,writenotes,andweshouldneverforget
thatcertaincharmofprintedpaper.Andnottoforget,purchasingaphysicalcopyhelpssupportme
asanauthorforwhichIagainthankyoufromthebottomofmyheart.
Thebookisstructuredsimilarlytotheonlineplatform,withafewminordifferencestoaccount
forthebookbeingoffline.Thinkofalargereductionofhyperlinks,hyperlinksbeingfullywritten
out,videosnowshowingstaticimages,andthelackoffunctionhoverpop-ups. Thecontenthas
howeverbeenthoroughlyrevised,andreviewedmultipletimes,toensurethebookisafirst-class
citizenthat’suptotheprofessionalstandardsyou’dexpect.
Ifyou’dliketostartyourjourneyintographicsprogrammingyou’vegotagreatpathahead
ofyou. Thisbookwillteachyou,stepbystep,thefoundationandskillsofbecomingagraphics
programmer.You’lllearn3Dfundamentals,basicandadvancedlighting,modelloading,blending,
post-processing,shadows,debugging,PBR,andsomuchmore;andwe’llevenwalkyouthrough
theprocessofcreatingafull2Dgame.Ifyou’reasexcitedasIamIwillnowstoptalkingandsee
youinthefirstchapter.
//Joey
1. Introduction
Sinceyoucamehereyouprobablywanttolearntheinnerworkingsofcomputergraphicsanddoall
thestuffthecoolkidsdobyyourself.Doingthingsbyyourselfisextremelyfunandresourcefuland
givesyouagreatunderstandingofgraphicsprogramming.However,thereareafewitemsthatneed
tobetakenintoconsiderationbeforestartingyourjourney.
1.1 Prerequisites
SinceOpenGLisagraphicsAPIandnotaplatformofitsown,itrequiresalanguagetooperate
inandthelanguageofchoiceisC++. ThereforeadecentknowledgeoftheC++programming
languageisrequiredforthesetutorials. However,Iwilltrytoexplainmostoftheconceptsused,
includingadvancedC++topicswhererequiredsoitisnotrequiredtobeanexpertinC++,but
youshouldbeabletowritemorethanjusta’Hello World’program.Ifyoudon’thavemuch
experiencewithC++Icanrecommendthefreetutorialsatwww.learncpp.com.
Also, we will be using some math (linear algebra, geometry, and trigonometry) along the
wayandIwilltrytoexplainalltherequiredconceptsofthemathrequired. However,I’mnota
mathematicianbyheartsoeventhoughmyexplanationsmaybeeasytounderstand,theywillmost
likelybeincomplete.SowherenecessaryIwillprovidepointerstogoodresourcesthatexplainthe
materialinamorecompletefashion.Don’tbescaredaboutthemathematicalknowledgerequired
beforestartingyourjourneyintoOpenGL;almostalltheconceptscanbeunderstoodwithabasic
mathematicalbackgroundandIwilltrytokeepthemathematicstoaminimumwherepossible.
Mostofthefunctionalitydoesn’tevenrequireyoutounderstandallthemathaslongasyouknow
howtouseit.
1.2 Structure
LearnOpenGLisbrokendownintoanumberofgeneralsections. Eachsectioncontainsseveral
chaptersthateachexplaindifferentconceptsinlargedetail. Thesubjectsaretaughtinalinear
fashion(soitisadvisedtostartfromstarttofinish,unlessotherwiseinstructed)whereeachchapter
explainsthebackgroundtheoryandthepracticalaspects.
Tomaketheconceptseasiertofollow,andgivethemsomeaddedstructure,thebookcontains
boxes,codeblocks,andcolorhints.
1.2.1 Boxes
Greenboxesencompassessomenotesorusefulfeatures/hintsaboutOpenGLorthe
subjectathand.
Redboxeswillcontainwarningsorotherfeaturesyouhavetobeextracarefulwith.
1.2.2 Code
Youwillfindplentyofsmallpiecesofcodeinthebookthatarelocatedindark-grayboxeswith
syntax-highlightedcodeasyoucanseebelow:
// This box contains code
Sincetheseprovideonlysnippetsofcode,wherevernecessaryyou’llfindapathtothefullsource
codeofthechapterdemo(s). ThesourcecodepathsarerelativetotherootoftheLearnOpenGL
repositoryonGitHubwhichyoucanfindat: github.com/JoeyDeVries/learnopengl.
Therepositorycontainsfullsourcecodesamplesforeverychapter.It’srecommendedtodownload
8 Chapter1.Introduction
the repository and review the full source code samples at the end of each chapter to see how
everythingfitstogetherasawhole.
