Using Airbrush requires
that you have some working knowledge of how 3d shapes in general work.
If you do not understand terms such as LOD nodes or point normals, you
may want to read this section
How
a 3d shape is put together:
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A single shape in FA (a .sh file) is actually a collection of several individual shapes. These "sub shapes" are referred to as meshes. Airbrush does not allow you to work with a shape as a whole -- you can only edit individual meshes. This does not mean that you can't edit all aspects of a shape -- only that you must edit them one at a time.
There are generally two kinds of meshes in an FA shape: Level of detail nodes, and animation nodes.
Level-of-detail nodes (LOD nodes), which are used to speed up the game. By having several representations of an object, each with less detail, it is possible to avoid rendering detail with would be invisible because the shape is too far away from the camera. Look at the LOD nodes of SACRAM.SH:
As you can see, lower levels have fewer polygons, and are thus "cheaper" to draw. By drawing only what will be seen, the game can run a lot faster.
The second type of
mesh is an animation node. These are landing gear, flaps, rudders etc.
which move independently relative to the shape -- for instance, if you
have a plane flying at heading 250, with the rudder deflected 10 degress,
the rudder is actually heading 240. In FA, it is usual for LOD 1 (the highest
detail LOD) to have several anim nodes, LOD 2 to have only one (the undercarriage),
and LOD 3 usually has none (because they would be too small to see at the
distances at which LOD 3 is selected).
The
structure of a mesh:
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A shape file is simply a serial sequence of mesh definitions, all tacked on end-to-end. Understanding a single mesh means understanding the lot.
A mesh has two main parts: vector definitions, and polygon definitions. These two together provide the information necessary for the FA and Airbrush rasterizing routines to draw the polygons which come together to make a shape. Although polygons give the shape the physical properties you see (such as colour, shading, texture, etc.), it is in fact the vector definitions which give a polygon its particular shape - the positions in space of the corners of the polygon. Have a look at the following pictures of vectors only, and polygons with vectors overlayed:
Vertices only -
they give the mesh its shape
With the edges of
the polygons shown, the shape becomes more evident
With polygon material
properties on, you have the actual mesh.
Gear,
rudder, flaps and other animated things:
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Part of the complication of an SH file comes into the fact that the rudders, etc. are in fact represented as separate meshes. So, a shape will have three representations of the rudder - one deflected to port, one amidships and another to starboard. When modifying a shape, you need to edit all of these subshapes, or suddenly your flaps might change colour when they are lowered!
Exceptions to this
rule are the sort of animated parts that move smoothly, such as swinging
wings, AWACs radomes, and the engines on the Osprey. For these shapes,
only one mesh is given.
Polygon
shading styles:
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Not all polygons
are rendered using the same techniques. Fighters Anthology uses three techniques
of polygon rendering:
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The tail art, nose art and nationality roundels are not textured onto a plane itself. In fact, small, transparent polygons are laid just on top of the body, and these are textured with the roundel or whatever.
Any polygon which is camouflaged (ie. has the bitmap part of th camo on it) is in effect texture mapped. If you want texture rich models, look at these planes first (eg. don't edit the MiG-29 shape, but rather go for the camouflaged (but otherwise identical) MiG-29M shape).