Figure 15.5: Mesh plot.
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The function mesh produces mesh surface plots. For example,
tx = ty = linspace (-8, 8, 41)';
[xx, yy] = meshgrid (tx, ty);
r = sqrt (xx .^ 2 + yy .^ 2) + eps;
tz = sin (r) ./ r;
mesh (tx, ty, tz);
xlabel ("tx");
ylabel ("ty");
zlabel ("tz");
title ("3-D Sombrero plot");
produces the familiar “sombrero” plot shown in Figure 15.5. Note
the use of the function meshgrid to create matrices of X and Y
coordinates to use for plotting the Z data. The ndgrid function
is similar to meshgrid, but works for N-dimensional matrices.
The meshc function is similar to mesh, but also produces a
plot of contours for the surface.
The plot3 function displays arbitrary three-dimensional data,
without requiring it to form a surface. For example,
t = 0:0.1:10*pi;
r = linspace (0, 1, numel (t));
z = linspace (0, 1, numel (t));
plot3 (r.*sin (t), r.*cos (t), z);
xlabel ("r.*sin (t)");
ylabel ("r.*cos (t)");
zlabel ("z");
title ("plot3 display of 3-D helix");
displays the spiral in three dimensions shown in Figure 15.6.
Finally, the view function changes the viewpoint for
three-dimensional plots.
Plot a 3-D wireframe mesh.
The wireframe mesh is plotted using rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the mesh is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally, the color of the mesh can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
See also: ezmesh, meshc, meshz, trimesh, contour, surf, surface, meshgrid, hidden, shading, colormap, caxis.
Plot a 3-D wireframe mesh with underlying contour lines.
The wireframe mesh is plotted using rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the mesh is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally the color of the mesh can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a 2-element vector with a graphics handle to the created surface object and to the created contour plot.
See also: ezmeshc, mesh, meshz, contour, surfc, surface, meshgrid, hidden, shading, colormap, caxis.
Plot a 3-D wireframe mesh with a surrounding curtain.
The wireframe mesh is plotted using rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 0:(columns (z) - 1), y = 0:(rows (z) - 1).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the mesh is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally the color of the mesh can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
See also: mesh, meshc, contour, surf, surface, waterfall, meshgrid, hidden, shading, colormap, caxis.
Control mesh hidden line removal.
When called with no argument the hidden line removal state is toggled.
When called with one of the modes "on" or "off" the state
is set accordingly.
The optional output argument mode is the current state.
Hidden Line Removal determines what graphic objects behind a mesh plot are visible. The default is for the mesh to be opaque and lines behind the mesh are not visible. If hidden line removal is turned off then objects behind the mesh can be seen through the faces (openings) of the mesh, although the mesh grid lines are still opaque.
See also: mesh, meshc, meshz, ezmesh, ezmeshc, trimesh, waterfall.
Plot a 3-D surface mesh.
The surface mesh is plotted using shaded rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the surface is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally, the color of the surface can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
Note: The exact appearance of the surface can be controlled with the
shading command or by using set to control surface object
properties.
See also: ezsurf, surfc, surfl, surfnorm, trisurf, contour, mesh, surface, meshgrid, hidden, shading, colormap, caxis.
Plot a 3-D surface mesh with underlying contour lines.
The surface mesh is plotted using shaded rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the surface is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally, the color of the surface can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
Note: The exact appearance of the surface can be controlled with the
shading command or by using set to control surface object
properties.
See also: ezsurfc, surf, surfl, surfnorm, trisurf, contour, mesh, surface, meshgrid, hidden, shading, colormap, caxis.
Plot a 3-D surface using shading based on various lighting models.
The surface mesh is plotted using shaded rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The default lighting mode "cdata", changes the cdata property of the
surface object to give the impression of a lighted surface.
Warning: The alternative mode "light" mode which creates a
light object to illuminate the surface is not implemented (yet).
The light source location can be specified using lsrc. It can be given as a 2-element vector [azimuth, elevation] in degrees, or as a 3-element vector [lx, ly, lz]. The default value is rotated 45 degrees counterclockwise to the current view.
