A level object corresponds to 'directories' or 'folders' in Disk Operating systems.
Level objects allow all geometric objects in Realsoft 3D to be grouped into a hierarchical tree structure. For example, a table consists of two sub objects: a base and a cover. The base consists of any number of sub objects, such as legs and so on.
All geometric objects, including levels, have a 4x4 matrix associated with them. This matrix defines so called local object space for the object. All geometric attributes for the object are defined in this local space.
Linear transformations are applied to an object by combining a 4x4 transformation matrix to the object space matrix of the object. This transforms the geometry of the object, as well as the geometry of the sub objects. The 4x4 matrix is usually represented to the user as four vector fields: Translate, Scale, Rotate and Skew, but it can also be manipulated directly through scripts or the SDK.
The level object also plugs in a feature called 'Boolean Operations'. If the type of the level is 'Union' (OR) , then all the matter defined by the sub objects of the level is added into the universe. In other words, the logical operation between the sub object is OR.
Levels also allow geometric objects and material description objects to be grouped into a single entity. For example, one can create a wooden sphere by creating a level consisting of two sub objects: a sphere and a 'wood' mapping object. The level object property gadget includes the following controls:
Boolean union (OR) - The sub objects add matter to the scene i.e. the volume of the level is the sum of the sub volumes.
Boolean Intersection (AND) - The volume of the level is the intersection of the sub volumes.
Boundary surface solid - The surfaces of the sub objects are combined to define a volume in space. With this option, you can build a solid object from surfaces that do not define a natural volume themselves (a set of NURBS patches, SDS objects etc.). The surfaces should form a closed system without holes, otherwise rendering errors may appear.
Material mapping average - This option is useful for combining several materials into a weighted average. Most materials replace the result of the previous material: adding marble over a wooden sphere makes it look marble. With the mapping average level, you can make a weighted mixture of the materials, say 70 % marble, 30 % wood. The weight of each material can be defined using the 'Scope' value of the corresponding mapping object, or by assigning a scope value in each material.