computeContour3d {misc3d}

Compute Isosurface, a Three Dimension Contour

Description

Computes a 3D contours or isosurface by the marching cubes algorithm.

Usage

computeContour3d(vol, maxvol = max(vol), level,
                 x = 1:dim(vol)[1],
                 y = 1:dim(vol)[2],
                 z = 1:dim(vol)[3], mask)

Arguments

vol

a three dimensional array.

maxvol

maximum of the vol array.

level

The level at which to construct the contour surface.

x, y, z

locations of grid planes at which values in vol are measured.

mask

a function of 3 arguments returning a logical array, a three dimensional logical array, or NULL. If not NULL, only cells for which mask is true at all eight vertices are used in forming the contour.

Details

Uses the marching-cubes algorithm, with adjustments for dealing with face and internal ambiguities, to compute an isosurface. See references for the details. The function contour3d provides a higher-level interface.

Value

A matrix of three columns representing the triangles making up the contour surface. Each row represents a vertex and goups of three rows represent a triangle.

References

Chernyaev E. (1995) Marching Cubes 33: Construction of Topologically Correct Isosurfaces Technical Report CN/95-17, CERN

Lorensen W. and Cline H. (1987) Marching Cubes: A High Resolution 3D Surface Reconstruction Algorithm Computer Graphics vol. 21, no. 4, 163-169

Nielson G. and Hamann B. (1992) The Asymptotic Decider: Resolving the Ambiguity in Marching Cubes Proc. IEEE Visualization 92, 83-91

See Also

contour3d

Examples

  x <- seq(-2,2,len=50)
  g <- expand.grid(x = x, y = x, z = x)
  v <- array(g$x^4 + g$y^4 + g$z^4, rep(length(x),3))
  con <- computeContour3d(v, max(v), 1)
  drawScene(makeTriangles(con))