1.2.3 Colorhints
Somewordsaredisplayedwithadifferentcolortomakeitextraclearthesewordsportrayaspecial
meaning:
• Definition: greenwordsspecifyadefinitioni.e. animportantaspect/nameofsomething
you’relikelytohearmoreoften.
• Program structure:redwordsspecifyfunctionnamesorclassnames.
• Variables:bluewordsspecifyvariablesincludingallOpenGLconstants.
Nowthatyougotabitofafeelofthestructureofthebook,hopovertotheGettingStarted
sectiontostartyourjourneyinOpenGL!
I
Getting started
2 OpenGL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Creating a window . . . . . . . . . . . . . . . . . . . . . 14
4 Hello Window . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5 Hello Triangle . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6 Shaders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
7 Textures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
8 Transformations . . . . . . . . . . . . . . . . . . . . . . . . 67
9 Coordinate Systems . . . . . . . . . . . . . . . . . . . . 82
10 Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
11 Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
2. OpenGL
BeforestartingourjourneyweshouldfirstdefinewhatOpenGLactuallyis. OpenGLismainly
consideredanAPI(anApplicationProgrammingInterface)thatprovidesuswithalargesetof
functionsthatwecanusetomanipulategraphicsandimages.However,OpenGLbyitselfisnotan
API,butmerelyaspecification,developedandmaintainedbythewww.khronos.org/.
TheOpenGLspecificationspecifiesexactlywhattheresult/outputofeachfunctionshouldbe
andhowitshouldperform.Itisthenuptothedevelopersimplementingthisspecificationtocomeup
withasolutionofhowthisfunctionshouldoperate.SincetheOpenGLspecificationdoesnotgive
usimplementationdetails,theactualdevelopedversionsofOpenGLareallowedtohavedifferent
implementations,aslongastheirresultscomplywiththespecification(andarethusthesametothe
user).
ThepeopledevelopingtheactualOpenGLlibrariesareusuallythegraphicscardmanufacturers.
EachgraphicscardthatyoubuysupportsspecificversionsofOpenGLwhicharetheversionsof
OpenGLdevelopedspecificallyforthatcard(series). WhenusinganApplesystemtheOpenGL
libraryismaintainedbyApplethemselvesandunderLinuxthereexistsacombinationofgraphic
suppliers’versionsandhobbyists’adaptationsoftheselibraries. Thisalsomeansthatwhenever
OpenGLisshowingweirdbehaviorthatitshouldn’t,thisismostlikelythefaultofthegraphics
cardsmanufacturers(orwhoeverdeveloped/maintainedthelibrary).
Sincemostimplementationsarebuiltbygraphicscardmanufacturers.Wheneverthereis
abugintheimplementationthisisusuallysolvedbyupdatingyourvideocarddrivers;
thosedriversincludethenewestversionsofOpenGLthatyourcardsupports.Thisisone
ofthereasonswhyit’salwaysadvisedtooccasionallyupdateyourgraphicdrivers.
KhronospubliclyhostsallspecificationdocumentsforalltheOpenGLversions.Theinterested
readercanfindtheOpenGLspecification1ofversion3.3(whichiswhatwe’llbeusing),whichis
agoodreadifyouwanttodelveintothedetailsofOpenGL(notehowtheymostlyjustdescribe
resultsandnotimplementations).Thespecificationsalsoprovideagreatreferenceforfindingthe
exactworkingsofitsfunctions.
2.1 Core-profile vs Immediate mode
In the old days, using OpenGL meant developing in immediate mode (often referred to as the
fixed function pipeline) which was an easy-to-use method for drawing graphics. Most of the
functionalityofOpenGLwashiddeninsidethelibraryanddevelopersdidnothavemuchcontrol
overhowOpenGLdoesitscalculations.Developerseventuallygothungryformoreflexibilityand
overtimethespecificationsbecamemoreflexibleasaresult;developersgainedmorecontrolover
theirgraphics. Theimmediatemodeisreallyeasytouseandunderstand,butitisalsoextremely
inefficient.Forthatreasonthespecificationstartedtodeprecateimmediatemodefunctionalityfrom
version3.2onwardsandstartedmotivatingdeveloperstodevelopinOpenGL’score-profilemode,
whichisadivisionofOpenGL’sspecificationthatremovedallolddeprecatedfunctionality.
WhenusingOpenGL’score-profile,OpenGLforcesustousemodernpractices.Wheneverwe
trytouseoneofOpenGL’sdeprecatedfunctions,OpenGLraisesanerrorandstopsdrawing.The
1www.opengl.org/registry/doc/glspec33.core.20100311.withchanges.pdf