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The image is autogenerated with the below description using the command dot from the Graphviz package.

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// dot -oengine.svg -Tsvg engine.dot
digraph {
	ratio=auto;
	sep="+4,5";

	// =============================
	// Engines
	// =============================
	node [shape=polygon, sides=6, style=filled]

	// id Tech engines
	node [peripheries=4, size=6]
    fontsize=20
	// id Tech engines under GPL
	node [fillcolor=lightgreen]
    //Quake
	QuakeE [label="Quake engine"]
	GLQuake
	WinQuake
	QuakeWorld

	Quake2E [label="Quake II engine"]
	idTech3 [label="id Tech 3\nQuake III Arena engine"]
	idTech4 [label="id Tech 4\nDoom 3 engine"]

	// id Tech under commercial license
	node [fillcolor=lightgrey]
	idTech5 [label="id Tech 5"]
    idTech6 [label="id Tech 6"]
    idTech7 [label="id Tech 7"]
    idTech8 [label="id Tech 8"]

	// Other engines
	//
	node [peripheries=1]

	// Other commercial engines
	node [fillcolor=lightgrey]
	GoldSrc
	SourceEngine [label="Source Engine"]
    Source2 [label="Source 2"]
	
	Void [label="Void Engine"] //Forked from id Tech 5, for Dishonored 2
	Motor //Forked from id Tech 7, for Indiana Jones and the Great Circle

	// Other libre/open engines
	node [fillcolor=lightgreen]
	DarkPlaces

	// =============================
	// Games
	// =============================
	node [shape=ellipse, color=transparent]

	// Commercial Games
	node [fillcolor=lightgrey]
	// id and Bethesda
	Quake
	HexenII [label="Hexen II"]

	QuakeII [label="Quake II"]

	QuakeIIIArena [label="Quake III Arena"]
	QuakeLive [label="Quake Live"]

	Doom3 [label="Doom 3"]
	Quake4 [label="Quake 4"]

	Rage
	WolfensteinTNO [label="Wolfenstein: The New Order"]
	WolfensteinTBO [label="Wolfenstein: The Old Blood"]
	
	Dishonored2 [label="Dishonored 2"]
	Deathloop

	Doom2016 [label="DOOM (2016)"]
	Wolfenstein2 [label="Wolfenstein II: The New Colossus"]
	WolfensteinYB [label="Wolfenstein: Youngblood"]

	DoomEternal [label="Doom Eternal"]
	
	TheGreatCircle [label="Indiana Jones and the Great Circle"]
	
	DoomDarkAges [label="Doom: The Dark Ages"]

	// GoldSrc & Source
	HalfLife [label="Half-Life"]
	TFC [label="Team Fortress Classic"]
	CS [label="Counter-Strike"]
	DoD [label="Day of Defeat"]

	Halflife2  [label="Half-Life 2"]
	DoDS [label="Day of Defeat: Source"]
	gmod [label="Garry's Mod"]
	l4d [label="Left 4 Dead"]
	portal [label="Portal"]
	portal2 [label="Portal 2"]
	HLA [label="Half-Life: Alyx"]

	Titanfall
	titanfall2 [label="Titanfall 2"]
	
	COD [label="Call of Duty"]
	
	// Freeware games
	node [fillcolor=lightblue]
	TF2 [label="Team Fortress 2"]
	csgo [label="Counter-Strike: Global Offensive"]
	cs2 [label="Counter-Strike 2"]
	dota2 [label="Dota 2"]
	Deadlock
	apex [label="Apex Legends"]

	// Libre/open games
	node [fillcolor=lightgreen]

	// =============================
	// Trees
	// =============================

	QuakeE -> Quake2E -> idTech3 -> idTech4 -> idTech5 -> idTech6 -> idTech7 -> idTech8

    QuakeE -> {WinQuake,GLQuake,QuakeWorld,DarkPlaces}
	QuakeE -> {Quake,HexenII}
    {QuakeWorld,GLQuake,WinQuake} -> Quake
	Quake2E -> QuakeII
	idTech3 -> {QuakeIIIArena, COD, QuakeLive}
	idTech4 -> {Doom3, Quake4}
	idTech5 -> {Rage,WolfensteinTNO,WolfensteinTBO,Void}
	Void -> {Dishonored2,Deathloop}
	idTech6 -> {Doom2016,Wolfenstein2,WolfensteinYB}
	idTech7 -> {DoomEternal,Motor}
	Motor -> TheGreatCircle
	idTech8 -> DoomDarkAges

    GoldSrc -> SourceEngine -> Source2
    {QuakeWorld,Quake2E,QuakeE} -> GoldSrc
	GoldSrc -> {HalfLife,TFC}
	HalfLife -> {DoD,CS}

	SourceEngine -> {Halflife2,DoDS,TF2,l4d,portal,csgo,dota2,Titanfall,gmod}
	portal -> portal2

	Source2 -> {dota2,HLA,cs2,Deadlock}

	Titanfall -> titanfall2 -> apex
}
}

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