DG Kernel Documentation

IMetrics can be queried from IModel, ISection and possibly other objects in intermediate updates and releases. Query this interface from an object to check if the object implements the interface.

When queried from IModel this interface returns results related to the whole set of objects. For example GetDimentions() method returns bounding box of the whole model.

Implements also: IMetrics2.

HRESULT Dist( IMetrics * iIMetricObj, MetrDistContext* context, IRelation** nearest, double* dist )

Parameters

iIMetricObj - [in] IMetrics interface implemented by the second object. See remarks.

context - [in] NULL reference or MetrDistContext structure containing additional parameters. When the reference is NULL all defaults are used. See remarks.

nearest - [out] If nearest is not a NULL reference, a IRelation will be retuned in the referred variable. Lists referred to by the relation nearest keep elements of type IVertex. See remarks.

dist - [out] Returned distance between the objects


Remarks:

See also IMetrics2.Dist for a simplified version of this method.

The method calculates the distance between the object implementing the interface and the object where iIMetricObj was queried from. Distance is the shortest distance between any two points belonging to the objects.

The returned nearest interface can be used to investigate set of pairs of mutually nearest points from the two objects.

The size of the set depends on options supplied in the context structure. In the simplest (default) case if context .needAll = false the set consists of a single pair of two nearest points. When there are more than one nearest pair at exactly the same distance, selection of the returned pair is random.

When context.needAll is set to true and d is the minimal distance retuned by the method the set will contain all pairs at distances in range d to d+context.tolerance. Note that when there are infinite numbers of nearest points, like in the case of parallel planes, only a finite number of distinct ones are selected. This selection depends on the geometry of mesh of the surface.

includeChildren member of context is true children of both objects are considered as part of the object.

To obtain information about particular point, call IRelation.GetRelation method of the nearest interface to obtain list of all pairs. Browse the list using its IIterator interface. Retrieve the required pair with a call to IList.GetAt of the list of pairs and cast it to AssociationPair type. Use the obtained posn0 position to obtain IVertex interface from the first list of the nearest relation. The first list is returned from call to IRelation.GetItemList(true) of the nearest IRelation interface. It contains elements of type IVertex. IVertex interface can be used to obtain information about coordinates as well as normal(s) to the surface at the point.

Elements of the pair list are sorted by increasing distance. The nearest two points are listed first. The order is random for pairs at exactly the same distance.

Note 1: that this method is computationally intensive for large models. It is recommended to avoid calling it in a tight loop with context.needAll and/or context.includeChildren set to true. Consider using the IsCloserThan method in this situation instead.

Note 2: The algorithm assumes that the objects do not have internal interentity, i.e. they do not have common points which belong to strictly internal area of both objects. If this happens the algorithm may return incorrectly small positive number.

HRESULT GetDimensions( DIPoint* min, DIPoint* max )

Parameters

min - [out] 3D point in global coordinates (See DIPoint). Coordinates of min a are minimal values of the coordinate for any point in the model.

max - [out] 3D point in global coordinates (See DIPoint). Coordinates of max a are maximal values of the coordinate for any point in the model

Return Values

S_OK in case of success.

Remarks:

This method returns opposite diagonal corners of the minimal box totally containing the model.

HRESULT GetPointLocation( DIPoint* pt, int* location )

Parameters

pt - [in] point location of which is to be found Coordinates must be relative to the local frame of the box if the box is oriented or global is the box does not have a local frame

location - [out, retval] The returned location code. See remarks


Remarks:

Identifies location of the point. The object where this interface was queried from is assumed to be solid (has closed surface). Meaning of the returned location code depends on type of the object, which implements the interface.

In this release this method implemented only by Entities with geometry, which are solids of BRep geometry, Entities with Mesh Geometry and Oriented Boxes.

BRep BSpline Solids

pt must have global coordinates. Values of return codes are enumerated in PointVsSurfaceLocation_DG enumeration:

0 - Unknown location (error code)
2 - Inside internal area of the solid, not on the surface
3 - Outside, not on the surface
4 - On the surface

The default tolerance used in the calculation is 1e-8. It can be modified using PointLocationTolerance parameter of the component context

Mesh Entities

pt must have global coordinates. Return codes:

-1 - Invalid location (error code)
0 - inside internal area of the solid, not on the surface
1 - Outside not on the surface
2 - Coincides with a vertex
3 - Lies on an edge of the mesh
4 - Inside a face of the mesh

Notice that codes greater than 1 indicate that point lies on the surface.

Oriented Boxes

Coordinates of pt must be relative to the local frame of the box if the box is oriented or global is the box does not have a local frame. See Location codes for boxes for the return codes.

HRESULT IsCloserThan( IMetrics * iIMetricObj, double dist, MetrIsCloserThanContext* context, VARIANT_BOOL* closer );

Parameters

iIMetricObj - [in] IMetrics interface implemented by the second object. See remarks.

dist - [in] Value to compare the distance to.

context - [in] NULL reference or MetrIsCloserThanContext structure containing additional parameters. When the reference is NULL all defaults are used. See remarks.

closer - [out] The returned Boolean value. True if the objects have points closer than dist and false otherwise.


Remarks:

The method returns true if the distance between object implementing the interface and the object where iIMetricObj was queried from is less than dist.

If includeChildren member of context is true children of both objects are considered as part of the object. . Default: false

If further member of context is true the method will solve the opposite problem: Return true if there are two points in the objects, which are have distance greater than dist. Default is false

quickCheck member of the context structure allows significant acceleration of the algorithm when two object are either convex or at distance greater than maximal distance between any two adjacent vertexes of the mesh. Set it to false is not sure. It should be true if it is expected that some straight line between any two points of one object can intersect with another object.

This method is supplied as alternative to Dist method for applications like collision detection. In most cases it offers better performance. For collision detection it is recommended to use calls to this method between changes in the object(s) position or orientation. If needed, once the method returns false (collision) the Dist method can be called to retrieve information about the nearest points.

Note: The algorithm assumes that the objects do not have internal interentity, i.e. they do not have common points which belong to strictly internal area of both objects.