Detailed Description

Stores the mathematical object of a ray that begins at an origin (a 3D point) and points in a direction (a unit 3D vector).

Rays can intersect a variety of other computer graphics objects, such as planes, triangles, spheres, 3D meshes, etc. These intersections can be tested with the Intersect...() methods. The Ray can also be transformed by a Matrix4. Example:

// Create a pick ray from the mouse position
void MyGraphicsApp::OnLeftMouseDown(const Point2 &pos) {
   Point2 mouse_xy = PixelsToNormalizedDeviceCoords(pos);
   float mouse_z = ReadZValueAtPixel(pos);
   Point3 mouse_3d = GfxMath::ScreenToNearPlane(view_matrix, proj_matrix, mouse_xy, mouse_z);
   Matrix4 camera_matrix = view_matrix.Inverse();
   Point3 eye = camera_matrix.ColumnToPoint3(3);
 
   Ray pick_ray(eye, mouse_3d - eye);
 
   // check to see if the ray intersects a sphere
   float t;
   Point3 p;
   if (pick_ray.IntersectSphere(Point3(0,0,0), 2.0, &t, &p)) {
       std::cout << "Mouse pointing at sphere!  Intersection point = " << p << std::endl;
   }
}

Definition at line 54 of file ray.h.

#include <ray.h>

Public Member Functions
	Ray ()
	Defaults to a ray at the origin and pointing in the -Z direction. More...

	Ray (const Point3 &origin, const Vector3 &direction)
	Creates a ray from a 3D origin and direction. More...

virtual	~Ray ()
	Ray destructor. More...

bool	operator== (const Ray &other) const
	Check for "equality", taking floating point imprecision into account. More...

bool	operator!= (const Ray &other) const
	Check for "inequality", taking floating point imprecision into account. More...

float	Length () const
	Returns the length of the direction vector. More...

bool	IntersectPlane (const Point3 &planePt, const Vector3 &planeNormal, float iTime, Point3 iPoint) const
	Checks to see if the ray intersects a plane defined by a point and a normal. More...

bool	IntersectTriangle (const Point3 &v1, const Point3 &v2, const Point3 &v3, float iTime, Point3 iPoint) const
	Checks to see if the ray intersects a triangle defined by the vertices v1, v2, and v3. More...

bool	IntersectQuad (const Point3 &v1, const Point3 &v2, const Point3 &v3, const Point3 &v4, float iTime, Point3 iPoint) const
	Checks to see if the ray intersects a quad defined by the vertices v1, v2, v3, and v4. More...

bool	IntersectSphere (const Point3 &center, float radius, float iTime, Point3 iPoint) const
	Checks to see if the ray intersects a sphere defined by a center point and a radius. More...

bool	IntersectMesh (const Mesh &mesh, float iTime, Point3 iPoint, int *iTriangleID) const
	Checks to see if the ray intersects a triangle mesh. More...

bool	FastIntersectMesh (Mesh mesh, float iTime, Point3 iPoint, int iTriangleID) const
	Checks to see if the ray intersects a triangle mesh. More...

bool	IntersectAABB (const AABB &box, float *iTime) const
	Checks to see if the ray intersects an AABB (Axis-Aligned Bounding Box). More...

Point3	origin () const
	Returns the origin. More...

Vector3	direction () const
	Returns the direction. More...

void	set (Point3 newOrigin, Vector3 newDir)
	Sets a new origin and direction. More...

Constructor & Destructor Documentation

◆ Ray() [1/2]

mingfx::Ray::Ray ( )

Defaults to a ray at the origin and pointing in the -Z direction.

◆ Ray() [2/2]

mingfx::Ray::Ray	(	const Point3 &	origin,
		const Vector3 &	direction
	)

Creates a ray from a 3D origin and direction.

◆ ~Ray()

virtual mingfx::Ray::~Ray ( )

virtual

Ray destructor.

Member Function Documentation

◆ direction()

Vector3 mingfx::Ray::direction ( ) const

Returns the direction.

◆ FastIntersectMesh()

bool mingfx::Ray::FastIntersectMesh	(	Mesh *	mesh,
		float *	iTime,
		Point3 *	iPoint,
		int *	iTriangleID
	)		const

Checks to see if the ray intersects a triangle mesh.