The material properties of the surface can specified using a 4-element vector P = [AM D SP exp] which defaults to p = [0.55 0.6 0.4 10].
"AM" strength of ambient light"D" strength of diffuse reflection"SP" strength of specular reflection"EXP" specular exponentIf the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
Example:
colormap (bone (64)); surfl (peaks); shading interp;
See also: diffuse, specular, surf, shading, colormap, caxis.
Find the vectors normal to a meshgridded surface.
If x and y are vectors, then a typical vertex is
(x(j), y(i), z(i,j)). Thus, columns of z correspond
to different x values and rows of z correspond to different
y values. If only a single input z is given then x is
taken to be 1:columns (z) and y is
1:rows (z).
If no return arguments are requested, a surface plot with the normal vectors to the surface is plotted.
Any property/value input pairs are assigned to the surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
If output arguments are requested then the components of the normal vectors are returned in nx, ny, and nz and no plot is made. The normal vectors are unnormalized (magnitude != 1). To normalize, use
len = sqrt (nx.^2 + ny.^2 + nz.^2); nx ./= len; ny ./= len; nz ./= len;
An example of the use of surfnorm is
surfnorm (peaks (25));
Algorithm: The normal vectors are calculated by taking the cross product of the diagonals of each of the quadrilateral faces in the meshgrid to find the normal vectors at the center of each face. Next, for each meshgrid point the four nearest normal vectors are averaged to obtain the final normal to the surface at the meshgrid point.
For surface objects, the "VertexNormals" property contains
equivalent information, except possibly near the boundary of the surface
where different interpolation schemes may yield slightly different values.
See also: isonormals, quiver3, surf, meshgrid.
Calculate isosurface of 3-D volume data.
An isosurface connects points with the same value and is analogous to a contour plot, but in three dimensions.
The input argument v is a three-dimensional array that contains data sampled over a volume.
The input isoval is a scalar that specifies the value for the isosurface. If isoval is omitted or empty, a "good" value for an isosurface is determined from v.
When called with a single output argument isosurface returns a
structure array fv that contains the fields faces and
vertices computed at the points
[x, y, z] = meshgrid (1:l, 1:m, 1:n) where
[l, m, n] = size (v). The output fv can be
used directly as input to the patch function.
If called with additional input arguments x, y, and z
that are three-dimensional arrays with the same size as v or
vectors with lengths corresponding to the dimensions of v, then the
volume data is taken at the specified points. If x, y, or
z are empty, the grid corresponds to the indices (1:n) in
the respective direction (see meshgrid).
The optional input argument col, which is a three-dimensional array of the same size as v, specifies coloring of the isosurface. The color data is interpolated, as necessary, to match isoval. The output structure array, in this case, has the additional field facevertexcdata.
If given the string input argument "noshare", vertices may be
returned multiple times for different faces. The default behavior is to
eliminate vertices shared by adjacent faces with unique which may be
time consuming.
The string input argument "verbose" is supported for MATLAB
compatibility, but has no effect.
Any string arguments must be passed after the other arguments.
If called with two or three output arguments, return the information about the faces f, vertices v, and color data c as separate arrays instead of a single structure array.
If called with no output argument, the isosurface geometry is directly
plotted with the patch command and a light object is added to
the axes if not yet present.
For example,
[x, y, z] = meshgrid (1:5, 1:5, 1:5); v = rand (5, 5, 5); isosurface (x, y, z, v, .5);
will directly draw a random isosurface geometry in a graphics window.
