Model space is the conceptual area where the separate components of a picture, defined in world space, are brought together. To assemble one or more primitives from world spaces to model space, the application specifies the transformations to occur. Then the PM applies them to each of the components. Model transformations convert world coordinates to model-space coordinates. For example, an octagon and the word STOP, defined individually in separate world-coordinate spaces, can be assembled into a stop sign in model space.
Graphics applications can have more than one model space. If there is more than one model space, the picture components are assembled in page space. If an application has each model space in a different segment, the model transforms are reset for each segment.
An application can use a viewing limit clipping area to define the part of a model space to place in the next coordinate space (the page space). A viewing limit is always rectangular, and the coordinates that define its location and dimensions are always model coordinates.