A model is a collection of geometric pieces known as meshes that
together represent the complete object. A mesh is a single object
such as a head, the torso, the legs, a sword, and so forth.
XNA makes loading models easy for developers, whereas in
OpenGL and Direct3D (excluding X models in Direct3D 9 and
before) the loading and rendering of geometry falls solely on the
programmer. The ease at which geometry can be loaded was first
discussed in Chapter 7 where it was mentioned that the content
pipeline function Load() can be used to load an X or FBX model file.
In Chapter 10 we’ll see how we can create our own content import
-
ers and processors, effectively giving us the ability to create code to
load any type of file that we would want to use. This includes load
-
ers for other model formats besides the standard X and FBX
importers and processors that ship with XNA.
XSI and XNA
Softimage provides one of the leading 3D modeling and animation
packages for creating assets for video games, known as XSI. The
XSI package comes with a very powerful 3D rendering and anima-
tion engine and is used by many different professional video game
developers such as Valve, CAPCOM, Lionhead Studios, Pandemic,
and many more to create 3D resources for their games.
Softimage, Microsoft, and Valve Software together bring us the
XSI Mod Tool, which is a version of the XSI package that allows
anyone to practice and create content for video games for free. The
retail XSI packages each offer features that are not found in the XSI
Mod Tool. The limitations of the XSI Mod Tool include the follow
-
ing, most of which would have a large impact on non-game
developers, such as those working in movies and TV:
n
Does not support mental ray materials
n
Maximum polygon count for exported geometry is 64,000
n
Rendered images created with the Mod Tool have a maximum
resolution of 512 × 512
n
Normal maps generated with the Mod Tool have a maximum
resolution of 512 × 512
n
Only supports polygonal meshes
n
Majority of mental ray rendering features disabled
300 Chapter 9
Although the XSI Mod Tool does have its limitations, luckily very
few of them affect video games or are otherwise acceptable from a
powerful and free tool. Some of the limitations, such as normal
maps having a max resolution of 512 × 512, can be avoided by using
other tools to create normal maps such as NVIDIA’s Melody, which
is also free to download and use. The biggest limitation is the
64,000-polygon count, but most single objects will not be made up of
that many polygons in most cases, especially in non-AAA game
titles. Whether any of these limitations are actual limitations
depends on what is being created for your projects. Since XSI can
be used to create content for movies and television (such as the
movie Shrek), many of these limitations are huge. Once you are
familiar with XSI and have become skilled at using it, you can
always look into purchasing one of the retail versions for more
power.
The XSI Mod Tool supports creating Half-Life 2 mods and offers
XNA integration. When you create an XNA project, you can also
create an XSI project and link the two together. This is done by
clicking on XNA Game Studio in the menu bar and selecting Con-
nect to XNA Project as seen in Figure 9-5.
When the dialog box appears, choose the path of the XNA project
you wish to connect to (see Figure 9-6); when you export geometry
it will save it in the location of your XNA project. Any shaders and
textures or other resources that are used by the exported geometry
are also saved. Connecting to an XNA project essentially means that
the XNA project location is the location that XSI will give you the
option of saving various files (such as scenes, models, etc.) and
3D Graphics 301
Figure 9-5: Connecting to an XNA
project with XSI.

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