An example of an isosurface geometry with different additional coloring:
N = 15; # Increase number of vertices in each direction
iso = .4; # Change isovalue to .1 to display a sphere
lin = linspace (0, 2, N);
[x, y, z] = meshgrid (lin, lin, lin);
v = abs ((x-.5).^2 + (y-.5).^2 + (z-.5).^2);
figure ();
subplot (2,2,1); view (-38, 20);
[f, vert] = isosurface (x, y, z, v, iso);
p = patch ("Faces", f, "Vertices", vert, "EdgeColor", "none");
pbaspect ([1 1 1]);
isonormals (x, y, z, v, p)
set (p, "FaceColor", "green", "FaceLighting", "gouraud");
light ("Position", [1 1 5]);
subplot (2,2,2); view (-38, 20);
p = patch ("Faces", f, "Vertices", vert, "EdgeColor", "blue");
pbaspect ([1 1 1]);
isonormals (x, y, z, v, p)
set (p, "FaceColor", "none", "EdgeLighting", "gouraud");
light ("Position", [1 1 5]);
subplot (2,2,3); view (-38, 20);
[f, vert, c] = isosurface (x, y, z, v, iso, y);
p = patch ("Faces", f, "Vertices", vert, "FaceVertexCData", c, ...
"FaceColor", "interp", "EdgeColor", "none");
pbaspect ([1 1 1]);
isonormals (x, y, z, v, p)
set (p, "FaceLighting", "gouraud");
light ("Position", [1 1 5]);
subplot (2,2,4); view (-38, 20);
p = patch ("Faces", f, "Vertices", vert, "FaceVertexCData", c, ...
"FaceColor", "interp", "EdgeColor", "blue");
pbaspect ([1 1 1]);
isonormals (x, y, z, v, p)
set (p, "FaceLighting", "gouraud");
light ("Position", [1 1 5]);
See also: isonormals, isocolors, isocaps, smooth3, reducevolume, reducepatch, patch.
Calculate normals to an isosurface.
The vertex normals vn are calculated from the gradient of the 3-dimensional array val (size: lxmxn) with the data for an isosurface geometry. The normals point towards lower values in val.
If called with one output argument vn and the second input argument
vert holds the vertices of an isosurface, the normals vn are
calculated at the vertices vert on a grid given by
[x, y, z] = meshgrid (1:l, 1:m, 1:n). The output argument
vn has the same size as vert and can be used to set the
"VertexNormals" property of the corresponding patch.
If called with further input arguments x, y, and z which are 3-dimensional arrays with the same size as val, the volume data is taken at these points. Instead of the vertex data vert, a patch handle hp can be passed to this function.
If the last input argument is the string "negate", compute the
reverse vector normals of an isosurface geometry (i.e., pointed towards
higher values in val).
If no output argument is given, the property "VertexNormals" of
the patch associated with the patch handle hp is changed directly.
See also: isosurface, isocolors, smooth3.
"verbose")Create end-caps for isosurfaces of 3-D data.
This function places caps at the open ends of isosurfaces.
The input argument v is a three-dimensional array that contains data sampled over a volume.
The input isoval is a scalar that specifies the value for the isosurface. If isoval is omitted or empty, a "good" value for an isosurface is determined from v.
When called with a single output argument, isocaps returns a
structure array fvc with the fields: faces, vertices,
and facevertexcdata. The results are computed at the points
[x, y, z] = meshgrid (1:l, 1:m, 1:n) where
[l, m, n] = size (v). The output fvc can be used
directly as input to the patch function.
If called with additional input arguments x, y, and z
that are three-dimensional arrays with the same size as v or
vectors with lengths corresponding to the dimensions of v, then the
volume data is taken at the specified points. If x, y, or
z are empty, the grid corresponds to the indices (1:n) in
the respective direction (see meshgrid).
The optional parameter which_caps can have one of the following string values which defines how the data will be enclosed:
"above", "a" (default)for end-caps that enclose the data above isoval.
"below", "b"for end-caps that enclose the data below isoval.
The optional parameter which_plane can have one of the following string values to define which end-cap should be drawn:
"all" (default)for all of the end-caps.
"xmin"for end-caps at the lower x-plane of the data.
"xmax"for end-caps at the upper x-plane of the data.
"ymin"for end-caps at the lower y-plane of the data.
"ymax"for end-caps at the upper y-plane of the data.
"zmin"for end-caps at the lower z-plane of the data.
"zmax"for end-caps at the upper z-plane of the data.
The string input argument "verbose" is supported for MATLAB
compatibility, but has no effect.
