Base class of topological shapes. More...

#include <cadex/ModelData/Shape.hxx>

Inheritance diagram for cadex::ModelData::Shape:

Public Member Functions
ShapeType	Type () const
	Returns a shape type. For a null object returns Undefined.

ShapeOrientation	Orientation () const
	Returns orientation flag.

Shape	Reversed () const
	Returns a shape that shares the same geometry and subshape graph but has opposite orientation.

Shape	Oriented (ShapeOrientation theOrientation) const
	Returns a shape that shares the same geometry and subshape graph and has specified orientation.

bool	IsEqual (const Shape &theOther) const
	Returns true if the shape shares the same geometry and subshape graph, and has equal orientation.

bool	IsSame (const Shape &theOther) const
	Returns true if the shape shares the same geometry and subshape graph.

void	SetName (const UTF16String &theName)

UTF16String	Name () const

Public Member Functions inherited from cadex::BaseObject
size_t	Id () const
	Return unique identifier of public object.

internal::BaseObjectImpl *	Impl () const

bool	IsNull () const

	operator bool () const

template<typename T >
bool	IsOfType () const

template<typename T >
T *	Impl () const
	Reserved for internal use.

Static Public Member Functions
static bool	CompareType (const BaseObject &theObject)
	Check the type of object. Returns true if the specified object is this class type.

Protected Member Functions
	Shape (const ImplType &theImpl)

Protected Member Functions inherited from cadex::BaseObject
	BaseObject (const ImplType &theImpl)

Additional Inherited Members
Public Types inherited from cadex::BaseObject
typedef std::shared_ptr< internal::BaseObjectImpl >	ImplType

Detailed Description

Base class of topological shapes.

Topological shapes define boundaries of the geometrical entities (curves and surfaces) in B-Rep.

Some topological entities refer to geometrical entities (e.g. edge refers to curve and face refers to surface), whereas some only refer to child topological entities (e.g. wire refers to edges it consists of or shell refers to faces it consists of).

Types

Refer to Shape Types for the list of supported shape types. Type() returns a type as enumeration value which can be used to downcast to a respective subclass type, for instance:

ModelData::Shape aShape = ...;
if (aShape.Type() == ModelData::ShapeType::Face) {
    const ModelData::Face& aFace = static_cast<const ModelData::Face&> (aShape);
    ModelData::Surface aSurface = aFace.Surface();
    ...
}

Orientation

Each shape can have either forward or reversed orientation as returned by the Orientation() method. Meaning of orientation depends on the shape type:

For vertex, orientation has a meaning only in context of a parent edge where forward vertex corresponds to smaller parameter on the edge curve and reversed vertex to greater parameter.
For edge, orientation specifies whether edge direction is aligned or is opposite to underlying curve orientation.
For face, orientation specifies whether face normal is aligned or is opposite to underlying surface normal.
For wire, shell, solid, or body, orientation simply specifies whether subshapes should be considered with their own or opposite orientations. For instance, a reversed wire would be similar to a forward wire consisting of original edges taken with opposite orientations.

A shape with the opposite orientation can be returned with the Reversed() method. A shape with a specified orientation can be returned with the Oriented() method. Both methods create a shallow copy of the original shape, which shares a subshape graph but has a distinct orientation flag.

Equality and similarity relationships

Two shapes are considered equal if they share the same definition (i.e. geometry and subshape graph) and have equal orientations. The method IsEqual() and operator==() can be used to check equality.

Two shapes are considered same if they share the same definition (i.e. geometry and subshape graph). Orientations are not required to be same. The method IsSame() can be used to check this relationship. Obviously, the 'IsSame' relationship is less strict than 'IsEqual'.

The following code snippet demonstrates both relationships:

ModelData::Shape aShape1 = ...;
 
//shapes with equal orientations are IsSame() and are equal
ModelData::Shape aShape2 = aShape1;
assert (aShape2 == aShape1);
assert (aShape2.IsSame (aShape1));
 
//shapes with opposite orientations are IsSame() but are not equal
ModelData::Shape aShape3 = aShape1.Reversed();
assert (aShape3.IsSame (aShape1));
assert (aShape3 != aShape1);

For example, a closed shell contains pairs of IsSame() edges but with opposite orientations.

