<s>
Build	B-Application
Engine	I-Application
is	O
a	O
first-person	O
shooter	O
engine	O
created	O
by	O
Ken	O
Silverman	O
,	O
author	O
of	O
Ken	B-Application
's	I-Application
Labyrinth	I-Application
,	O
for	O
3D	O
Realms	O
.	O
</s>
<s>
Like	O
the	O
Doom	B-Application
engine	I-Application
,	O
the	O
Build	B-Application
Engine	I-Application
represents	O
its	O
world	O
on	O
a	O
two-dimensional	O
grid	O
using	O
closed	O
2D	O
shapes	O
called	O
sectors	O
,	O
and	O
uses	O
simple	O
flat	O
objects	O
called	O
sprites	O
to	O
populate	O
the	O
world	O
geometry	O
with	O
objects	O
.	O
</s>
<s>
The	O
Build	B-Application
Engine	I-Application
is	O
generally	O
considered	O
to	O
be	O
a	O
2.5D	O
engine	O
since	O
the	O
basic	O
world	O
geometry	O
is	O
two-dimensional	O
with	O
an	O
added	O
height	O
component	O
,	O
allowing	O
each	O
sector	O
to	O
have	O
a	O
different	O
ceiling	O
height	O
and	O
floor	O
height	O
.	O
</s>
<s>
With	O
this	O
information	O
,	O
the	O
Build	B-Application
Engine	I-Application
renders	O
the	O
world	O
in	O
a	O
way	O
that	O
looks	O
three-dimensional	O
,	O
unlike	O
modern	O
game	O
engines	O
that	O
create	O
actual	O
3D	O
environments	O
.	O
</s>
<s>
Though	O
the	O
Build	B-Application
Engine	I-Application
achieved	O
most	O
of	O
its	O
fame	O
as	O
a	O
result	O
of	O
powering	O
the	O
1996	B-Application
first-person	O
shooter	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
,	O
it	O
was	O
also	O
used	O
for	O
many	O
other	O
games	O
.	O
</s>
<s>
Sectors	O
are	O
the	O
building	O
blocks	O
of	O
a	O
level	O
's	O
layout	O
,	O
consisting	O
of	O
a	O
two-dimensional	O
polygonal	O
outline	O
when	O
viewed	O
from	O
above	O
,	O
with	O
the	O
top	O
and	O
bottom	O
faces	O
of	O
the	O
sector	O
given	O
separate	O
altitudes	B-Application
to	O
create	O
a	O
three-dimensional	O
space	O
.	O
</s>
<s>
Sectors	O
can	O
be	O
manipulated	O
in	O
real-time	O
;	O
all	O
of	O
their	O
attributes	O
such	O
as	O
shape	O
,	O
height	O
,	O
and	O
slope	O
could	O
be	O
modified	O
"	O
on-the-fly	O
"	O
by	O
games	O
,	O
unlike	O
the	O
earlier	O
Doom	B-Application
engine	I-Application
.	O
</s>
<s>
This	O
allowed	O
games	O
to	O
have	O
destructible	O
environments	O
,	O
such	O
as	O
those	O
seen	O
in	O
Blood	B-Application
.	O
</s>
<s>
This	O
technique	O
is	O
similar	O
to	O
the	O
use	O
of	O
push	O
walls	O
in	O
the	O
earlier	O
Apogee	O
Software	O
title	O
Rise	B-Application
of	I-Application
the	I-Application
Triad	I-Application
which	O
featured	O
similar	O
dynamic	O
environments	O
.	O
</s>
<s>
While	O
all	O
these	O
made	O
the	O
games	O
using	O
the	O
engine	O
appear	O
to	O
be	O
3D	O
,	O
it	O
would	O
n't	O
be	O
until	O
later	O
first-person	O
shooters	O
,	O
such	O
as	O
Quake	B-Application
,	O
which	O
used	O
the	O
Quake	B-Application
