Struct TriEdgeCoord

Immutable canonical representation of a shared edge between two adjacent triangles in a triangular grid.

Implements

IEquatable<TriEdgeCoord>

Inherited Members

object.Equals(object, object)

object.GetType()

object.ReferenceEquals(object, object)

Namespace: Scylla.Core.Structures

Assembly: ScyllaCore.dll

Syntax

public readonly struct TriEdgeCoord : IEquatable<TriEdgeCoord>

Remarks

Every internal edge is shared by exactly one downward triangle and one upward triangle. The TriEdgeCoord uses a canonical form: the anchor is always the downward triangle (A + B + C = 1), identified by its (A, B, C) lane coordinate, and the Direction specifies which of its three sides this edge belongs to.

The three edge directions map to upward neighbors as follows:

• A: edge between downward (a,b,c) and upward (a+1,b,c).
• B: edge between downward (a,b,c) and upward (a,b+1,c).
• C: edge between downward (a,b,c) and upward (a,b,c+1).

Use GetCellsNonAlloc(TriEdgeCoord, Span<TriCoord>) to retrieve the two triangles sharing this edge, GetCornersNonAlloc(TriEdgeCoord, Span<TriCornerCoord>) for the two corner vertices, and GetEdgesOfCellNonAlloc(TriCoord, Span<TriEdgeCoord>) to enumerate all edges of a given triangle. Per-edge data can be stored in a TriEdgeMap<TData>.

Constructors

TriEdgeCoord(int, int, int, TriEdgeDirection)

Creates a new triangle edge coordinate from the downward anchor triangle's lane values and the edge direction.

Declaration

public TriEdgeCoord(int a, int b, int c, TriEdgeDirection direction)

Parameters

Type	Name	Description
int	a	The A lane value of the downward anchor triangle.
int	b	The B lane value of the downward anchor triangle.
int	c	The C lane value of the downward anchor triangle. For a valid edge coordinate, a + b + c should equal 1.
TriEdgeDirection	direction	The TriEdgeDirection indicating which of the three sides of the anchor triangle this edge occupies.

Fields

A

The A lane value of the downward anchor triangle.

Declaration

public readonly int A

Field Value

Type	Description
int

B

The B lane value of the downward anchor triangle.

Declaration

public readonly int B

Field Value

Type	Description
int

C

The C lane value of the downward anchor triangle. For a valid edge, A + B + C must equal 1 (downward triangle sum).

Declaration

public readonly int C

Field Value

Type	Description
int

Direction

The direction of this edge relative to the anchor downward triangle, indicating which lane axis the shared boundary lies along.

Declaration

public readonly TriEdgeDirection Direction

Field Value

Type	Description
TriEdgeDirection

See Also

TriEdgeDirection

Properties

IsValid

Gets a value indicating whether the anchor triangle portion of this coordinate is valid - that is, whether A + B + C = 1 (a downward triangle).

Declaration

public bool IsValid { get; }

Property Value

Type	Description
bool	true when the sum of the three lane values equals 1; false if the coordinate was constructed with inconsistent lane values that do not represent any real downward triangle.

Methods

Equals(TriEdgeCoord)

Determines whether this edge coordinate equals another edge coordinate.

Declaration

public bool Equals(TriEdgeCoord other)

Parameters

Type	Name	Description
TriEdgeCoord	other	The edge coordinate to compare with.

Returns

Type	Description
bool	True if all fields are equal.

Equals(object)

Determines whether this edge coordinate equals another object.

Declaration

public override bool Equals(object obj)

Parameters

Type	Name	Description
object	obj	The object to compare with.

Returns

Type	Description
bool	True if the object is a TriEdgeCoord with equal values.

Overrides

ValueType.Equals(object)

GetCellsNonAlloc(TriEdgeCoord, Span<TriCoord>)

Writes the two triangle cells that share this edge into the provided buffer without allocating.

Declaration

public static int GetCellsNonAlloc(TriEdgeCoord edge, Span<TriCoord> buffer)

Parameters

Type	Name	Description
TriEdgeCoord	edge	The canonical edge coordinate whose adjacent cells are needed.
Span<TriCoord>	buffer	A span of at least 2 elements to receive the two adjacent TriCoord values.