If called with two or three output arguments, the data for faces faces, vertices vertices, and the color data facevertexcdata are returned in separate arrays instead of a single structure.
If called with no output argument, the end-caps are drawn directly in the
current figure with the patch command.
See also: isosurface, isonormals, patch.
Compute isosurface colors.
If called with one output argument and the first input argument
c is a three-dimensional array that contains color values and
the second input argument v keeps the vertices of a geometry
then return a matrix cd with color data information for the
geometry at computed points
[x, y, z] = meshgrid (1:l, 1:m, 1:n). The output argument
cd can be taken to manually set FaceVertexCData of a patch.
If called with further input arguments x, y and z
which are three–dimensional arrays of the same size than c
then the color data is taken at those given points. Instead of the
color data c this function can also be called with RGB values
r, g, b. If input argumnets x, y,
z are not given then again meshgrid computed values
are taken.
Optionally, the patch handle p can be given as the last input argument to all variations of function calls instead of the vertices data v. Finally, if no output argument is given then directly change the colors of a patch that is given by the patch handle p.
For example:
function isofinish (p)
set (gca, "PlotBoxAspectRatioMode", "manual", ...
"PlotBoxAspectRatio", [1 1 1]);
set (p, "FaceColor", "interp");
## set (p, "FaceLighting", "flat");
## light ("Position", [1 1 5]); # Available with JHandles
endfunction
N = 15; # Increase number of vertices in each direction
iso = .4; # Change isovalue to .1 to display a sphere
lin = linspace (0, 2, N);
[x, y, z] = meshgrid (lin, lin, lin);
c = abs ((x-.5).^2 + (y-.5).^2 + (z-.5).^2);
figure (); # Open another figure window
subplot (2,2,1); view (-38, 20);
[f, v] = isosurface (x, y, z, c, iso);
p = patch ("Faces", f, "Vertices", v, "EdgeColor", "none");
cdat = rand (size (c)); # Compute random patch color data
isocolors (x, y, z, cdat, p); # Directly set colors of patch
isofinish (p); # Call user function isofinish
subplot (2,2,2); view (-38, 20);
p = patch ("Faces", f, "Vertices", v, "EdgeColor", "none");
[r, g, b] = meshgrid (lin, 2-lin, 2-lin);
cdat = isocolors (x, y, z, c, v); # Compute color data vertices
set (p, "FaceVertexCData", cdat); # Set color data manually
isofinish (p);
subplot (2,2,3); view (-38, 20);
p = patch ("Faces", f, "Vertices", v, "EdgeColor", "none");
cdat = isocolors (r, g, b, c, p); # Compute color data patch
set (p, "FaceVertexCData", cdat); # Set color data manually
isofinish (p);
subplot (2,2,4); view (-38, 20);
p = patch ("Faces", f, "Vertices", v, "EdgeColor", "none");
r = g = b = repmat ([1:N] / N, [N, 1, N]); # Black to white
cdat = isocolors (x, y, z, r, g, b, v);
set (p, "FaceVertexCData", cdat);
isofinish (p);
See also: isosurface, isonormals.
Smooth values of 3-dimensional matrix data.
This function can be used, for example, to reduce the impact of noise in data before calculating isosurfaces.
data must be a non-singleton 3-dimensional matrix. The smoothed data from this matrix is returned in smoothed_data which is of the same size as data.
The option input method determines which convolution kernel is used for the smoothing process. Possible choices:
"box", "b" (default)to use a convolution kernel with sharp edges.
"gaussian", "g"to use a convolution kernel that is represented by a non-correlated trivariate normal distribution function.
sz is either a vector of 3 elements representing the size of the convolution kernel in x-, y- and z-direction or a scalar, in which case the same size is used in all three dimensions. The default value is 3.
When method is "gaussian", std_dev defines the standard
deviation of the trivariate normal distribution function. std_dev is
either a vector of 3 elements representing the standard deviation of the
Gaussian convolution kernel in x-, y- and z-directions or a scalar, in which
case the same value is used in all three dimensions. The default value is
0.65.
See also: isosurface, isonormals, patch.
