MC (Modelling Coordinate) space contains the coordinates of the structures' graphics primitives, prior to their transformation by transformation sets (see element PSLMT, PSGMT, PSLMT3, and PSGMT3)
WC (World Coordinate) space contains the coordinates after transformation. If the CSS contains no PSLMT, PSGMT, PSLMT3, or PSGMT3 elements, MC space is considered to be identical to WC space.
E.G. : The table below consists of a top and 4 legs,
and is modelled by a program building 3 structures with the following hierarchy
If no transformation sets are inserted in the root structure S0, the 4 legs are all in the same position above the origin (0,0,0) of the table top. They are in the wrong place and also too big, in relation to the size of the top.
The easiest solution is to insert a transformation set for each of the 4 legs. These sets reduce the size of the legs (scaling) and move each leg to one of the 4 corners of the table top. As it is unnecessary to insert a transformation set for the table top, the coordinates of the table in WC space are between 0 and 2 (the MC space of the table top may be said to be identical to WC space).
The parent structure S0 is made up of the following elements :
C table top
CALLPEXST (S2)
C 1st leg set M1 is built using the PTR3 and PSC3 utilities CALLPSLMT3 (M1,PCREPL) CALLPEXST (S1) C 2nd leg set M2 is built using the PTR3 and PSC3 utilities CALLPSLMT3 (M2,PCREPL) CALLPEXST (S1) C 3rd leg set M3 is built using the PTR3 and PSC3 utilities CALLPSLMT3 (M3,PCREPL) CALLPEXST (S1) C 4th leg set M4 is built using the PTR3 and PSC3 utilities CALLPSLMT3 (M4,PCREPL) CALLPEXST (S1)