Returns

Type	Description
int	The number of cells written - always 2 when buffer has at least 2 elements; 0 if the buffer is too small.

Remarks

The first element written is always the downward anchor triangle (edge.A, edge.B, edge.C). The second element is the upward neighbor:

• A: upward (a+1, b, c).
• B: upward (a, b+1, c).
• C: upward (a, b, c+1).

GetCornersNonAlloc(TriEdgeCoord, Span<TriCornerCoord>)

Writes the two corner vertices that are the endpoints of this edge into the provided buffer without allocating.

Declaration

public static int GetCornersNonAlloc(TriEdgeCoord edge, Span<TriCornerCoord> buffer)

Parameters

Type	Name	Description
TriEdgeCoord	edge	The canonical edge coordinate whose corner endpoints are needed.
Span<TriCornerCoord>	buffer	A span of at least 2 elements to receive the two TriCornerCoord endpoints.

Returns

Type	Description
int	The number of corners written - always 2 when buffer has at least 2 elements; 0 if the buffer is too small.

Remarks

Every edge endpoint is a Type I corner (A + B + C = 0 on the TriCornerCoord sublattice), meaning it is adjacent to three downward triangles. The endpoint pairs by direction are:

• A: corners (a, b, c-1) and (a, b-1, c).
• B: corners (a-1, b, c) and (a, b, c-1).
• C: corners (a, b-1, c) and (a-1, b, c).

GetEdgesOfCellNonAlloc(TriCoord, Span<TriEdgeCoord>)

Writes the three canonical edge coordinates of a triangle cell into the provided buffer without allocating.

Declaration

public static int GetEdgesOfCellNonAlloc(TriCoord cell, Span<TriEdgeCoord> buffer)

Parameters

Type	Name	Description
TriCoord	cell	The triangle coordinate whose edges are requested.
Span<TriEdgeCoord>	buffer	A span of at least 3 elements to receive the three TriEdgeCoord values.

Returns

Type	Description
int	The number of edges written - 3 when buffer has enough space and cell is a valid triangle; 0 otherwise.

Remarks

Each triangle has exactly three edges. Because the canonical form always uses a downward triangle as the anchor, the edges are expressed differently depending on the orientation of cell:

• Downward (A + B + C = 1): the cell is the anchor for all three edges - (a,b,c,A), (a,b,c,B), (a,b,c,C).
• Upward (A + B + C = 2): the neighboring downward triangles are the anchors - (a-1,b,c,A), (a,b-1,c,B), (a,b,c-1,C).

If cell has a lane sum other than 1 or 2 the coordinate is not a valid triangle and 0 is returned.

GetHashCode()

Returns a hash code for this edge coordinate.

Declaration

public override int GetHashCode()

Returns

Type	Description
int	A hash code based on A, B, C, and direction.

Overrides

ValueType.GetHashCode()

ToString()

Returns a human-readable string representation of this edge coordinate.

Declaration

public override string ToString()

Returns

Type	Description
string	A string in the format (A, B, C, Direction), for example (1, 1, -1, A).

Overrides

ValueType.ToString()

Operators

operator ==(TriEdgeCoord, TriEdgeCoord)

Returns true when left and right have identical anchor lane values and direction.

Declaration

public static bool operator ==(TriEdgeCoord left, TriEdgeCoord right)

Parameters

Type	Name	Description
TriEdgeCoord	left	The left operand.
TriEdgeCoord	right	The right operand.

Returns

Type	Description
bool	true if both edge coordinates are equal; otherwise false.

operator !=(TriEdgeCoord, TriEdgeCoord)

Returns true when left and right differ in at least one field.

Declaration

public static bool operator !=(TriEdgeCoord left, TriEdgeCoord right)

Parameters

Type	Name	Description
TriEdgeCoord	left	The left operand.
TriEdgeCoord	right	The right operand.

Returns

Type	Description
bool	true if the edge coordinates are not equal; otherwise false.

Implements

IEquatable<T>

See Also

TriCoord

TriEdgeDirection

TriCornerCoord

TriEdgeMap<TData>