Reduce the volume of the dataset in v according to the values in r.
v is a matrix that is non-singleton in the first 3 dimensions.
r can either be a vector of 3 elements representing the reduction factors in the x-, y-, and z-directions or a scalar, in which case the same reduction factor is used in all three dimensions.
reducevolume reduces the number of elements of v by taking
only every r-th element in the respective dimension.
Optionally, x, y, and z can be supplied to represent the set of coordinates of v. They can either be matrices of the same size as v or vectors with sizes according to the dimensions of v, in which case they are expanded to matrices (see meshgrid).
If reducevolume is called with two arguments then x, y,
and z are assumed to match the respective indices of v.
The reduced matrix is returned in nv.
Optionally, the reduced set of coordinates are returned in nx, ny, and nz, respectively.
Examples:
v = reshape (1:6*8*4, [6 8 4]); nv = reducevolume (v, [4 3 2]);
v = reshape (1:6*8*4, [6 8 4]); x = 1:3:24; y = -14:5:11; z = linspace (16, 18, 4); [nx, ny, nz, nv] = reducevolume (x, y, z, v, [4 3 2]);
See also: isosurface, isonormals.
Reduce the number of faces and vertices in a patch object while retaining the overall shape of the patch.
The input patch can be represented by a structure fv with the
fields faces and vertices, by two matrices faces and
vertices (see, e.g., the result of isosurface), or by a
handle to a patch object patch_handle (see patch).
The number of faces and vertices in the patch is reduced by iteratively collapsing the shortest edge of the patch to its midpoint (as discussed, e.g., here: http://libigl.github.io/libigl/tutorial/tutorial.html#meshdecimation).
Currently, only patches consisting of triangles are supported. The resulting patch also consists only of triangles.
If reducepatch is called with a handle to a valid patch
patch_handle, and without any output arguments, then the given
patch is updated immediately.
If the reduction_factor is omitted, the resulting structure reduced_fv includes approximately 50% of the faces of the original patch. If reduction_factor is a fraction between 0 (excluded) and 1 (excluded), a patch with approximately the corresponding fraction of faces is determined. If reduction_factor is an integer greater than or equal to 1, the resulting patch has approximately reduction_factor faces. Depending on the geometry of the patch, the resulting number of faces can differ from the given value of reduction_factor. This is especially true when many shared vertices are detected.
For the reduction, it is necessary that vertices of touching faces are
shared. Shared vertices are detected automatically. This detection can be
skipped by passing the optional string argument "fast".
With the optional string arguments "verbose", additional status
messages are printed to the command window.
Any string input arguments must be passed after all other arguments.
If called with one output argument, the reduced faces and vertices are
returned in a structure reduced_fv with the fields faces and
vertices (see the one output option of isosurface).
If called with two output arguments, the reduced faces and vertices are returned in two separate matrices reduced_faces and reduced_vertices.
See also: isosurface, isonormals, reducevolume, patch.
Reduce the size of faces in a patch by the shrink factor sf.
The patch object can be specified by a graphics handle (p), a patch
structure (fv) with the fields "faces" and "vertices",
or as two separate matrices (f, v) of faces and vertices.
The shrink factor sf is a positive number specifying the percentage of the original area the new face will occupy. If no factor is given the default is 0.3 (a reduction to 30% of the original size). A factor greater than 1.0 will result in the expansion of faces.
Given a patch handle as the first input argument and no output parameters, perform the shrinking of the patch faces in place and redraw the patch.
If called with one output argument, return a structure with fields
"faces", "vertices", and "facevertexcdata"
containing the data after shrinking. This structure can be used directly
as an input argument to the patch function.
Caution:: Performing the shrink operation on faces which are not convex can lead to undesirable results.
Example: a triangulated 3/4 circle and the corresponding shrunken version.
[phi r] = meshgrid (linspace (0, 1.5*pi, 16), linspace (1, 2, 4));
tri = delaunay (phi(:), r(:));
v = [r(:).*sin(phi(:)) r(:).*cos(phi(:))];
clf ()
p = patch ("Faces", tri, "Vertices", v, "FaceColor", "none");
fv = shrinkfaces (p);
patch (fv)
axis equal
grid on
See also: patch.
