# Extracting a plane from a volume The `get.plane` function extracts a plane from a "volume" class object. ```r get.plane( vol, origin = c(0, 0, 0), plane.orientation = c(1, 0, 0, 0, 1, 0), alias = "plane.n", xgrid = NULL, ygrid = NULL, interpolate = TRUE, method = c("NN", "Av") ) ``` ## Arguments - `vol`: "volume" class object. - `origin`: Vector of x, y, z coordinates, representing the origin of the plane to extract. If `interpolate = FALSE`, these coordinates are replaced by the coordinates of the voxel closest to `origin`. - `plane.orientation`: Vector orientation of the plane in the `vol` frame of reference, composed by the 2 vectors coordinates of the orthonormal basis of the plane. First vector is x-axis, and second one is y-axis. - `alias`: `$object.alias` of the created object. - `xgrid`: Vector, representing the grid of the plane abscissa. See note. - `ygrid`: Vector, representing the grid of the plane ordinates. See note. If `ygrid = NULL`, the ordinate is the line intercepting the volume and the step is set to the projection of `vol$dxyz` onto the ordinate orientation. - `interpolate`: Boolean, default to `TRUE`. - `method`: method of interpolation, defaulted to 'NN' ie 'Nearest Neighbor'. See Details. ## Returns Returns a "volume" class object, containing only a single plane, at `k = 0`, in the same frame of reference as `vol`. This returned object has 2 new fields `local.xgrid`, and `local.ygrid`, representing the local grids of the abscissa (columns) and ordinate (rows) of the plane. Returns `NULL` if plane doesn't exist. ## Details The interpolation method is chosen from: * `'NN'`: the value of a voxel is calculated from its nearest adajcent neighbors. * `'Av'`: the value of a voxel is the weighted average of the voxels contained in a box, whose sides are automatically calculated from the `back.bol$dxyz` steps. ## Note **Determination of axes** : * the x-axis has `plane.orientation[1:3]` as unit vector. * the y-axis has `plane.orientation[4:6]` as unit vector. * If `xgrid` is not `NULL`, `origin + x.grid * plane.orientation[1:3]` are the coordinates of the points on the x axis. * If `ygrid` is not `NULL`, `origin + y.grid * plane.orientation[4:6]` are the coordinates of the points on the y axis. * If `xgrid` or `ygrid` are NULL, they are determined to represent as closely as possible the initial volume in the required cut. ## Examples ```r # loading of toy-patient objects (decrease dxyz for better result) step <- 4 patient <- toy.load.patient (modality = "mr", dxyz = rep (step, 3)) MR <- patient$mr[[1]] # mid-volume point mid.point <- apply (get.extreme.pt (MR),1,mean) plane <- get.plane (MR, origin = mid.point, interpolate = TRUE) display.kplane (plane, interpolate = FALSE) plane <- get.plane (MR, origin = mid.point, xgrid = seq (-50, 50, 1), ygrid = seq (-50, 50, 1), interpolate = TRUE) display.kplane (plane, interpolate = FALSE) # 3 points on the inclined plane pts <- t ((MR$xyz.from.ijk %*% MR$cube.idx) [1:3 , c (1, 2, 7)]) orientation <- orientation.create (A = pts[1,], B = pts[2,], C = pts[3,]) origin <- apply (pts, 2, mean) plane <- get.plane (MR, origin = origin, plane.orientation = orientation, interpolate = TRUE) display.kplane (plane, interpolate = FALSE) orientation <- orientation.create (A = c (0, 0, 0) , B = c (1, 1, 0), C = c (-1, 1, 0)) plane <- get.plane (MR, origin = origin, plane.orientation = orientation, interpolate = TRUE) display.kplane (plane, interpolate = FALSE) ```

get.plane function