94 lines
3.5 KiB
Markdown
94 lines
3.5 KiB
Markdown
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---
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title: "NarrowPhase"
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date: 2019-09-15T11:19:13-07:00
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weight: 20
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---
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*NarrowPhase* is a static class containing methods for narrow-phase collision detection.
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Note that all the **TestCollision** overloads automatically employ fast path checks.
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## Methods
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##### **public static bool TestCollision(IShape2D shapeA, Transform2D transformA, IShape2D shapeB, Transform2D transformB)**
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Tests if the two shape-transform pairs are overlapping.
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**Example:**
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```cs
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var circleA = new Circle(2);
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var transformA = new Transform2D(new Vector2(-1, -1));
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var circleB = new Circle(2);
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var transformB = new Transform2D(new Vector2(1, 1));
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var result = GJK2D.TestCollision(circleA, transformA, circleB, transformB);
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```
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In this example, these transformed circles are indeed overlapping, so *result* will be true.
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---
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##### **public static bool TestCollision(IHasAABB2D hasBoundingBoxA, Transform2D transformA, IHasAABB2D hasBoundingBoxB, Transform2D transformB)**
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Detects whether two AABB-transform pairs are overlapping.
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---
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##### **public static bool TestCollision(MultiShape multiShape, Transform2D multiShapeTransform, IShape2D shape, Transform2D shapeTransform)**
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Tests if a multishape-transform and shape-transform pair are overlapping.
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---
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##### **public static bool TestCollision(IShape2D shape, Transform2D shapeTransform, MultiShape multiShape, Transform2D multiShapeTransform)**
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Tests if a multishape-transform and shape-transform pair are overlapping.
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---
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##### **public static bool TestCollision(MultiShape multiShapeA, Transform2D transformA, MultiShape multiShapeB, Transform2D transformB)**
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Tests if two multishape-transform pairs are overlapping.
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---
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##### **public static bool TestRectangleOverlap(Rectangle rectangleA, Transform2D transformA, Rectangle rectangleB, Transform2D transformB)**
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Fast path for axis-aligned rectangles. Assumes that the transforms have zero rotation. If the transforms have non-zero rotation this will be inaccurate.
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---
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##### **public static bool TestPointRectangleOverlap(Point point, Transform2D pointTransform, Rectangle rectangle, Transform2D rectangleTransform)**
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Fast path for overlapping point and axis-aligned rectangle. The rectangle transform must have non-zero rotation.
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---
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##### **public static bool TestCircleOverlap(Circle circleA, Transform2D transformA, Circle circleB, Transform2D transformB)**
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Fast path for overlapping circles. The circles must have uniform scaling.
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---
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##### **public static (bool, Simplex) FindCollisionSimplex(IShape2D shapeA, Transform2D transformA, IShape2D shapeB, Transform2D transformB)**
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Tests if the two shape-transform pairs are overlapping, and if so returns a Simplex that can be used by the EPA algorithm to determine a minimum separating vector.
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**Example:**
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```cs
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var circleA = new Circle(2);
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var transformA = new Transform2D(new Vector2(-1, -1));
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var circleB = new Circle(2);
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var transformB = new Transform2D(new Vector2(1, 1));
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var (result, simplex) = GJK2D.TestCollision(circleA, transformA, circleB, transformB);
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```
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In this example, these transformed circles are indeed overlapping, so *result* will be true and *simplex* will contain the Simplex that can be used by EPA to determine a minimum separating vector.
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---
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##### **public unsafe static Vector2 Intersect(IShape2D shapeA, Transform2D Transform2DA, IShape2D shapeB, Transform2D Transform2DB, Simplex2D simplex)**
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Returns a minimum separating vector in the direction from A to B. This information can be used to push two overlapping shape-transforms apart.
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