engine	I-Application
,	O
that	O
the	O
engine	O
actually	O
stored	O
the	O
world	O
geometry	O
as	O
true	O
3D	O
information	O
,	O
making	O
the	O
creation	O
of	O
one	O
area	O
stacked	O
atop	O
another	O
area	O
in	O
a	O
single	O
map	O
very	O
feasible	O
.	O
</s>
<s>
Later	O
versions	O
of	O
Ken	O
Silverman	O
's	O
Build	B-Application
Engine	I-Application
allowed	O
game	O
selected	O
art	O
tiles	O
to	O
be	O
replaced	O
by	O
3D	O
objects	O
made	O
of	O
voxels	B-Algorithm
.	O
</s>
<s>
This	O
feature	O
appeared	O
too	O
late	O
to	O
be	O
used	O
in	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
,	O
but	O
was	O
seen	O
in	O
some	O
of	O
the	O
later	O
Build	B-Application
Engine	I-Application
games	O
.	O
</s>
<s>
Blood	B-Application
uses	O
voxels	B-Algorithm
for	O
weapon	O
and	O
ammo	O
pickups	O
,	O
power-ups	O
,	O
and	O
eye-candy	O
(	O
such	O
as	O
the	O
tombstones	O
in	O
the	O
"	O
Cradle	O
to	O
Grave	O
"	O
level	O
,	O
some	O
chairs	O
,	O
and	O
a	O
crystal	O
ball	O
in	O
"	O
Dark	O
Carnival	O
"	O
)	O
.	O
</s>
<s>
Shadow	B-Application
Warrior	I-Application
makes	O
even	O
more	O
advanced	O
use	O
of	O
the	O
technology	O
,	O
with	O
voxels	B-Algorithm
that	O
can	O
be	O
placed	O
on	O
walls	O
(	O
all	O
of	O
the	O
game	O
's	O
switches	O
and	O
buttons	O
are	O
voxels	B-Algorithm
)	O
.	O
</s>
<s>
For	O
several	O
years	O
,	O
Ken	O
worked	O
on	O
a	O
modern	O
engine	O
based	O
entirely	O
on	O
voxels	B-Algorithm
,	O
known	O
as	O
Voxlap	O
.	O
</s>
<s>
One	O
limitation	O
of	O
the	O
Build	B-Application
Engine	I-Application
is	O
that	O
its	O
level	O
geometry	O
is	O
only	O
capable	O
of	O
representing	O
one	O
connection	O
between	O
sectors	O
for	O
any	O
given	O
wall	O
.	O
</s>
<s>
Due	O
to	O
this	O
,	O
a	O
structure	O
as	O
simple	O
as	O
a	O
shelf	O
with	O
space	O
both	O
above	O
and	O
below	O
it	O
is	O
impossible	O
,	O
though	O
sometimes	O
sprites	O
or	O
voxels	B-Algorithm
can	O
be	O
substituted	O
.	O
</s>
<s>
Several	O
Build	B-Application
Engine	I-Application
games	O
(	O
namely	O
Shadow	B-Application
Warrior	I-Application
,	O
Blood	B-Application
,	O
and	O
Redneck	B-Application
Rampage	I-Application
)	O
worked	O
around	O
this	O
by	O
displaying	O
a	O
"	O
viewport	O
"	O
to	O
another	O
sector	O
through	O
an	O
additional	O
rendering	O
pass	O
.	O
</s>
<s>
ROR	O
was	O
never	O
a	O
feature	O
of	O
the	O
Build	B-Application
Engine	I-Application
itself	O
,	O
but	O
rather	O
a	O
"	O
trick	O
"	O
that	O
was	O
created	O
by	O
game	O
developers	O
.	O
</s>
<s>
A	O
trick	O
used	O
in	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
to	O
get	O
around	O
this	O
,	O
as	O
in	O
the	O
case	O
of	O
its	O
opaque	O
underwater	O
sections	O
,	O
was	O
to	O
simply	O
transport	O
the	O
player	O
quickly	O
to	O
another	O
region	O
of	O
