cube3D.tris {fsbrain}

Return triangles for a 3D cube or cuboid.

Description

Each row of the returned matrix encodes a point (the x, y, and z coordinates), and 3 consecutive rows encode a triangle. Obvisouly, a point will occur several times (as part of several triangles). The result can be passed to triangles3d to render a 3D box. The defaults for the parameters will create a cube with edge length 1 centered at (0, 0, 0).

Usage

cube3D.tris(
  xmin = -0.5,
  xmax = 0.5,
  ymin = -0.5,
  ymax = 0.5,
  zmin = -0.5,
  zmax = 0.5,
  center = NULL,
  edge_length = 1
)

Arguments

xmin

numeric, minimal x coordinate

xmax

numeric, maximal x coordinate

ymin

numeric, minimal y coordinate

ymax

numeric, maximal y coordinate

zmin

numeric, minimal z coordinate

zmax

numeric, maximal z coordinate

center

numeric vector of length 3 or NULL, coordinates where to center a cube with the edge length defined in parameter 'edge_length'. If this is not 'NULL', the parameters 'xmin', 'xmax', ... will be ignored, and their values will be computed for a cube based on the 'center' and 'edge_length'. Note that you can only create cubes using 'center' and 'edge_length', while the min/max methods allows the construction of cuboids.

edge_length

numeric, the edge length of the cube. Only used if parameter 'center' is used, ignored otherwise.

Value

numerical matrix with 36 rows and 3 columns, the 3D coordinates. Each row encodes a point (the x, y, and z coordinates), and 3 consecutive rows encode a triangle.

Examples

   # Create a cube with edge length 2, centered at (3,4,5):
   cube_coords = cube3D.tris(center=c(3,4,5), edge_length=2.0);
   # Create the same cube using the min/max method:
   cube_coords = cube3D.tris(xmin=2, xmax=4, ymin=3, ymax=5, zmin=4, zmax=6);
   # Create a cuboid:
   cuboid_coords = cube3D.tris(xmin=2, xmax=4, ymin=3, ymax=9, zmin=4, zmax=5);
   # To render the cuboid:
   #rgl::triangles3d(cuboid_coords, col="red");