This uses a BVH (Bounding Volume Hierarchy) to accelerate the ray-triangle intersection tests. Each mesh can optionally store a BVH. If a BVH has already been calculated for the mesh (done with Mesh::CalculateBVH()), then this function will be much faster than the brute-force IntersectMesh() function. If a BVH has not already been calculated for the mesh, the first call to FastIntersectMesh() will trigger the mesh to create a BVH (not a fast operation) but then subsequent calls to FastIntersectMesh() will be fast.

◆ IntersectAABB()

bool mingfx::Ray::IntersectAABB	(	const AABB &	box,
		float *	iTime
	)		const

Checks to see if the ray intersects an AABB (Axis-Aligned Bounding Box).

Typically, this is the first step of a more detailed intersection test and we don't care about the actual point of intersection, just whether it intersects or not. So, we don't bother calculating the iPoint. We get the iTime for free though, so we do return that. You can calc the iPoint if you want using:

float t;
if (ray.IntersectAABB(box, &t)) {
  Point3 iPoint = ray.origin() + t*ray.direction();
}

◆ IntersectMesh()

bool mingfx::Ray::IntersectMesh	(	const Mesh &	mesh,
		float *	iTime,
		Point3 *	iPoint,
		int *	iTriangleID
	)		const

Checks to see if the ray intersects a triangle mesh.

This is a brute-force check over each triangle in the mesh. If there was an intersection, true is returned, iTime is set to the intersection time, iPoint is set to the intersection point, and iTriangleID is set to the ID of the closest intersected triangle along the ray.

◆ IntersectPlane()

bool mingfx::Ray::IntersectPlane	(	const Point3 &	planePt,
		const Vector3 &	planeNormal,
		float *	iTime,
		Point3 *	iPoint
	)		const

Checks to see if the ray intersects a plane defined by a point and a normal.

If there was an intersection, true is returned, iTime is set to the intersection time, and iPoint is set to the intersection point. The plane is considered to be 1-sided. That is the intersection will only occur if the ray hits the plane from its front side as determined by the plane's normal.

◆ IntersectQuad()

bool mingfx::Ray::IntersectQuad	(	const Point3 &	v1,
		const Point3 &	v2,
		const Point3 &	v3,
		const Point3 &	v4,
		float *	iTime,
		Point3 *	iPoint
	)		const

Checks to see if the ray intersects a quad defined by the vertices v1, v2, v3, and v4.

The vertices must be provided in counter-clockwise order so that the normal of the triangle can be determined via the right-hand rule. The intersection will only happen if the ray hits the front side of the triangle. If there was an intersection, true is returned, iTime is set to the intersection time, and iPoint is set to the intersection point.

◆ IntersectSphere()

bool mingfx::Ray::IntersectSphere	(	const Point3 &	center,
		float	radius,
		float *	iTime,
		Point3 *	iPoint
	)		const

Checks to see if the ray intersects a sphere defined by a center point and a radius.

If there was an intersection, true is returned, iTime is set to the intersection time, and iPoint is set to the intersection point.

◆ IntersectTriangle()

bool mingfx::Ray::IntersectTriangle	(	const Point3 &	v1,
		const Point3 &	v2,
		const Point3 &	v3,
		float *	iTime,
		Point3 *	iPoint
	)		const

Checks to see if the ray intersects a triangle defined by the vertices v1, v2, and v3.

The vertices must be provided in counter-clockwise order so that the normal of the triangle can be determined via the right-hand rule. The intersection will only happen if the ray hits the front side of the triangle. If there was an intersection, true is returned, iTime is set to the intersection time, and iPoint is set to the intersection point.

◆ Length()

float mingfx::Ray::Length ( ) const

Returns the length of the direction vector.

◆ operator!=()

bool mingfx::Ray::operator!= ( const Ray & other ) const

Check for "inequality", taking floating point imprecision into account.

◆ operator==()

bool mingfx::Ray::operator== ( const Ray & other ) const

Check for "equality", taking floating point imprecision into account.

◆ origin()

Point3 mingfx::Ray::origin ( ) const

Returns the origin.

◆ set()

void mingfx::Ray::set	(	Point3	newOrigin,
		Vector3	newDir
	)

Sets a new origin and direction.

The documentation for this class was generated from the following file:

src/ray.h