Objects in <#348#><#1843#>rayshade<#1843#><#348#> are composed of relatively simple <#349#>primitive<#349#> objects. These primitives may be used by themselves, or they may be combined to form more complex objects known as <#350#>aggregates<#350#>. A special family of aggregate objects, <#351#>Constructive Solid Geometry<#351#> or CSG objects, are the result of a boolean operations applied to primitive, aggregate, or CSG objects.
This chapter describes objects from a strictly geometric point of view. Later chapters on surfaces, textures, and shading describe how object appearances are defined.
An <#352#>instance<#352#> is an object that has optionally been transformed and textured. They are the entities that are actually rendered by <#353#><#1845#>rayshade<#1845#><#353#>; when you specify that, for example, a textured sphere is to be rendered, you are said to be instantiating the textured sphere. An instance is specified as a primitive, aggregate, or CSG object that is followed by optional transformation and texturing information. Transformations and textures are described in Chapters 7 and 8 respectively.