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Working with Models

Any 3D engine needs to be prepared to render 3D models. DirectX offers some default file formats and some functions that will load them in for you, but this page will talk about the basics of what you need, instead of focussing on how a particular API can handle them for you.

This discussion will focus on rigid models. That is, models that don't change their shape.

All models are made up of the following components:

Vertices - These are the points that make up the model. There may be more points that are not actually part of the rendered surfaces, as you will see later.
Surfaces - these are lists of vertices. you have to decide if the vertices will maek up the surface in a clockwise or counterclockwise direction. Each reference to a vertex should also contain coordinates within the texture, if a texture is used. The surface itself should refer to a texture. For more advanced study, surfaces can use multitexturing as well.
Normals - these can eist at the surface or the vertex level. Surface level normals will make the surface appear flat when lighting is enabled. Vertex level normals will make the model appear rounded. The 3D engine should be able to handle both possibilities.
Textures - Each surface should reference a texture if one is used

Other attributes that can complicate the design of the model are as follows:

Some surface may not be affected by lighting
Surfaces may or may not use a texture
Surfaces may or may not use alpha blending (at the surface vertex level or the texture level)

As much as possible, code to handle batch states. If the entire model does not use alpha blending, then the model rendering routine should not bother checking for it. You may code a separate routine that checks for alpha blending. Same goes for lighting.

Vertices could optionally have names attached to them. This allwos other kinds of implementations to refer to vertices by name instead of using a direct reference. Such circumstances might include the necessaity of handling glare points, such as those found on lamp posts at night. Or they could represent weapon hardpoints. Such vertices will likely have orientations attached to them as well.

Other more advanced problems are the implementation of hardpoint and galre point structures. The hardpoint system could be an entire class in itself, also requiring game obejct specific context data to handle the current state. Glare points could also have varying intensity and angle viewing aspects.

Another possibility is the implementation of thrust fire. A group of poitns and one central point (or possibly two points to represent the extremes) make up the flame and are referred to for purposes of special rendering. the flame would be animated, and the flame would certianly give off a flare point, if desired.