Game Development Reference
In-Depth Information
Cameras
Cameras come in two basic forms, the camera that moves with the action
and the camera that is fixed. One simple way to use the camera is to
attach it to the user's character. Using this technique, the user always
gets the same view of the character. Another method is to let the camera
swing around as the player moves about the environment. While
considerably more complex to implement, this has a much more filmic
feel. If the game environment lends itself to a grid structure then the
camera direction can be stored in a three-dimensional array. As the player
moves from one block to the next, the transformation engine will probably
use quaternion interpolation to swing the camera orientation around. The
details of this are best stored in a scene level camera structure.
Scripts, user control and behaviours
Unless the scene is strictly linear, with no interaction, then a scene must
store the details about how the interaction occurs. This may include
scripts, how the user interacts with the scene resources. Often, a user will
control a central character and the scene must know how this control is
handled. Each character in an interactive scene will have a set of
behaviours. A character may have an animation loop for walking, running,
falling, jumping, etc. The behaviour policy will link the condition of the
game and the user control to an appropriate behaviour for the
character.
Texture objects
Real-time 3D character animation makes extensive use of textures to add
detail to a scene that cannot be achieved via more complex geometrical
models. Textures can be stored at the object level, the scene level or the
global level. Characters that appear infrequently and use unique textures
should use textures that are assigned at the object level, while the central
character if she appears in several scenes would be a good candidate for
a texture that is stored at the global level. Scene level texture storage
applies to characters that appear only in a specific scene and make use
of textures that appear only in that scene. Texture objects are stored in an
array and are accessed when rendering via the OpenGL texture ID. Each
polygon in a scene has a surface index into the surface list. The surface
list contains a pointer to a texture. The texture contains the OpenGL
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