Transform a Point Cloud Using Another Stage

This stage uses another stage to modify the point cloud in the pipeline. When used with a Delaunay triangulation or a raster, it performs an operation to modify the Z coordinate of the point cloud. The interpolation method is linear in the triangle mesh and bilinear in the raster. This can typically be used to build a normalization stage.
When used with a 4x4 Rotation-Translation Matrix, it multiplies the coordinates of the points to apply the rigid transformation described by the matrix. This stage modifies the point cloud in the pipeline but does not produce any output.

Usage

transform_with(stage, operator = "-", store_in_attribute = "")

Arguments

stage: A stage that produces a triangulation, raster, or Rotation-Translation Matrix (RTM), sometimes also referred to as an "Affine Transformation Matrix". Can also be a 4x4 RTM matrix.
operator: A string. '-' and '+' are supported (only with a triangulation or a raster).
store_in_attribute: A string. Use an extra byte attribute to store the result (only with a triangulation or a raster).

Value

This stage transforms the point cloud in the pipeline. It consequently returns nothing.

RTM Matriz

Warning: lasR uses bounding boxes oriented along the XY axes of each processed chunk to manage data location and the buffer properly. Transforming the point cloud with a rotation matrix affects its bounding box and how lasR handles the buffer. When used with a matrix that has a rotational component, it is not safe to add stages after the transformation unless the user is certain that there is no buffer involved.

Examples

f <- system.file("extdata", "Topography.las", package="lasR")

# with a triangulation
mesh  <- triangulate(filter = keep_ground())
trans <- transform_with(mesh)
pipeline <- mesh + trans + write_las()
ans <- exec(pipeline, on = f)

# with a matrix
a = 20 * pi / 180
m <- matrix(c(
  cos(a), -sin(a), 0, 1000,
  sin(a), cos(a), 0, 0,
  0, 0, 1, 0,
  0, 0, 0, 1), nrow = 4, byrow = TRUE)

pipeline = transform_with(m) + write_las()
exec(pipeline, on = f)
#> $load_matrix
#>           [,1]       [,2] [,3] [,4]
#> [1,] 0.9396926 -0.3420201    0 1000
#> [2,] 0.3420201  0.9396926    0    0
#> [3,] 0.0000000  0.0000000    1    0
#> [4,] 0.0000000  0.0000000    0    1
#> 
#> $write_las
#> [1] "/tmp/RtmpUXX9w7/Topography.las"
#>