Calculate Animation Coordinates from Path — convert_path_to_animation

Transforms latitude/longitude/altitude coordinates to the reference system used in `render_highquality()`, so they can be used to create high quality pathtraced animations by passing the output to the `animation_camera_coords` argument in `render_highquality()`.

This function converts the path values to rayshader coordinates (by setting `return_coords = TRUE` in `render_path()`) and then subtracts out the rgl y-offset, which can be obtained by calling the internal function `rayshader:::get_scene_depth()`.

convert_path_to_animation_coords(
  lat,
  long = NULL,
  altitude = NULL,
  extent = NULL,
  frames = 360,
  reorder = FALSE,
  reorder_first_index = 1,
  reorder_duplicate_tolerance = 0.1,
  reorder_merge_tolerance = 1,
  simplify_tolerance = 0,
  zscale = 1,
  heightmap = NULL,
  offset = 5,
  type = "bezier",
  offset_lookat = 1,
  constant_step = TRUE,
  curvature_adjust = "none",
  curvature_scale = 30,
  follow_camera = FALSE,
  follow_distance = 100,
  follow_angle = 45,
  follow_rotations = 0,
  follow_fixed = FALSE,
  follow_fixed_offset = c(10, 10, 10),
  damp_motion = FALSE,
  damp_magnitude = 0.1,
  resample_path_evenly = TRUE,
  ...
)

Arguments

lat: Vector of latitudes (or other coordinate in the same coordinate reference system as extent).
long: Vector of longitudes (or other coordinate in the same coordinate reference system as extent).
altitude: Elevation of each point, in units of the elevation matrix (scaled by zscale). If left `NULL`, this will be just the elevation value at ths surface, offset by `offset`. If a single value, all data will be rendered at that altitude.
extent: Either an object representing the spatial extent of the scene (either from the `raster`, `terra`, `sf`, or `sp` packages), a length-4 numeric vector specifying `c("xmin", "xmax","ymin","ymax")`, or the spatial object (from the previously aforementioned packages) which will be automatically converted to an extent object.
frames: Default `360`. Total number of animation frames.
reorder: Default `TRUE`. If `TRUE`, this will attempt to re-order the rows within an `sf` object with multiple paths to be one continuous, end-to-end path. This happens in two steps: merging duplicate paths that have end points that match with another object (within `reorder_duplicate_tolerance` distance), and then merges them (within `reorder_merge_tolerance` distance) to form a continuous path.
reorder_first_index: Default `1`. The index (row) of the `sf` object in which to begin the reordering process. This merges and reorders paths within `reorder_merge_tolerance` distance until it cannot merge any more, and then repeats the process in the opposite direction.
reorder_duplicate_tolerance: Default `0.1`. Lines that have start and end points (does not matter which) within this tolerance that match a line already processed (order determined by `reorder_first_index`) will be discarded.
reorder_merge_tolerance: Default `1`. Lines that have start points that are within this distance to a previously processed line's end point (order determined by `reorder_first_index`) will be reordered within the `sf` object to form a continuous, end-to-end path.
simplify_tolerance: Default `0` (no simplification). If greater than zero, simplifies the path to the tolerance specified. This happens after the data has been merged if `reorder = TRUE`. If the input data is specified with long-lat coordinates and `sf_use_s2()` returns `TRUE`, then the value of simplify_tolerance must be specified in meters.
zscale: Default `1`. The ratio between the x and y spacing (which are assumed to be equal) and the z axis in the original heightmap.
heightmap: Default `NULL`. Automatically extracted from the rgl window–only use if auto-extraction of matrix extent isn't working. A two-dimensional matrix, where each entry in the matrix is the elevation at that point. All points are assumed to be evenly spaced.
offset: Default `5`. Offset of the track from the surface, if `altitude = NULL`.
type: Default `cubic`. Type of transition between keyframes. Other options are `linear`, `quad`, `bezier`, `exp`, and `manual`. `manual` just returns the values passed in, properly formatted to be passed to `render_animation()`.
offset_lookat: Default `0`. Amount to offset the lookat position, either along the path (if `constant_step = TRUE`) or towards the derivative of the Bezier curve.
constant_step: Default `TRUE`. This will make the camera travel at a constant speed.
curvature_adjust: Default `none`. Other options are `position`, `lookat`, and `both`. Whether to slow down the camera at areas of high curvature to prevent fast swings. Only used for curve `type = bezier`. This does not preserve key frame positions. Note: This feature will likely result in the `lookat` and `position` diverging if they do not have similar curvatures at each point. This feature is best used when passing the same set of points to `positions` and `lookats` and providing an `offset_lookat` value, which ensures the curvature will be the same.
curvature_scale: Default `30`. Constant dividing factor for curvature. Higher values will subdivide the path more, potentially finding a smoother path, but increasing the calculation time. Only used for curve `type = bezier`. Increasing this value after a certain point will not increase the quality of the path, but it is scene-dependent.
follow_camera: Default `FALSE`. If `TRUE`, this generates a 3rd person view that follows the path specified in `lat`, `long`, and `altitude`. The distance to the camera is specified by `follow_distance`, and the angle (off the ground) is specified by `follow_angle`. Make the camera rotate around the point as it moves by setting `follow_rotations` to a non-zero number. The camera points in the direction of the You can also set the camera to be a fixed distance and angle above the by settings `follow_fixed = TRUE` and specifying the distance in `follow_fixed_offset`.
follow_distance: Default `100`. Distance for the camera to follow the point when `follow_camera = TRUE`.
follow_angle: Default `45`. Angle (off the ground) of the camera when `follow_camera = TRUE`.
follow_rotations: Default `0`. Number of rotations around the point when `follow_camera = TRUE`.
follow_fixed: Default `FALSE`. If `TRUE`, the camera doesn't look in the direction of the path, but rather sits at a fixed relative location to the path.
follow_fixed_offset: Default `c(10,10,10)`. If `follow_fixed = TRUE`, the offset from the path to place the camera.
damp_motion: Default `FALSE`. Whether the suppress quick, jerky movements of the camera by linearly interpolating between the current camera position and the goal position. Amount of linear interpolation set in `damp_magnitude`.
damp_magnitude: Default `0.1`. Amount of linear interpolation if `damp_motion = TRUE`.
resample_path_evenly: Default `TRUE`. This re-samples points along the path so that the camera moves at a constant speed along the path. This also allows paths with large numbers of points to be used with a smaller number of frames, and improves computation time of the animation path in those instances.
...: Other arguments to pass to `rayrender::generate_camera_motion()`