the	O
map	O
made	O
to	O
mimic	O
it	O
,	O
similar	O
to	O
the	O
elevators	O
from	O
Rise	B-Application
of	I-Application
the	I-Application
Triad	I-Application
.	O
</s>
<s>
In	O
2011	O
,	O
a	O
feature	O
was	O
added	O
to	O
EDuke32	B-Application
called	O
true	O
room	O
over	O
room	O
(	O
TROR	O
)	O
,	O
which	O
allows	O
multiple	O
sectors	O
to	O
be	O
stacked	O
vertically	O
so	O
that	O
each	O
sector	O
's	O
wall	O
has	O
its	O
own	O
connection	O
,	O
enabling	O
vertically-unrestricted	O
structures	O
.	O
</s>
<s>
TROR	O
is	O
a	O
feature	O
of	O
the	O
EDuke32	B-Application
source	O
port	O
,	O
not	O
a	O
game	O
feature	O
or	O
trick	O
.	O
</s>
<s>
YearTitleDeveloperNotes1994Rock'n	O
Shaolin	O
:	O
Legend	O
of	O
Seven	O
Paladins	O
3DAccend	O
Inc.Illegally	O
used	O
an	O
earlier	O
version	O
of	O
the	O
engine	O
,	O
only	O
released	O
in	O
Taiwan	O
and	O
South	O
Korea.1995WitchavenCapstone	O
SoftwareWilliam	O
Shatner	O
's	O
TekWar1996Duke	O
Nukem	O
3D3D	O
RealmsAlso	O
Plutonium	O
PAK	O
,	O
Atomic	O
Edition	O
,	O
Duke	O
!	O
ZONE	O
II	O
,	O
Xtreme	O
,	O
Duke	O
it	O
Out	O
in	O
D.C.	O
,	O
Life	O
's	O
a	O
Beach	O
and	O
Nuclear	O
Winter	O
expansions.PowerSlaveLobotomy	O
SoftwareWitchaven	O
II	O
:	O
Blood	B-Application
VengeanceCapstone	O
Software1997BloodMonolith	O
ProductionsAlso	O
Plasma	O
Pak	O
and	O
Cryptic	O
Passage	O
expansions.Shadow	O
Warrior3D	O
RealmsAlso	O
Twin	O
Dragon	O
and	O
Wanton	O
Destruction	O
expansions	O
.	O
</s>
<s>
The	O
Build	B-Application
Engine	I-Application
was	O
essentially	O
a	O
one-man	O
project	O
for	O
Ken	O
Silverman	O
,	O
though	O
he	O
consulted	O
John	O
Carmack	O
for	O
guidance	O
early	O
in	O
the	O
project	O
.	O
</s>
<s>
On	O
June	O
20	O
,	O
2000	O
(	O
according	O
to	O
his	O
website	O
)	O
Ken	O
Silverman	O
released	O
the	O
Build	B-Application
Engine	I-Application
source	O
code	O
under	O
a	O
proprietary	O
non-commercial	O
license	O
.	O
</s>
<s>
Silverman	O
explained	O
that	O
after	O
id	O
Software	O
set	O
a	O
precedent	O
by	O
releasing	O
the	O
source	O
code	O
for	O
the	O
Doom	B-Application
engine	I-Application
,	O
fans	O
had	O
been	O
pressuring	O
him	O
to	O
release	O
the	O
source	O
code	O
for	O
the	O
Build	B-Application
Engine	I-Application
.	O
</s>
<s>
Version	O
2.0	O
of	O
Matt	O
Saettler	O
's	O
EDuke	O
,	O
a	O
project	O
to	O
improve	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
for	O
modders	B-Device
,	O
was	O
sent	O
to	O
3D	O
Realms	O
for	O
packaging	O
shortly	O
after	O
the	O
release	O
of	O
the	O
Build	O
source	O
,	O
leaving	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
the	O
pre-built	O
libraries	O
that	O
3D	O
Realms	O
had	O
used	O
with	O
the	O
original	O
Duke	O
.	O
</s>
<s>
(	O
Both	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
and	O
