A QuadMershGO.T is a geometric object that describes a quadrilateral mesh. A quadrilateral mesh is defined by a 2-dimensional array of points. Neighboring points are connected by quadrangles.

INTERFACE QuadMeshGO;

IMPORT Color, GO, Point3, SurfaceGO;

EXCEPTION BadSize;
EXCEPTION ColorsUndefined;

TYPE
  T <: Public;
  Public = SurfaceGO.T OBJECT
  METHODS
    init (READONLY pts : ARRAY OF ARRAY OF Point3.T;
          s := GO.Shape.Unknown) : T;
    addFacetColors (READONLY cols : ARRAY OF ARRAY OF Color.T)
        RAISES {BadSize};
    setColorOfFacet (i, j : INTEGER; c : Color.T) RAISES {ColorsUndefined};
  END;

qm.init(pts,s) initializes the quad-mesh qm and returns it. pts is the matrix of points defining the quad-mesh; s is a `shape hint'', i.e.\ a hint whether each polygon of the quad-mesh is convex, non-convex, or complex. Refer to the \interface{GO} interface for details on shape hints. By default, the quad-mesh is drawn in the color specified by the \type{SurfaceGO}{Colour} property.

qm.addFacetColors(cols) overrides the surface color specified by the \type{SurfaceGO}{Colour} property, and instead attaches an individual color to each quadrangle. The quadrangle (i,j) (i.e. the quadrangle specified by the points pts[i][j], pts[i][j+1], pts[i+1][j+1], pts[i+1][j]) is drawn in col[i][j]. If pts was an $m+1 \times n+1$ array, cols must be an $m \times n$ array; otherwise, the exception BadSize is raised.

qm.setColorOfFacet(i,j,c) changes the color of quadrangle (i,j) to be c. The exception ColorsUndefined is raised if no facet colors have yet been attached to qm. It is a fatal error if i or j specify an invalid quadrangle. {\em I should instead raise an exception!}

{\em NOTES: (a) Points and colors should be exposed as properties. Refer to the \interface{PolygonGO} interface for an idea about how to do that. (b) It should be possible to attach single color values; in this case, all cells with a missing color value are drawn in the color specified by SurfaceGO.Colour.}

END QuadMeshGO.