Length of contact 2dSee full documentation

measure allowing to compute length of contact between shapes

This measure allows to compute the portion of contour of a shape which is in contact with its neighbors.

Length of contact for a shape composed of a collection of segments is computed as followed :

We parse all segments from shape and for each we check whether segment fulfil contact policy requirement with another shape. If this is the case we considers that whole segment length is in contact with other shapes.

Measure parameters

Distance of contact

Given the fact that input data are discreet, notion of contact is defined with respect to a distance threshold ContactDist parameter. Length of contact will be accounted for distances lower or equal to this user parameter.

Contact policy

On following figures, we represents :

• portion of segments of interest in green if segments are considered to be in contact area, in red otherwise.
• polygonal approximation associated to other shapes in grey.
• shortest distance to nearest shape in dotted green if segment is in contact, in dotted red otherwise.
• distance which are not minimal in dotted orange
• point(s) from which computation has been done in blue

Contact policy parameter ContactPolicy takes the following values :

• ipsdk::geom::eSegmentContactPolicy::eSCP_SegCenter : in this case we compute distance from center of current segment to other shapes.
  
• ipsdk::geom::eSegmentContactPolicy::eSCP_SegEnds : in this case we compute maximum distance from current segment ends to other shapes
  
• ipsdk::geom::eSegmentContactPolicy::eSCP_SegClosestPoint : in this case we compute distance from current segment to other shapes (closest point on segment to other shape)
  

Segments sub sampling

At last, measure parameter SegmentSubSamplingStep allows if set to requiere sub sampling of shape segments.

This parameter allows to make computation much more precise with the drawback of greater computation cost.

Process holes

An additional parameter flag ProcessHoles allows to specify whether shape holes should be taken into account during computation. Please see Distance to nearest neighbor 2d for an explanation of effects of this flag.

Asymmetry of measure

Note that this measure is not symmetric since length of contact of a first particle to a second one may not be the same as the length of contact of second particle to the first one. This fact is illustrated by following figure where length of contact of left shape is paint in green while length of contact of right shape is paint in orange :

Examples

In next figures, shapes (ie. the polygonal approximation of their boundary), are colored with respect to the length of associated contact.

Here is an example of the effect of contact distance threshold parameter ContactDist on computation results (please take care of scale bar values), in this case :

• we do not require data sub sampling
• contact policy is set to segments center
  

Here is an example of the effect of contact policy parameter ContactPolicy on computation results (please take care of scale bar values), in this case :

• we do not require data sub sampling
• contact distance is set to 5
  
  User can note that in this case, results are very sensitive to used contact policy.

Here is an example of the effect of contact policy parameter ContactPolicy on computation results (please take care of scale bar values), in this case :

• we do require data sub sampling with a step of 1 pixel
• contact distance is set to 5
  

measure allowing to compute length of contact between shapes

Measure synthesis :

Measure Type	Measure Unit Type	Parameter Type	Result Type	Shape Requirements
Geometry 2d	Length	LengthOfContact2dMsrParams	Value (ipsdk::ipReal64)	Boundary Approximation

See Shape measurement for additional information on these pictograms