isosurface (MATLAB Functions)

Extract isosurface data from volume data

Syntax

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

Description

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 define the coordinates for the volume V. The structure 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(...) returns the faces and vertices in two arrays instead of a struct.

isosurface(...) with no output arguments creates a patch using the computed faces and vertices.

Special Case Behavior -- isosurface Called with No Output Arguments

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.

Remarks

You can pass the fv structure created by isosurface directly to the patch command, but you cannot pass the individual faces and vertices arrays (f, v) to patch without specifying property names. For example,

```
patch(isosurface(X,Y,Z,V,isovalue))
```

[f,v] = isosurface(X,Y,Z,V,isovalue);
patch('Faces',f,'Vertices',v)

Examples

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)
Setting the face and edge color (set, FaceColor, EdgeColor)
Specifying the view (daspect, view)
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

Connecting Equal Values with Isosurfaces for more examples

Volume Visualization for related functions

isonormals ispc