EDuke	O
were	O
still	O
closed-source	O
at	O
this	O
point	O
.	O
)	O
</s>
<s>
This	O
statement	O
did	O
not	O
hold	O
up	O
to	O
scrutiny	O
,	O
as	O
all	O
modern	O
operating	O
systems	O
use	O
virtual	B-Architecture
memory	I-Architecture
which	O
allows	O
apps	O
to	O
get	O
contiguous	O
logical	O
memory	O
without	O
using	O
contiguous	O
physical	O
memory	O
,	O
but	O
conventional	O
wisdom	O
of	O
the	O
time	O
was	O
that	O
porting	O
Build	O
to	O
such	O
an	O
OS	O
was	O
unfeasible	O
.	O
</s>
<s>
On	O
April	O
1	O
,	O
2003	O
,	O
after	O
several	O
years	O
of	O
claims	O
to	O
the	O
contrary	O
,	O
3D	O
Realms	O
released	O
the	O
source	O
code	O
to	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
under	O
the	O
GPL-2.0-or-later	B-License
license	O
.	O
</s>
<s>
Not	O
long	O
afterwards	O
,	O
both	O
Ryan	O
C	O
.	O
Gordon	O
and	O
Jonathon	O
Fowler	O
created	O
and	O
released	O
source	O
ports	O
of	O
the	O
game	O
,	O
including	O
the	O
Build	B-Application
Engine	I-Application
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
play	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
well	O
on	O
the	O
NT	O
line	O
of	O
Windows	O
(	O
including	O
Windows	O
2000/XP	O
)	O
and	O
on	O
Linux	B-Application
and	O
other	O
Unix	B-Application
operating	I-Application
systems	I-Application
,	O
and	O
interest	O
in	O
the	O
source	O
ports	O
soared	O
.	O
</s>
<s>
Ryan	O
C	O
.	O
Gordon	O
(	O
icculus	O
)	O
,	O
with	O
the	O
help	O
of	O
others	O
,	O
made	O
the	O
first	O
port	O
of	O
the	O
engine	O
using	O
SDL	B-Operating_System
.	O
</s>
<s>
The	O
port	O
was	O
first	O
to	O
Linux	B-Application
,	O
then	O
to	O
Cygwin	B-Language
,	O
and	O
finally	O
to	O
a	O
native	O
Windows	O
build	O
using	O
the	O
Watcom	B-Application
C++	I-Application
compiler	O
,	O
which	O
was	O
the	O
compiler	O
used	O
for	O
the	O
original	O
DOS	O
build	O
(	O
despite	O
being	O
compiled	O
with	O
Watcom	B-Application
C++	I-Application
,	O
Build	O
is	O
plain	O
C	O
.	O
)	O
There	O
was	O
some	O
talk	O
of	O
Matt	O
Saettler	O
using	O
this	O
to	O
port	O
EDuke	O
to	O
Windows	O
,	O
but	O
nothing	O
came	O
of	O
it	O
.	O
</s>
<s>
A	O
second	O
source	O
port	O
was	O
made	O
to	O
Windows	O
,	O
and	O
later	O
to	O
Linux	B-Application
and	O
Mac	O
OS	O
X	O
,	O
by	O
Jonathon	O
Fowler	O
(	O
JonoF	O
)	O
.	O
</s>
<s>
The	O
task	O
of	O
updating	O
the	O
Build	B-Application
Engine	I-Application
to	O
a	O
true	O
3D	O
renderer	O
was	O
taken	O
on	O
by	O
Silverman	O
himself	O
.	O
</s>
<s>
In	O
the	O
release	O
notes	O
for	O
Polymost	O
,	O
he	O
wrote	O
:	O
"	O
When	O
3D	O
Realms	O
released	O
the	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
source	O
code	O
,	O
I	O
thought	O
somebody	O
would	O
do	O
a	O
OpenGL	B-Application
or	O
Direct3D	O
port	O
.	O
</s>
<s>
The	O
Polymost	O