Examples

#Generate a circle in Monterey Bay and fly around on top of it
if(run_documentation()) {
montereybay %>%
 sphere_shade() %>%
 plot_3d(montereybay,zscale=50,water=TRUE,
         shadowcolor="#40310a", background = "tan",
         theta=210,  phi=22, zoom=0.40, fov=55)
         
moss_landing_coord = c(36.806807, -121.793332)
t = seq(0,2*pi,length.out=1000)
circle_coords_lat = moss_landing_coord[1] + 0.25 * sin(t)
circle_coords_long = moss_landing_coord[2] + 0.25  *  cos(t)
render_path(extent = attr(montereybay,"extent"), heightmap = montereybay,
           lat = unlist(circle_coords_lat), long = unlist(circle_coords_long),
           zscale=50, color="red", antialias=TRUE,
           offset=100, linewidth=2)
render_snapshot()

camera_path = convert_path_to_animation_coords(extent = attr(montereybay,"extent"), 
                                              heightmap = montereybay,
                                              lat = unlist(circle_coords_lat), 
                                              long = unlist(circle_coords_long),
                                              fovs = 80,
                                              zscale=50, offset=250, frames = 25)

#Render a series of frames, following the path specified above
temp_dir = tempdir()
render_highquality(samples=16, animation_camera_coords = camera_path, 
                  width=200,height=200, filename = sprintf("%s/frame",temp_dir),
                  use_extruded_paths = TRUE,
                  sample_method="sobol_blue")

#Plot all these frames
image_list = list()
for(i in 1:25) {
  image_list[[i]] = png::readPNG(sprintf("%s/frame%d.png",temp_dir,i))
}
rayimage::plot_image_grid(image_list, dim = c(5,5))
}
#> Error: Expecting a single string value: [type=list; extent=1].


if(run_documentation()) {
#Now render a third-person view by setting `follow_camera = TRUE`
camera_path = convert_path_to_animation_coords(extent = attr(montereybay,"extent"), 
                                              heightmap = montereybay,
                                              lat = unlist(circle_coords_lat), 
                                              long = unlist(circle_coords_long),
                                              fovs = 80,
                                              follow_camera = TRUE,
                                              zscale=50, offset=250, frames = 25)

#Render a series of frames, following the path specified above
temp_dir = tempdir()
render_highquality(samples=16, animation_camera_coords = camera_path, 
                  width=200,height=200, filename = sprintf("%s/frame",temp_dir),
                  use_extruded_paths = TRUE,
                  sample_method="sobol_blue")

#Plot all these frames
image_list = list()
for(i in 1:25) {
  image_list[[i]] = png::readPNG(sprintf("%s/frame%d.png",temp_dir,i))
}
rayimage::plot_image_grid(image_list, dim = c(5,5))
}
#> Error: Expecting a single string value: [type=list; extent=1].