Jason Mitchell spent 8 years
working for ATI, where he headed up the 3D Application
Research Group. He is now utilizing his 3D graphics
hardware wizardry on new projects at Valve. Gabe
Newell who is the Founder and Managing
Director of Valve, made several poignant points
during the presentation. Doug Lombardi,
Director of Marketing also made appropriate references
and helped bring the whole gathering together with
the help of able assistant Ms. Kathy Gehrig.
Now that we’ve given
you a little bit of background on our presenters
– let’s find out what all the hoopla
was about.
Valve wanted to take what
they learned from developing Lost
Coast to the technology folks who
worked diligently on Day of Defeat: Source. The
DOD trailer was made in order to show filmic effects
in the Source Engine, such as the HDR lightning
initially presented in Lost Coast, along with other
technologies which are being added incrementally.
The DOD film that Valve made will be used to show
off these post processing results.
Valve’s Jason Mitchell
made a comment at the beginning of the presentation
stating “We are applying complexity that isn’t
really there”. By using the aforementioned
filmic effects, it gave the trailer a World
War II newsreel type look. Video games have
focused on explicit complexity in order to increase
realism in games. This was discussed as an area
of perception for those growing up with still and
motion photography.
In the DOD trailer, standard
models, textures and physics were used. The animation
was player driven. Much of the realism in this trailer
comes from the filmic effects that Valve has developed.
The trailer was constructed piece by piece.
Some of the initial goals
were to increase realism by implying complexity,
and to use filmic effects over existing game assets.
By using the considerable assets that Valve already
has, they can get the most out of the content they
have already produced.
The non real-time effects
that Valve implemented were Motion Blur and Depth
of Field, and these are being used in order to steer
future hardware requirements and needs. The real-time
effects include Color Correction, and the use of
Film Grain and
Dust. To paraphrase what was discussed
at the Hardware Editor’s Day at Valve –
Video games have historically focused on explicit
complexity, i.e. polygonal and texture complexities,
while ignoring non three dimensional solutions.
Film grain, depth of field, and motion blur do indeed
reduce the actual “fidelity” of the
image, but perceptually, the scene becomes more
complex due to the visual cueing.
With Valve creating the
Day of Defeat trailer, they were able to use all
in game assets, such as the standard shipping shaders,
textures, models, physics, and player driven animation.
The trailer was made “on location” in
the game Day of Defeat. How did Valve do it? The
realistic and stylized looks of this piece come
from the filmic post processing, by using motion
blur, depth of field, color correction and film
grain effects. One of their stated goals was to
render images over some finite duration of time,
instead of the way games currently typically render
images representing the state of the world, at infinitesimal
instances in time.
Please click here
to view the DOD movie trailer as produced by Valve
- converted to DIVX/XVID
(please
note this file is almost 60 megabytes, if you are
having troubles streaming, right click save as)
Below is
an image without any effects.
No Effects |
Motion blur in films and
games, present a virtual sequence of images to the
end user at a fixed frame rate. Typically, these
values are 24Hz for film, and 29.97Hz for video.
According to Valve’s slide presentation, real
or virtual film is exposed to the continuously moving
world during that finite period of time, approximately
1/24th of a second, etc. This is because elements
of a scene which are in motion (this includes the
camera and viewer) become blurred due to their motion
across the image during exposure. What Valve has
discovered is this technique brings a surprising
amount of “weight” to the particular
scene, thus causing the viewer to then perceive
more complexity. In other words by using this particular
technique of motion blur, think of this as antialiasing
in time, rather than in space. Jason Mitchell from
Valve stated “The camera itself can be in
motion and causes certain characteristics of blurring
in the image itself.” Of course discerning
readers will note that anti-aliasing has been a
hot topic the past few years, being shown discrete
images in time.
Below please note the example
picture, with no effects except for motion blur
noted on the right split screen.
No Depth of Field or Motion
Blur //// Motion Blur |
Next, we will move onto
a brief discussion of Depth of Field. This is the
use of focal distance and developing techniques
to bring the language of cinema to the games. You
can think of focal distance as another information
substance in game play. Physical cameras inherently
have a focal distance, meaning that points in the
scene which are nearer or farther than this distance
become increasingly blurry. Depth of Field is used
to dramatic effect in still photography as well
as in the motion picture field. This can draw the
user’s attention to specific scene elements.
Computer generated graphics typically use a pinhole
camera model which produces in-focus images everywhere.
Let’s examine a few
more frame captures to see how Depth of Field plays
a significant role in game development of the future.
no Depth of Field or Motion Blur |
The image above again depicts
no Depth of Field or Motion Blur – next we
will look at a still screen capture shot which shows
the blurring in the distance below.
blur in the distance |
The next image below shows
a viewpoint from the camera strafing left, with
the soldiers in motion. This particular screen capture
used Motion Blur effects only.
Note the shadows under the characters as they move.
Motion Blur effects only |
Here is another shot with
no Depth of Field or Motion Blur below.
no Depth of Field or Motion Blur |
Next we move on to a picture
showing Depth of Field only, located below. Note
how your eyes are drawn to the sharp balcony.
Depth of Field |
The next image is the same
shot, only it is using Motion Blur effects only.
The balcony is not as sharp nor does it draw focus
like using Depth of Field did.
Motion Blur effects only |
Below please find a shot
of using both Depth of Field and Motion Blur combined
to see those results.
Depth of Field and Motion Blur |
The image below shows no
Depth of Field, with Motion Blur effects included
below.
no Depth of Field, with Motion Blur effects |
A single split screen windowed
view shows no effects of Depth of Field or Motion
Blur on the left side of the image below, while
Depth of Field and Motion Blur is turned on in the
right side of the image.
mixed image (read above) |
The following are download
links, containing 25 seconds of the DOD trailer
that Valve made.
dod_tech_01_none
- This is the first clip with no effects
at all
The next clip is a split
screened movie, with no effects on the left side,
and Depth of Field has been invoked on right side
of screen.
dodt_tech_02_split_dof_b
The next following link below
shows the same 25 second clip, split screened, with
no effects on the left side and Motion Blur on in
the right side of screen.
dodt_tech_03_split_mblur_b
In the next 25 second clip
of the same DOD trailer, notice that the screen
is split again, and this time both Depth of Field
and Motion Blur are turned on below.
dodt_tech_04_split_both_b
Finally our last clip of
the same length shows both Depth of Field and Motion
Blur turned on with the full screen displayed.
dodt_tech_05_both
