GeometryHelper.CommonGeometry 4.0.0

GeometryHelper.CommonGeometry

The types that GeometryHelper.PlaneGeometry and GeometryHelper.SolidGeometry both need. It exists so that a program using the two libraries together sees one Tolerance and one Angle rather than two of each, which is what happens when a shared type is copied into both.

It depends on nothing and knows nothing about either library.

Installation

dotnet add package GeometryHelper.CommonGeometry

Both geometry libraries pull it in on their own, so install it directly only when you want Tolerance or Angle without either of them.

Tolerance

Every comparison in either library that can be affected by floating point error takes a Tolerance, and every such method has an overload without one that reads Tolerance.Global. Neither library compares coordinates with ==.

EqualPlanar is separate from EqualPoint because coplanarity is measured far from the reference point. A face twelve metres long that is tilted by a hundredth of a degree deviates by about two millimetres at its far end — far more than EqualPoint allows, yet still flat enough to work with. Only GeometryHelper.SolidGeometry uses it.

// One setting for both libraries.
Tolerance.Global = new Tolerance(equalPoint: 1E-3, equalVector: 1E-3);

// Or pass one explicitly, which is what to do when a single operation needs to be looser or
// tighter than the rest of the program.
bool same = first.IsEqualTo(second, new Tolerance(1E-6, 1E-6));

Tolerance.Global is a single shared setting. Changing it for a drawing in the plane changes it for a model in space as well.

Angle

An angle stored in radians and readable as either unit. There is deliberately no public constructor taking a bare double: a number on its own does not say which unit it is in, so the unit is named at the point of creation.

Angle right = Angle.FromDegrees(90.0);
double radians = right.Radians;          // 1.5707963...

Angle turned = right + Angle.FromDegrees(300.0);
Angle wrapped = turned.Normalize();       // into [0, 2π)
Angle signed  = turned.NormalizeSigned(); // into (-π, π]

Normalize and NormalizeSigned differ in where they put the cut: the first is what to use for a bearing, the second for a difference between two directions, where -170° is a nearer answer than 190°.

PointLocation

Where a point sits relative to a shape: Inside, OutSide, or OnSide.

What counts as Inside depends on the family the shape belongs to. A volume encloses a region of space. A region encloses an area — in space that means a point counts as inside only when it lies on the carrier plane as well as within the boundary. A curve encloses nothing and never reports Inside.

PlaneSide

Which side of an oriented plane a point lies on: Above, Below, or On. The sides are named after the plane normal rather than after world up, because a plane carries its own orientation and may point anywhere.

Licence

MIT.