Auto-frame a camera to fit a mesh or vertex set

Computes a camera position that frames the entire mesh in view. The camera looks along the given direction, positioned at a distance that ensures the mesh fits within the field of view.

Usage

camera_auto(
  mesh,
  direction = c(0, 0, -1),
  up = c(0, 1, 0),
  fov = 45,
  margin = 1.1,
  rgl_compat = FALSE,
  projection = c("perspective", "orthographic")
)

Arguments

mesh: Either an Nx3 numeric matrix of vertex positions, or a mesh descriptor list with a vertices component.
direction: The view direction as a length-3 vector. For example, c(0, 0, -1) looks along the negative Z axis. Ignored when rgl_compat = TRUE.
up: The up vector as a length-3 vector. Default c(0, 1, 0). Ignored when rgl_compat = TRUE.
fov: Field of view in degrees. Default 45° (30° when rgl_compat = TRUE).
margin: Extra margin factor (1.0 = tight fit, 1.1 = 10% margin).
rgl_compat: Logical. If TRUE, use rgl's camera defaults and bounding-sphere distance formula. Default FALSE.
projection: Projection type: "perspective" (default) or "orthographic". When orthographic, the camera distance is computed to tightly frame the mesh regardless of FOV.

Value

A camera list, with S3 class "scimesh_camera".

Details

When rgl_compat = TRUE, the camera mimics rgl's default auto-framing behaviour: a 30° FOV, 15° elevation, and the distance is computed from the bounding sphere of the mesh (the half-diagonal of the axis-aligned bounding box), reproducing the formula distance = sphere_radius / sin(FOV/2) used by rgl.

Examples

verts <- matrix(c(-1,-1,-1, 1,-1,-1, 1,1,-1, -1,1,-1,
                   -1,-1, 1, 1,-1, 1, 1,1, 1, -1,1, 1), ncol = 3, byrow = TRUE)
tris <- matrix(c(0L,3L,2L, 0L,2L,1L, 4L,5L,6L, 4L,6L,7L,
                  0L,1L,5L, 0L,5L,4L, 2L,3L,7L, 2L,7L,6L,
                  0L,4L,7L, 0L,7L,3L, 1L,2L,6L, 1L,6L,5L), ncol = 3, byrow = TRUE)
mesh <- list(vertices = verts, triangles = tris)
cam <- camera_auto(mesh, direction = c(1, 1, 1))
cam_rgl <- camera_auto(mesh, rgl_compat = TRUE)