MC (Modelling Coordinate) space contains the coordinates of the structures' graphics primitives, prior to their transformation by transformation matrix (see element pset_local_tran, pset_global_tran, pset_local_tran3, and pset_global_tran3)
WC (World Coordinate) space contains the coordinates after transformation. If the CSS contains no pset_local_tran, pset_global_tran, pset_local_tran3, or pset_global_tran3 elements, MC space is considered to be identical to WC space.
E.G. : The table below consists of a top and 4 legs,
If no transformation matrices 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 matrix for each of the 4 legs. These matrices 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 :
/* table top */
pexec_struct (S2)
/* 1st leg */
matrix M1 is built using the ptranslate3 and pscale3 utilities
pset_local_tran3 (M1,PTYPE_REPLACE)
pexec_struct (S1)
/* 2nd leg */
matrix M2is built using the ptranslate3 and pscale3 utilities
pset_local_tran3 (M2,PTYPE_REPLACE)
pexec_struct (S1)
/* 3rd leg */
matrix M3is built using the ptranslate3 and pscale3 utilities
pset_local_tran3 (M3,PTYPE_REPLACE)
pexec_struct (S1)
/* 4th leg */
matrix M4 is built using the ptranslate3 and pscale3 utilities
pset_local_tran3 (M4,PTYPE_REPLACE)
pexec_struct (S1)