Collision detection

Getting Started for DX11	Getting Started for DX12

This lesson covers simple collision detection using rectangles, spheres, and boxes.

2D collision detection

The primary functionality here offered by the DirectX Tool Kit is in SimpleMath's Rectangle class:

The Contains methods perform rectangle contains point and rectangle contains rectangle tests.

bool Contains(long ix, long iy) const;
bool Contains(const Vector2& point) const;
bool Contains(const Rectangle& r) const;
bool Contains(const RECT& rct) const;

The Intersects methods perform rectangle/rectangle intersection tests.

bool Intersects(const Rectangle& r) const;
bool Intersects(const RECT& rct) const;
static Rectangle Intersect(const Rectangle& ra, const Rectangle& rb);
static RECT Intersect(const RECT& rcta, const RECT& rctb);

The Inflate and Union methods can be useful for adjusting collision rectangles.

void Inflate(long horizAmount, long vertAmount);
static Rectangle Union(const Rectangle& ra, const Rectangle& rb);
static RECT Union(const RECT& rcta, const RECT& rctb);

3D collision detection

For 3D collision implementation, the DirectXMath bounding classes provide implementations of many 3D test. If desired, you can interop with these using SimpleMath's types like Vector3, Vector4, Plane, Ray, etc.

See the Collision (PC / UWP / GDK / XDK) sample for a demonstration of these DirectXCollision.h types.

BoundingSphere class

This is the classic 'bounding sphere' collision primitive.

The Contains method provides sphere contains point, sphere contains triangle, sphere contains sphere, sphere contains box, and sphere contains frustum tests.

ContainmentType Contains(XMVECTOR Point) const;
ContainmentType Contains(XMVECTOR V0, XMVECTOR V1, XMVECTOR V2) const;
ContainmentType Contains(const BoundingSphere& sh) const;
ContainmentType Contains(const BoundingBox& box) const;
ContainmentType Contains(const BoundingOrientedBox& box) const;
ContainmentType Contains(const BoundingFrustum& fr) const;

The ContainedBy method provides sphere contained by frustum test.

ContainmentType ContainedBy(XMVECTOR Plane0, XMVECTOR Plane1, XMVECTOR Plane2,
    XMVECTOR Plane3, XMVECTOR Plane4, XMVECTOR Plane5) const;

The Intersects method provides sphere/sphere, sphere/box, sphere/frustum, sphere/triangle, sphere/plane, and ray/sphere intersection tests.

bool Intersects(const BoundingSphere& sh) const;
bool Intersects(const BoundingBox& box) const;
bool Intersects(const BoundingOrientedBox& box) const;
bool Intersects(const BoundingFrustum& fr) const;
bool Intersects(XMVECTOR V0, XMVECTOR V1, XMVECTOR V2) const;
PlaneIntersectionType Intersects(XMVECTOR Plane) const;
bool Intersects(XMVECTOR Origin, XMVECTOR Direction, float& Dist) const;

See Microsoft Docs.

BoundingBox class

This is an 'axis-aligned bounding box' collision primitive.

The Contains method provides box contains point, box contains triangle, box contains sphere, box contains box, and box contains frustum tests.

The ContainedBy method provides box contained by frustum test.

The Intersects method provides box/box, box/sphere, box/frustum, box/triangle, box/plane and ray/box intersection tests.

See Microsoft Docs.

BoundingOrientedBox class

This is an 'oriented bounding box' collision primitive. It provides the same Contains, ContainedBy, and Intersects methods as the axis-aligned bounding box.

See Microsoft Docs.

BoundingFrustum class

This is a 'view frustum' collision primitive.

The Contains method provides frustum contains point, frustum contains triangle, frustum contains sphere, frustum contains box, and frustum contains frustum tests.

The Intersects method provides frustum/sphere, frustum/box, frustum/frustum, frustum/triangle, frustum/plane, and ray/frustum intersection tests.

See MicrosoftDocs.

Note: The BoundingFrustum class's CreateFromMatrix function assumed Left-Handed coordinates. In DirectXMath 3.16 or later, there's a defaulted parameter you can use for Right-Handed projection matrices: BoundingFrustum::CreateFromMatrix(fr, matrix, true);

TriangleTests namespace

This namespace provides a number of triangle tests not covered by the other bounding classes.

These Intersects functions cover ray/triangle, triangle/triangle, and plane/triangle tests.

bool Intersects(XMVECTOR Origin, XMVECTOR Direction,
    XMVECTOR V0, XMVECTOR V1, XMVECTOR V2, float& Dist);
bool Intersects(XMVECTOR A0, XMVECTOR A1, XMVECTOR A2,
    XMVECTOR B0, XMVECTOR B1, XMVECTOR B2);
PlaneIntersectionType Intersects(XMVECTOR V0, XMVECTOR V1, XMVECTOR V2, XMVECTOR Plane);

The ContainedBy function covers frustum contains triangle.

ContainmentType ContainedBy(XMVECTOR V0, XMVECTOR V1, XMVECTOR V2,
    XMVECTOR Plane0, XMVECTOR Plane1, XMVECTOR Plane2,
    XMVECTOR Plane3, XMVECTOR Plane4, XMVECTOR Plane5);

See Microsoft Docs.

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