ravetools (version 0.3.2)

vcg_raycaster: Cast rays to intersect with mesh

Description

Cast rays to intersect with mesh

Usage

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

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

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)
)