renderer	O
allowed	O
for	O
3D	O
hardware-accelerated	O
graphics	O
using	O
OpenGL	B-Application
.	O
</s>
<s>
Richard	O
Gobeille	O
(	O
TerminX	O
)	O
merged	O
the	O
EDuke	O
2.0	O
source	O
with	O
JFDuke3D	O
to	O
make	O
EDuke32	B-Application
.	O
</s>
<s>
Another	O
port	O
,	O
Wineduke	O
,	O
based	O
on	O
the	O
icculus	O
code	O
,	O
has	O
since	O
died	O
off	O
,	O
leaving	O
EDuke32	B-Application
the	O
only	O
EDuke	O
port	O
still	O
in	O
development	O
.	O
</s>
<s>
EDuke32	B-Application
also	O
supports	O
the	O
games	O
NAM	B-Application
and	O
WWII	B-Application
GI	I-Application
,	O
as	O
EDuke	O
was	O
based	O
on	O
the	O
code	O
to	O
those	O
games	O
.	O
</s>
<s>
On	O
April	O
1	O
,	O
2009	O
,	O
an	O
OpenGL	B-Application
shader	O
model	O
3.0	O
renderer	O
was	O
revealed	O
to	O
have	O
been	O
developed	O
for	O
EDuke32	B-Application
,	O
named	O
Polymer	O
to	O
distinguish	O
from	O
Ken	O
Silverman	O
's	O
Polymost	O
.	O
</s>
<s>
It	O
allows	O
for	O
more	O
modern	O
effects	O
such	O
as	O
real-time	O
dynamic	O
colored	O
lighting	O
and	O
shadow	O
mapping	O
,	O
specular	O
and	O
normal	B-Application
mapping	I-Application
,	O
and	O
other	O
shader-based	O
features	O
in	O
addition	O
to	O
most	O
of	O
the	O
features	O
added	O
to	O
Polymost	O
over	O
the	O
years	O
.	O
</s>
<s>
The	O
developers	O
of	O
EDuke32	B-Application
have	O
stated	O
that	O
once	O
Polymer	O
has	O
been	O
rewritten	O
for	O
speed	O
,	O
it	O
will	O
supplant	O
Polymost	O
completely	O
,	O
as	O
it	O
is	O
a	O
superior	O
renderer	O
,	O
and	O
can	O
be	O
made	O
to	O
look	O
identical	O
to	O
Polymost	O
.	O
</s>
<s>
The	O
Shadow	B-Application
Warrior	I-Application
source	O
code	O
was	O
released	O
on	O
April	O
1	O
,	O
2005	O
under	O
the	O
GPL-2.0-or-later	B-License
license	O
,	O
and	O
JonoF	O
released	O
a	O
source	O
port	O
of	O
it	O
,	O
JFShadowWarrior	O
,	O
on	O
April	O
2	O
,	O
2005	O
.	O
</s>
<s>
However	O
,	O
he	O
admitted	O
that	O
he	O
had	O
access	O
to	O
the	O
Shadow	B-Application
Warrior	I-Application
source	O
code	O
about	O
a	O
week	O
before	O
its	O
release	O
.	O
</s>
<s>
A	O
VoidSW	O
port	O
by	O
the	O
Ion	B-Application
Fury	I-Application
and	O
EDuke32	B-Application
developers	O
entered	O
public	O
beta	O
on	O
May	O
21	O
,	O
2020	O
.	O
</s>
<s>
The	O
Transfusion	O
project	O
aimed	O
to	O
re-create	O
Blood	B-Application
in	O
the	O
DarkPlaces	B-Application
engine	I-Application
,	O
but	O
as	O
of	O
2007	O
,	O
this	O
project	O
was	O
far	O
from	O
complete	O
,	O
though	O
it	O
has	O
playable	O
deathmatch	O
multiplayer	O
;	O
a	O
similar	O
project	O
is	O
BloodCM	O
which	O
recreates	O
all	O
of	O
the	O
Monolith	O
made	O
single	O
player	O
levels	O
for	O
Blood	B-Application
on	O
top	O
of	O
EDuke32	B-Application
,	O
as	O
well	O
as	O
ZBlood	O
which	O
