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ray_triangle_intersect

ray_triangle_intersect(origin, dir, v0, v1, v2, return_negative=False)

Find if and where a straight line intersects a triangle in 3D

Parameters:

Name Type Description Default
origin (dim,) numpy double array

Ray origin position coordinates

 required
dir (dim,) numpy double array

Ray origin direction coordinates

 required
v0 (dim,) numpy double array

First triangle vertex coordinates

 required
v1 (dim,) numpy double array

Second triangle vertex coordinates

 required
v2 (dim,) numpy double array

Third triangle vertex coordinates

 required
return_negative bool, optional (default False)

Whether to return intersections at negative time (i.e., "behind" the ray)

 False

Returns:

Name Type Description
t double

"Time" it takes the ray to hit the triangle (may be negative)
is_hit bool

Whether the ray ever hits the triangle
hit_coord (dim,) numpy double array

Intersection coordinates. Some entries of this vector will be infinite if is_hit is False.

See Also

ray_polyline_intersect, ray_mesh_intersect.

Notes

Uses the Möller–Trumbore ray-triangle intersection algorithm.

Examples:

from gpytoolbox import ray_triangle_intersect
# Random origin and direction
origin = np.random.rand(3)
dir = np.random.rand(3)
# Random vertices
V = np.random.rand(3,3)
v1 = V[0,:]
v2 = V[1,:]
v3 = V[2,:]
t,is_hit,hit_coord = ray_triangle_intersect(origin,dir,v1,v2,v3)
Source code in src/gpytoolbox/ray_triangle_intersect.py 
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def ray_triangle_intersect(origin,dir, v0, v1, v2, return_negative=False):
    """Find if and where a straight line intersects a triangle in 3D

    Parameters
    ----------
    origin : (dim,) numpy double array
        Ray origin position coordinates
    dir : (dim,) numpy double array
        Ray origin direction coordinates
    v0 : (dim,) numpy double array
        First triangle vertex coordinates
    v1 : (dim,) numpy double array
        Second triangle vertex coordinates
    v2 : (dim,) numpy double array
        Third triangle vertex coordinates
    return_negative : bool, optional (default False)
        Whether to return intersections at negative time (i.e., "behind" the ray)

    Returns
    -------
    t : double
        "Time" it takes the ray to hit the triangle (may be negative)
    is_hit : bool
        Whether the ray ever hits the triangle
    hit_coord : (dim,) numpy double array
        Intersection coordinates. Some entries of this vector will be infinite if is_hit is False.

    See Also
    --------
    ray_polyline_intersect, ray_mesh_intersect.

    Notes
    -----
    Uses the Möller–Trumbore ray-triangle intersection algorithm.

    Examples
    --------
    ```python
    from gpytoolbox import ray_triangle_intersect
    # Random origin and direction
    origin = np.random.rand(3)
    dir = np.random.rand(3)
    # Random vertices
    V = np.random.rand(3,3)
    v1 = V[0,:]
    v2 = V[1,:]
    v3 = V[2,:]
    t,is_hit,hit_coord = ray_triangle_intersect(origin,dir,v1,v2,v3)
    ```
    """
    v0 = np.ravel(v0)
    v1 = np.ravel(v1)
    v2 = np.ravel(v2)

    v0v1 = v1 - v0
    v0v2 = v2 - v0
    pvec = np.cross(dir,v0v2)
    det = np.dot(v0v1,pvec)

    if (np.abs(det) < 1e-6):
        t =  np.Inf
        hit = np.Inf*np.ones(3)
        is_hit = False
        return t,is_hit, hit

    invDet = 1.0 / det
    tvec = origin - v0
    u = np.dot(tvec,pvec) * invDet

    if (u < 0 or u > 1):
        t =  np.Inf
        hit = np.Inf*np.ones(3)
        is_hit = False
        return t,is_hit, hit

    qvec = np.cross(tvec,v0v1)
    v = np.dot(dir,qvec)*invDet

    if ((v < 0) or ((u + v) > 1)):
        t =  np.Inf
        hit = np.Inf*np.ones(3)
        is_hit = False
        return t,is_hit, hit

    t = np.dot(v0v2,qvec)*invDet
    hit = origin + t*dir
    is_hit = True
    if (not return_negative):
        if(t<0):
            t =  np.Inf
            hit = np.Inf*np.ones(3)
            is_hit = False
    return t,is_hit, hit