Class CollisionChecker

Helper methods for detecting collisions in joint movements.

Collision checks work by tracking the movements of all edges in the system. Edges are created by all bonds and expanded, expanding and contracting particles in the system, as well as the boundaries of objects. If any two edges that do not coincide in one point at the start or the end of the movement intersect during the movement, a collision occurs.

Inheritance

object

CollisionChecker

Namespace: AS2.Sim

Assembly: .dll

Syntax

public static class CollisionChecker

Fields

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debugDisplayTime

The number of seconds for which the collision visualization should be displayed.

Declaration

public static float debugDisplayTime

Field Value

Type	Description
float

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debugLines

The debug lines drawn for the last detected collision.

Declaration

private static List<CollisionChecker.DebugLine> debugLines

Field Value

Type	Description
List<CollisionChecker.DebugLine>

Methods

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ComputeOrientationTwoSegments(Vector2Int, Vector2Int, Vector2Int)

Calculates the orientation of the triangle formed by the three given points.

The orientation can be counter-clockwise, clockwise or collinear.

Declaration

public static int ComputeOrientationTwoSegments(Vector2Int p1, Vector2Int p2, Vector2Int p3)

Parameters

Type	Name	Description
Vector2Int	p1	The first point.
Vector2Int	p2	The second point.
Vector2Int	p3	The third point.

Returns

Type	Description
int	`1` if the orientation is clockwise, `-1` if it is counter-clockwise and `0` if it is collinear.

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DrawDebugLine(DebugLine, float)

Helper for drawing debug lines.

Declaration

private static void DrawDebugLine(CollisionChecker.DebugLine line, float time = -1)

Parameters

Type	Name	Description
CollisionChecker.DebugLine	line	The line to be drawn.
float	time	The time for which the line should be displayed. Negative values lead to debugDisplayTime being used.

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DrawDebugLine(Vector2Int, Vector2Int, Color, bool, float)

Helper for drawing debug lines.

Declaration

private static void DrawDebugLine(Vector2Int p, Vector2Int q, Color color, bool arrow = false, float time = -1)

Parameters

Type	Name	Description
Vector2Int	p	The start point of the line.
Vector2Int	q	The end point of the line.
Color	color	The color of the line.
bool	arrow	Determines whether the line should have an arrow.
float	time	The time for which the line should be displayed. Negative values lead to debugDisplayTime being used.

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DrawDebugLines(DebugLine[], float)

Draws the given debug lines onto the screen.

Note that this only works in the Unity Editor and the "Gizmos" toggle in the Game View must be activated for the lines to be visible.

Declaration

public static void DrawDebugLines(CollisionChecker.DebugLine[] lines, float time = -1)

Parameters

Type	Name	Description
DebugLine[]	lines	The lines to be drawn. Should be the return value of GetDebugLines().
float	time	The time in seconds for which the lines should be displayed. A negative value will lead to debugDisplayTime being used.

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EdgesCollide(EdgeMovement, EdgeMovement)

Checks if the two given edge movements collide. This is the most general of the collision check methods. It selects the most appropriate helper procedure to apply to the two edges.

Declaration

public static bool EdgesCollide(EdgeMovement em1, EdgeMovement em2)

Parameters

Type	Name	Description
EdgeMovement	em1	The first edge movement.
EdgeMovement	em2	The second edge movement.

Returns

Type	Description
bool	`true` if and only if the two edges collide.

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EdgesCollideBothNonStatic(EdgeMovement, EdgeMovement)

Checks if the two given edges collide, where both edges can be contraction or expansion movements.

Declaration

public static bool EdgesCollideBothNonStatic(EdgeMovement em1, EdgeMovement em2)

Parameters

Type	Name	Description
EdgeMovement	em1	The first edge movement.
EdgeMovement	em2	The second edge movement.

Returns

Type	Description
bool	`true` if and only if the two given edges collide.

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EdgesCollideOneStatic(EdgeMovement, EdgeMovement)

Checks if the two given edges collide, given that the first edge is not a contraction or expansion.

Declaration

public static bool EdgesCollideOneStatic(EdgeMovement emStatic, EdgeMovement emOther)

Parameters

Type	Name	Description
EdgeMovement	emStatic	The edge movement that is not a contraction or expansion.
EdgeMovement	emOther	The other edge movement, which might be a contraction or expansion.

Returns

Type	Description
bool	`true` if and only if the two edges collide.

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GenerateDebugLines(EdgeMovement, bool)

Helper that generates lines and arrows showing the absolute trajectory of an EdgeMovement.

The generated movements are added to debugLines.

Declaration

private static void GenerateDebugLines(EdgeMovement em, bool pov)

Parameters

Type	Name	Description
EdgeMovement	em	The movement to draw.
bool	pov

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GetDebugLines()

Returns the list of debug lines generated for the last detected collision. These lines can be used to display where the collision was detected.

Declaration

public static CollisionChecker.DebugLine[] GetDebugLines()

Returns

Type	Description
DebugLine[]	An array containing information for drawing lines that show where the last collision was detected.

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HaveSharedNode(EdgeMovement, EdgeMovement)

Checks whether the two given edge movements share an end point at the start or the end of the movement.

Declaration

public static bool HaveSharedNode(EdgeMovement em1, EdgeMovement em2)

Parameters

Type	Name	Description
EdgeMovement	em1	The first edge movement.
EdgeMovement	em2	The second edge movement.

Returns

Type	Description
bool	`true` if and only if the two given edge movements share an end point at the start or the end of the movement.

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LineSegmentsIntersect(Vector2Int, Vector2Int, Vector2Int, Vector2Int)

Checks if the two given two-dimensional line segments intersect.

Uses the algorithm described in https://www.dcs.gla.ac.uk/~pat/52233/slides/Geometry1x1.pdf.

Declaration

public static bool LineSegmentsIntersect(Vector2Int p1, Vector2Int q1, Vector2Int p2, Vector2Int q2)

Parameters

Type	Name	Description
Vector2Int	p1	The start point of the first segment.
Vector2Int	q1	The end point of the first segment.
Vector2Int	p2	The start point of the second segment.
Vector2Int	q2	The end point of the second segment.

Returns

Type	Description
bool	`true` if and only if the two segments intersect.

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SegmentsIntersect1D(float, float, float, float)

Checks if the two given one-dimensional line segments intersect.

Declaration

public static bool SegmentsIntersect1D(float p1, float q1, float p2, float q2)

Parameters

Type	Name	Description
float	p1	The start of the first segment.
float	q1	The end of the first segment.
float	p2	The start of the second segment.
float	q2	The end of the second segment.

Returns

Type	Description
bool	`true` if and only if the two segments intersect.