Programming the DG Kernel Control
Manipulation of a model and its rendering properties is performed
via interfaces implemented by DG Kernel control. Interface is a simple notion,
which does not require any special knowledge. Interface is a small group of
methods (functions) related to a certain functionality.
Programming Samples provide ample examples of their
usage.
DG Kernel interfaces are organized
in a hierarchical fashion. This means that one have to traverse the interface hierarchy tree using
casts and other methods to obtain needed interface of a particular object.
IModel_DG is the root interface for geometry-related interfaces, from which all
its dependent interfaces can be obtained.
IModel_DG interface can be obtained by calling GetModel() method
of the control and query/cast IModel_DG from it.
The interface hierarchy can be traversed using casts (or QueryInterface() calls in C++) and other
interface methods like IModel_DG::GetEntity() to obtain
the interface needed and call its methods.
IView_DG interface is the root for functionality related to 3D rendering and user interaction. IView_DG reference is
returned by query GetView() > IView_DG.
In unmanaged environments like native C++, every interface reference, obtained with the QueryInterface() or
a call to an interface method, should be released with a call to Release()
method, like pIModel->Release(), when
it is no longer needed. This can be made seamless by using smart pointers. See C++ samples for an example.
C++ interface declarations are available in DgInterface.h located in
Samples\VC\Include directory of the installation folder. The same folder contains DIError.h with declarations
of error codes specific to DInsight software. All other return
codes for interface methods are contained in Winerror.h - the standard header file
of your development environment. If you cannot find one on your
machine use copy from Samples\Vc\Include directory of this product installation
folder.
Microsoft Visual Basic and Microsoft Visual Studio .NET detect control's interfaces and types automatically after the
control has been added to the project. To access this information open Object
Browser and activate KernelCADTypeLib set.
Advanced: DG Kernel software slightly deviates from
the COM standard. In some (rare) situations, traversing
the Interface Hierarchy can obtain interface implemented by an object different
from the original one. This means that result of a query depends on the query
path. For example for an entity with 3DS geometry, path IEntity_DG > IArray
returns IArray of its child entities, but path IEntity_DG > IAxiBase > IArray
returns IArray of its base knots.
See also Interface queries
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