## Documentation Center |

Extract isosurface data from volume data

`fv = isosurface(X,Y,Z,V,isovalue)fv = isosurface(V,isovalue)fvc = isosurface(...,colors)fv = isosurface(...,'noshare')fv = isosurface(...,'verbose')[f,v] = isosurface(...)[f,v,c] = isosurface(...)isosurface(...)`

`fv = isosurface(X,Y,Z,V,isovalue)` computes
isosurface data from the volume data `V` at the isosurface
value specified in `isovalue`. That is, the isosurface
connects points that have the specified value much the way contour
lines connect points of equal elevation.

The arrays `X`, `Y`, and `Z` represent
a Cartesian, axis-aligned grid. `V` contains the
corresponding values at these grid points. The coordinate arrays (`X`, `Y`,
and `Z`) must be monotonic and conform to the format
produced by `meshgrid`. `V` must
be a 3D volume array of the same size as `X`, `Y`,
and `Z`.

The `struct` `fv` contains
the faces and vertices of the isosurface, which you can pass directly
to the `patch` command.

`fv = isosurface(V,isovalue)` assumes
the arrays `X`, `Y`, and `Z` are
defined as `[X,Y,Z] = meshgrid(1:n,1:m,1:p)` where `[m,n,p]
= size(V)`.

`fvc = isosurface(...,colors)` interpolates
the array `colors` onto the scalar field and returns
the interpolated values in the `facevertexcdata` field
of the `fvc` structure. The size of the `colors` array
must be the same as `V`. The `colors` argument
enables you to control the color mapping of the isosurface with data
different from that used to calculate the isosurface (e.g., temperature
data superimposed on a wind current isosurface).

`fv = isosurface(...,'noshare')` does
not create shared vertices. This is faster, but produces a larger
set of vertices.

`fv = isosurface(...,'verbose')` prints
progress messages to the command window as the computation progresses.

`[f,v] = isosurface(...)` or
`[f,v,c] = isosurface(...)` returns
the faces and vertices (and `faceVertexcCData`) in
separate arrays instead of a struct.

`isosurface(...)` with no
output arguments, creates a patch in the current axes with the computed
faces and vertices. If no current axes exists, a new axes is created
with a 3-D view and appropriate lighting.

If there is no current axes and you call `isosurface` with
without assigning output arguments, MATLAB^{®} creates a new axes,
sets it to a 3-D view, and adds lighting to the isosurface graph.

This example uses the flow data set, which represents the speed
profile of a submerged jet within an infinite tank (type `help` `flow` for
more information). The isosurface is drawn at the data value of -3.
The statements that follow the `patch` command prepare
the isosurface for lighting by

Recalculating the isosurface normals based on the volume data (

`isonormals`)Adding lights (

`camlight`,`lighting`)[x,y,z,v] = flow; p = patch(isosurface(x,y,z,v,-3)); isonormals(x,y,z,v,p) set(p,'FaceColor','red','EdgeColor','none'); daspect([1,1,1]) view(3); axis tight camlight lighting gouraud

Visualize the same flow data as above, but color-code the surface
to indicate magnitude along the X-axis. Use a sixth argument to `isosurface`,
which provides a means to overlay another data set by coloring the
resulting isosurface. The `colors` variable is a
vector containing a scalar value for each vertex in the isosurface,
to be portrayed with the current color map. In this case, it is one
of the variables that define the surface, but it could be entirely
independent. You can apply a different color scheme by changing the
current figure color map.

[x,y,z,v] = flow; [faces,verts,colors] = isosurface(x,y,z,v,-3,x); patch('Vertices', verts, 'Faces', faces, ... 'FaceVertexCData', colors, ... 'FaceColor','interp', ... 'edgecolor', 'interp'); view(30,-15); axis vis3d; colormap copper

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