 Deinterlacing
Video Textures in Combustion
Using
Video as a Map Source for 3D Texture Models
by Gary M. Davis
3D objects are nothing more than boring surfaces without a texture.
Real-world images and photos are often used as texture maps to add
realism to a 3D scene. Simple diffuse texture maps are the obvious
example, but images can also be used for many effects, including displacement
maps, specular maps and light projections. The raw assets for these
maps can come from any number of sources, such as digital photos,
scanned images or even movie files, such as Jump Backs animated backgrounds
or VideoTraxx stock footage clips.
INTERLACING
Video textures can also be used in very creative, often surreal ways.
Take, for example, the scene pictured in Figure 1. This is an Autodesk
3ds Max scene of a simple primitive teapot wrapped in a piece of VideoTraxx
stock footage. The result is very unusual and attention-getting. It
is also very easy for a 3D artist to map a video onto a 3D object,
but some video-specific problems can crop up.
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| Figure 1 |
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| Figure 2 |
Video textures can have a special problem that still images and animated
textures do not: interlacing. Even if you are ultimately going to
be distributing using interlaced fields, any source video you use
for textures in your 3D application need to be de-interlaced. When
stretched across the surface of a 3D model, the alternating horizontal
lines can really be distracting (Figure 2). The object on the left
has interlacing problems, which you can see in the staggered horizontal
lines. Interlacing problems are most obvious in clips with fast motion
or camera moves.
DEINTERLACE
In order to make these video textures work well, you need to deinterlace
the fields from the source image prior to using it within your 3D
application. There are a number of ways this can be done and it is
not always explicitly stated how the software will handle the task.
Some apps will throw away one of the fields and duplicate the other,
resulting in a loss of resolution. Some apps will average or blend
the two fields together. Whatever method the software uses, the result
will still look better than using interlaced footage, at least for
our specific example of using video as textures in 3D applications.
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| Figure 3 |
Figure 4
DEINTERLACE
IN 3D
Users of Combustion (and 3ds max) can take advantage of a little known
integration feature to automatically deinterlace the video without
preprocessing. In essence, you use Combustion as your deinterlacing
tool right from within 3ds max. Instead of using the "Bitmap" map
type for the texture, select a "Combustion" map type instead (CWS).
This allows you to either identify an existing project or create a
new one by selecting the Edit button. This launches Combustion and,
in effect, Combustion becomes a built in material editor for 3ds max
(Figure 3). Within Combustion, load the interlaced source clip (in
this case our VideoTraxx clip) and go to the footage node for this
clip. Select lower field dominance (Figure 4). A huge, added benefit
to this integration is the fact that you can decide at any time to
add additional Combustion operations such as color correction, selective
blurs, and so on, again, without rendering it out first.
Gary M. Davis is a production artist and training specialist specializing
in 3D animation and compositing. He is the author of The Focal Easy
Guide to Combustion and can be reached via his website: visualZ.com.
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