Cast rays to intersect with mesh

Usage

vcg_raycaster(
  x,
  ray_origin,
  ray_direction,
  max_distance = Inf,
  both_sides = FALSE
)

Arguments

x: surface mesh
ray_origin: a matrix with 3 rows or a vector of length 3, the positions of ray origin
ray_direction: a matrix with 3 rows or a vector of length 3, the direction of the ray, will be normalized to length 1
max_distance: positive maximum distance to cast the normalized ray; default is infinity. Any invalid distances (negative, zero, or NA) will be interpreted as unset.
both_sides: whether to inverse the ray (search both positive and negative ray directions); default is false

Value

A list of ray casting results: whether any intersection is found, position and face normal of the intersection, distance of the ray, and the index of the intersecting face (counted from 1)

Coercing Surface Inputs

The surface objects are converted to 'mesh3d' object before applying further calculations.

When surface is a surface ieegio object, the returned mesh3d$vb contains vertices that have been left-multiplied by surface$geometry$transforms[[1]] (the first transform stored in the geometry, typically the ScannerAnat or voxel-to-world transform).

Breaking change: Earlier versions (before 0.2.6) of ravetools returned the raw surface$geometry$vertices without applying any transform, so downstream code often multiplied by surface$geometry$transforms[[1]] (or an equivalent) manually before working in world space. Such code will now double apply the transform and produce incorrect coordinates. If you previously applied a transform from surface$geometry$transforms by hand after calling a ravetools mesh function on an 'ieegio_surface', remove that manual step.

Surfaces with an empty or missing geometry$transforms list (for example, surfaces produced by ieegio's volume_to_surface, which stores an identity transform) are unaffected.

If geometry$transforms contains multiple transforms targeting different coordinate spaces, only the first one is used. Callers that need a specific target space should select and apply that transform themselves before calling ravetools mesh functions.

Examples


library(ravetools)
sphere <- vcg_sphere(normals = FALSE)
sphere$vb[1:3, ] <- sphere$vb[1:3, ] + c(10, 10, 10)
vcg_raycaster(
  x = sphere,
  ray_origin = array(c(0, 0, 0, 1, 0, 0), c(3, 2)),
  ray_direction = c(1, 1, 1)
)
#> $has_intersection
#> [1] TRUE TRUE
#> 
#> $intersection
#>          [,1]      [,2]
#> [1,] 9.425265 10.336223
#> [2,] 9.425265  9.336223
#> [3,] 9.425265  9.336223
#> 
#> $normals
#>            [,1]       [,2]
#> [1,] -0.5773502  0.3685302
#> [2,] -0.5773502 -0.6649041
#> [3,] -0.5773503 -0.6496830
#> 
#> $face_index
#> [1] 1217 1179
#> 
#> $distance
#> [1] 16.32504 16.17081
#> 
#> $ray_origin
#>      [,1] [,2]
#> [1,]    0    1
#> [2,]    0    0
#> [3,]    0    0
#> 
#> $ray_direction
#>           [,1]      [,2]
#> [1,] 0.5773503 0.5773503
#> [2,] 0.5773503 0.5773503
#> [3,] 0.5773503 0.5773503
#>