ports	O
some	O
Blood	B-Application
assets	O
and	O
levels	O
onto	O
ZDoom	O
.	O
</s>
<s>
The	O
eRampage	O
project	O
attempted	O
to	O
create	O
a	O
total	O
conversion	O
of	O
Redneck	B-Application
Rampage	I-Application
for	O
EDuke32	B-Application
.	O
</s>
<s>
The	O
source	O
code	O
of	O
Witchaven	B-Application
,	O
Witchaven	B-Application
II	I-Application
:	I-Application
Blood	I-Application
Vengeance	I-Application
,	O
William	B-Application
Shatner	I-Application
's	I-Application
TekWar	I-Application
,	O
and	O
Corridor	O
8	O
:	O
Galactic	O
Wars	O
have	O
also	O
surfaced	O
.	O
</s>
<s>
The	O
full	O
source	O
code	O
for	O
alpha	O
versions	O
of	O
Blood	B-Application
have	O
also	O
leaked	O
,	O
and	O
was	O
used	O
as	O
a	O
reference	O
for	O
an	O
otherwise	O
reverse	O
engineered	O
port	O
to	O
Java	B-Language
using	O
LibGDX	B-Library
called	O
BloodGDX	O
in	O
May	O
2017	O
by	O
the	O
previous	O
author	O
of	O
BloodCM	O
.	O
</s>
<s>
This	O
followed	O
from	O
the	O
author	O
's	O
previous	O
port	O
of	O
TekWar	B-Application
released	O
in	O
January	O
2016	O
,	O
and	O
has	O
been	O
followed	O
up	O
by	O
ports	O
for	O
Witchaven	B-Application
,	O
Redneck	B-Application
Rampage	I-Application
,	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
,	O
PowerSlave	B-Application
,	O
Legends	O
of	O
the	O
Seven	O
Paladins	O
and	O
Shadow	B-Application
Warrior	I-Application
,	O
now	O
all	O
collectively	O
called	O
BuildGDX	O
.	O
</s>
<s>
DukeGDX	O
also	O
supports	O
the	O
files	O
from	O
the	O
20th	O
Anniversary	O
World	O
Tour	O
edition	O
of	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
.	O
</s>
<s>
A	O
further	O
port	O
of	O
Blood	B-Application
,	O
called	O
NBlood	O
,	O
was	O
released	O
in	O
January	O
2019	O
based	O
on	O
EDuke32	B-Application
,	O
and	O
the	O
creator	O
's	O
previous	O
Rednukem	O
port	O
for	O
Redneck	B-Application
Rampage	I-Application
(	O
which	O
also	O
supports	O
Duke	B-Application
Nukem	I-Application
3D	I-Application
and	O
Duke	B-Application
Nukem	I-Application
64	I-Application
)	O
.	O
</s>
<s>
An	O
EDuke32	B-Application
port	O
for	O
PowerSlave	B-Application
,	O
called	O
PCExhumed	O
,	O
was	O
released	O
on	O
November	O
21	O
,	O
2019	O
.	O
</s>
<s>
The	O
source	O
port	O
Raze	O
forks	O
various	O
Build	B-Application
engine	I-Application
ports	O
,	O
including	O
JFDuke3D	O
,	O
SWP	O
,	O
NBlood	O
,	O
Rednukem	O
,	O
and	O
PCExhumed	O
,	O
and	O
ties	O
it	O
to	O
a	O
new	O
underlying	O
backend	O
based	O
on	O
GZDoom	O
.	O
</s>
<s>
It	O
features	O
a	O
more	O
advanced	O
lighting	O
system	O
,	O
voxel	B-Algorithm
rendering	O
for	O
entities	O
and	O
true	O
room-over-room	O
3D	O
spaces	O
,	O
and	O
at	O
least	O
in	O
part	O
retained	O
backwards	O
compatibility	O
with	O
the	O
original	O
Build	O
.	O
</s>
