HijackGL--Non-Invasive Extensibility for Graphics Applications
Alex Mohr, Michael Gleicher and Christopher Herrman
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Non-Invasive, Interactive, Stylized Rendering
Reconstructing From Streams for Stylized Rendering
HijackGL is a system in development by Alex Mohr and Christopher Herrman
under the direction of Michael Gleicher at the University of Wisconsin.
The goal of this work is to develop a system that allows us to explore
what can be done by intercepting, interpreting, and transforming the
calls an application makes to the OpenGL graphics library. Preliminary
work on this system led to research
presented at the 2001 Interactive 3D Graphics Symposium. This work
focused on generating non-photorealistic renderers for existing
applications. For example, we demonstrated a pencil-sketch-style
renderer running on id Software's Quake III Arena, as shown at the top
of this page. We did not modify the source code of Quake III Arena at
all. In fact, we do not even have access to the Quake III Arena source
code. Current work involves developing a more general system to allow
us to experiment with other kinds of non-invasive extensions.
Here we show our pencil-sketch plug-in renderer. On the left is a scene
from Quake III Arena, and on the right is an image from the Atlantis
Here are screenshots of Maya viewing the geometry of level q3dm17,
captured by our 3D-Screenshot system plug-in, and also the geometry of
the Atlantis program, captured the same way.
We have decided to make some binaries available for download. BE
WARNED! These are very rough and not well tested. It is
likely they will not work for you, but they might.
Place these files in the directory that you run your program
opengl32.dll -- Intercepting OpenGL library (do NOT replace your system library with this!)
pencilsketch.glr -- Pencil-sketch plugin.
screencap.glr -- 3D geometry capture plugin.
blueprint.glr -- Blueprint rendering plugin.
toon.glr -- Cartoon rendering plugin.
pencil.tga -- Texture map used by pencil-sketch plugin.
These files do not need to be moved:
README.txt -- Instructions for use.
atlantis.exe -- Simple OpenGL test program.
glsample.exe -- Another simple test program.
After you've extracted the package to some directory, try running the
atlantis program, and see if a dialog box pops up. If it does, select
the pencilsketch.glr file. Now the atlantis program should start, and
you should see some sea creatures swimming on a field of blue. To turn
on the pencil-sketch version, simply press the SCROLL LOCK key. The
background should turn gray, and the sea creatures should look
"sketchy". To turn off the pencil-sketch renderer, press SCROLL LOCK
To make pencilsketch work with Quake 3, it takes some work. First, run
Quake 3 WITHOUT having the HijackGL stuff in the directory. That is,
run it normally. Make sure you have Quake 3 set up to run in
NON-FULLSCREEN mode. If it is in fullscreen mode, you will not be able
to get at the dialog box to select a renderer. Also, go into game
options and turn off "high quality sky". At the console, type the
command /cg_draw2D 0, to turn off drawing UI elements. You may also
want to turn off drawing the first-person gun with /cg_drawGun 0 to get
a better view of the screen.
Now, go ahead and copy the HijackGL binaries to the Quake 3 directory
and run the program. Things should look normal. Start up a game like
normal. When the map comes up and you are running around, try pressing
SCROLL LOCK to turn on the renderer. It should work. Pressing SCROLL
LOCK again will turn off the renderer. If your colors seem to be wrong,
after it's turned off, try pulling down the console.
If it doesn't work for you, there's nothing much we can do. Certainly
don't bother id Software about it -- they are not affiliated with us.
Also, you will probably notice a big speed hit, and some people might
consider it cheating if you use this in online play.
Operation of the screencap plugin: Pressing SCROLL LOCK while using the
screencap plugin will take a "3D screenshot" of the scene's geometry and
write it to a file called "screencap.obj" in the program's directory.
This is a standard Wavefront OBJ file that can be viewed with a program
like Maya. If you notice bits of geometry missing from scenes taken
from Quake 3, this is normal. Quake 3 does very aggressive visibility
culling, so much of what you cannot see does not show up.
We are not releasing source code at this time for a couple of reasons.
First, the system is being reengineered, so the code is changing very
quickly. Second, this system can be used to cheat at online games --
it's very easy to write a plugin that makes walls translucent, for
instance. We don't want to encourage that at all. We all know what the
ASUS drivers did.