In general, with the following program :
Plimit domain;
tdomain (&domain);
tscene (scene_id, &struct_id_list, view_ind);
the pset_local_tran and pset_model_clip_vol elements are inserted in the structure scene_id and the matrix (parameter of pset_local_tran function) transforms all points (X,Y) into a point (X',Y') with :
X' = (X-domain.x_min)/(domain.x_max - domain.x_min)
Y' = (Y-domain.y_min)/(domain.y_max - domain.y_min)
and with the following program :
Plimit3 domain;
tdomain3 (&domain);
tscene (scene_id, &struct_id_list, view_ind);
the pset_local_tran3 and pset_model_clip_vol3 elements are inserted in the structure scene_id and the matrix (parameter of pset_local_tran3 function) transforms all points (X,Y,Z) into a point (X',Y',Z') with :
X' = (X-domain.x_min)/(domain.x_max - domain.x_min)
Y' = (Y-domain.y_min)/(domain.y_max - domain.y_min)
Z' = (Z-domain.z_min)/(domain.z_max - domain.z_min)
In conclusion, if the structure scene_id is posted on a workstation with the identifier ws_id, a traversal set off on ws_id transforms all points of the structures in the scene with coordinates inside the domain, into a point inside the space [0-1, 0-1, (0-1)] in WC (World Coordinate)
This is called a scene transformation
N.B. : If the domain to be transformed is not square (in 2D) or cubic (in 3D), the data is distorted during traversal by the scene transformation (the height/width ratio data is not maintained in WC). To avoid this problem, always work with a square or cubic domain which fits the given data as closely as possible.
In 2D the most practical method consists of choosing the smallest square capable of containing the data limit rectangle and with the same center :
Similarly, in 3D, the most practical method consists of choosing the smallest cube capable of containing the data limit parallelepiped, and with the same center :
Note that the view index attribute is positioned at the start of the scene_id structure : the view index view_ind is therefore used by all the primitives in all the structures called by the scene.