Name

---

    RAY_INTERSECTS_FACET

Purpose

---

    This function determines whether a given ray (or set of rays)
    intersect a provided triangular facet in 3-space.

Category

---

    Graphics.

Calling Sequence

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    Result = RAY_INTERSECTS_FACET( rayOrigin,
                                  rayDirection,
                                  facet,
                                  INTERSECTION_POINT=intersectionPoint,
                                  INTERSECTION_DISTANCE=intersectionDistance,
                                  INTERSECTION_ANGLE=intersectionAngle )

Inputs

---

    rayOrigin
      A 3-element vector -OR- a 3xN element array containing the origin (or
      origins) of the cast ray(s)
    rayDirection
      A complementary 3-element vector -OR- 3xN element array containing the
      direction vector (or direction vectors) for each of the ray origins
      described by rayOrigin
    facet
      A structure containing the vertices of a triangular facet - the tags
      are POINT1, POINT2, and POINT3 and these represent the 3-dimensional
      coordinates, defined as a 3-element vector, for the vertices in
      counter-clockwise order so that the right-hand rule holds for defining
      the surface normal

Keyword Parameters

---

    INTERSECTION_POINT
      A named variable that upon completion of the routine will contain a
      3-element vector -OR- 3xN element array of ray-plane intersection
      point(s)
    INTERSECTION_DISTANCE
      A named variable that upon completion of the routine will contain a
      scalar -OR- N-element vector of intersection distance(s) along each ray-
      facet path
    INTERSECTION_ANGLE
      A named variable that upon completion of the routine will contain a
      scalar -OR- N-element vector of intersection angle(s) that the ray(s)
      make with the interesected plane
    NOTE: These keyword parameters will contain the values noted above even if
          the ray did not intersect the plane within the triangular boundaries
   

Result

---

    A boolean status flag (or vector of flags) indicating whether the provided
    ray (or set of rays) intersect the triangular facet specified; 1 indicates
    the intersection (or hit) occurred, 0 indicates that it did not. The criteria
    for the hit are
      1) the ray intersects the plane inside the triangular boundary
      2) the ray intersects the plane on the same side as the surface normal

Side Effects

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    None

Requires

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    ANGLE_BETWEEN_TWO_VECTORS
    DOT_PRODUCT
    FACET_VERTICES_TO_PLANE_COEFFICIENTS
    NORMALIZE
    POINT_INSIDE_TRIANGULAR_FACET
    REPLICATE_VECTOR

Modification History

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    Written by: Carl Salvaggio
    September, 2009 Original code
 

Disclaimer

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    This source code is provided "as is" and without warranties as to performance
    or merchantability. The author and/or distributors of this source code may
    have made statements about this source code. Any such statements do not
    constitute warranties and shall not be relied on by the user in deciding
    whether to use this source code.
    This source code is provided without any express or implied warranties
    whatsoever. Because of the diversity of conditions and hardware under which
    this source code may be used, no warranty of fitness for a particular purpose
    is offered. The user is advised to test the source code thoroughly before
    relying on it. The user must assume the entire risk of using the source code.