Object Space and Parameter Space
Object space is the 3D real number space, which is denoted by the symbol R3. A point in object space is expressed as a coordinate triple (that is, three parameters), denoted by (x,y,z). In ACIS, object space may also be referred to as 3-space or xyz-space. ACIS has been designed around the concept that everything is modeled in a single number space called the model world, which is a subset of object space. The origin, the point (x,y,z) = (0,0,0), is at the center of the model world.
Surface parameter space is the 2D real number space, which is denoted by the symbol R2. A point in surface parameter space is expressed as a coordinate pair (that is, two parameters), denoted by (u,v). In ACIS, surface parameter space may also be referred to as uv-parameter space, uv-space, or simply as parameter space.
Curve parameter space is the 1D real number space, which is denoted by the symbol R1 (or simply R). A point in curve parameter space is expressed as a single coordinate (that is, one parameter), denoted by t. In ACIS, curve parameter space may also be referred to as the real line. The term parameter space alone refers to surface parameter space.
The following figure illustrates the relationship between object space, parameter space, and the real line in ACIS. This figure also lists the ACIS C++ classes that represent entities in each of these number spaces and the ACIS math classes that map from one to the other.
Figure. ACIS Real Number Spaces
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