Exploration of Subshapes

Children subshapes can be retrieved using ModelData::ShapeIterator. Iterator supports two usage scenarios:

iteration over direct children (e.g. faces of a shell);
iteration over subshapes of a specified type (e.g. all edges inside a shell).

Refer to ModelData::ShapeIterator for detailed explanations of both scenarios.

Resulting orientation

Orientation of a returned subshape is product of own subshape orientation (stored inside a subshape) and of its parent. Thus, if the subshape and its parent both have the same orientation then the returned subshape will have forward orientation, if they have opposite orientations then the returned subshape will have reversed orientation.

When exploring nested subshapes the same rule applies at each level of the hierarchy:

Resulting_orientation = parent_orientation * subshape_orientation * subsubshape_orientation * ...

For instance, when exploring a forward face, which has a wire with reversed orientation, with an edge having forward orientation, exploring that edge will return an edge with reversed orientation.

Storing Shapes in Containers

ModelData::Shape has a single data member, a shared pointer pointing to internal implementation (i.e. follows a 'pimpl' design pattern). ModelData::Shape subclasses do not add any own data fields. Therefore it is safe to store objects (even of different subtypes) in containers by value:

std::list<ModelData::Shape> aShapeList;
ModelData::Shape::Iterator anIt (aShape);
while (anIt.HasNext()) {
    aShapeList.push_back (anIt.Next());
}

Storing Shapes in Associative Containers

Shapes can be stored in associative containers (such as std::unordered_map or std::unordered_set) as keys. Hash and equality functors required for such containers can be selected depending on desired behavior, whether the container must ensure uniquness defined in terms of equality or similarity relationships (see above):

ModelData::OrientedShapeHash and ModelData::OrientedShapeEqual – for uniqueness in terms of 'IsEqual' relationship;
ModelData::UnorientedShapeHash and ModelData::UnorientedShapeEqual – for uniqueness in terms of 'IsSame' relationship;

Refer to Equality and similarity relationships for relationship definitions.

The following code snippet demonstrates usage of both approaches:

typedef std::unordered_map<ModelData::Shape,
    int,
    ModelData::OrientedShapeHash,
    ModelData::OrientedShapeEqual>           OrientedShapeMap;
 
typedef std::unordered_set<ModelData::Shape,
    ModelData::UnorientedShapeHash,
    ModelData::UnorientedShapeEqual>         UnorientedShapeSet;
 
// Returns true if the shell is open, i.e. has edges belonging to single face only.
static bool HasFreeBoundaries (const ModelData::Shell& theShell)
{
    UnorientedShapeSet aSet;
    ModelData::ShapeIterator i (theShell, ModelData::SapeType::Edge);
    while (i.HasNext()) {
        const auto& aShape = i.Next();
        auto r = aSet.insert (aShape);
        if (!r.second) { //if the same edge was already encountered then remove it
            aSet.erase (r.first);
        }
    }
    return !aSet.empty();
}

Examples: MTKConverter/Program.cs, and MTKConverter/main.cxx.

Member Function Documentation

◆ IsEqual()

bool cadex::ModelData::Shape::IsEqual ( const Shape & theOther ) const

Returns true if the shape shares the same geometry and subshape graph, and has equal orientation.

See also: Equality and similarity relationships, IsSame().

◆ IsSame()

bool cadex::ModelData::Shape::IsSame ( const Shape & theOther ) const

Returns true if the shape shares the same geometry and subshape graph.

See also: Equality and similarity relationships, IsEqual().

◆ Orientation()

ShapeOrientation cadex::ModelData::Shape::Orientation ( ) const

Returns orientation flag.

See also: Reversed(), Oriented().

◆ Oriented()

Shape cadex::ModelData::Shape::Oriented ( ShapeOrientation theOrientation ) const

Returns a shape that shares the same geometry and subshape graph and has specified orientation.

See also: IsSame(), Reversed().

◆ Reversed()

Shape cadex::ModelData::Shape::Reversed ( ) const

Returns a shape that shares the same geometry and subshape graph but has opposite orientation.

See also: IsSame(), Oriented().

Public Member Functions

Static Public Member Functions

Protected Member Functions

Additional Inherited Members