Calculate the diffuse reflection strength of a surface defined by the normal vector elements sx, sy, sz.
The light source location vector lv can be given as a 2-element vector [azimuth, elevation] in degrees or as a 3-element vector [x, y, z].
Calculate the specular reflection strength of a surface defined by the normal vector elements sx, sy, sz using Phong’s approximation.
The light source location and viewer location vectors are specified using parameters lv and vv respectively. The location vectors can given as 2-element vectors [azimuth, elevation] in degrees or as 3-element vectors [x, y, z].
An optional sixth argument specifies the specular exponent (spread) se. If not given, se defaults to 10.
Set the lighting of patch or surface graphic objects.
Valid arguments for type are
"flat"Draw objects with faceted lighting effects.
"gouraud"Draw objects with linear interpolation of the lighting effects between the vertices.
"none"Draw objects without light and shadow effects.
If the first argument hax is an axes handle, then change the lighting
effects of objects in this axes, rather than the current axes returned by
gca.
The lighting effects are only visible if at least one light object is present and visible in the same axes.
See also: light, fill, mesh, patch, pcolor, surf, surface, shading.
Set reflectance properties for the lighting of surfaces and patches.
This function changes the ambient, diffuse, and specular strengths, as well
as the specular exponent and specular color reflectance, of all
patch and surface objects in the current axes. This can be
used to simulate, to some extent, the reflectance properties of certain
materials when used with light.
When called with a string, the aforementioned properties are set according to the values in the following table:
| mtype | ambient- strength | diffuse- strength | specular- strength | specular- exponent | specular- color- reflectance | ||
|---|---|---|---|---|---|---|---|
"shiny" | 0.3 | 0.6 | 0.9 | 20 | 1.0 | ||
"dull" | 0.3 | 0.8 | 0.0 | 10 | 1.0 | ||
"metal" | 0.3 | 0.3 | 1.0 | 25 | 0.5 | ||
"default" | "default" | "default" | "default" | "default" | "default" |
When called with a vector of three elements, the ambient, diffuse, and
specular strengths of all patch and surface objects in the
current axes are updated. An optional fourth vector element updates the
specular exponent, and an optional fifth vector element updates the
specular color reflectance.
A list of graphic handles can also be passed as the first argument. In
this case, the properties of these handles and all child patch and
surface objects will be updated.
Additionally, material can be called with a single output argument.
If called without input arguments, a column cell vector mtypes with
the strings for all available materials is returned. If the one input
argument mtype_string is the name of a material, a 1x5 cell vector
refl_props with the reflectance properties of that material is
returned. In both cases, no graphic properties are changed.
Add a light object to a figure using a simple interface.
When called with no arguments, a light object is added to the current plot
and is placed slightly above and to the right of the camera’s current
position: this is equivalent to camlight right. The commands
camlight left and camlight headlight behave similarly with
the placement being either left of the camera position or centered on the
camera position.
For more control, the light position can be specified by an azimuthal rotation az and an elevation angle el, both in degrees, relative to the current properties of the camera.
The optional string style specifies whether the light is a local point
source ("local", the default) or placed at infinite distance
("infinite").
If the first argument hl is a handle to a light object, then act on this light object rather than creating a new object.
The optional return value h is a graphics handle to the light object. This can be used to move or further change properties of the light object.
Examples:
Add a light object to a plot
sphere (36); camlight
Position the light source exactly
camlight (45, 30);
Here the light is first pitched upwards from the camera position by 30 degrees. It is then yawed by 45 degrees to the right. Both rotations are centered around the camera target.
Return a handle to further manipulate the light object
clf
sphere (36);
hl = camlight ("left");
set (hl, "color", "r");
See also: light.
Given vectors of x and y coordinates, return matrices xx and yy corresponding to a full 2-D grid.
The rows of xx are copies of x, and the columns of yy are copies of y. If y is omitted, then it is assumed to be the same as x.
If the optional z input is given, or zz is requested, then the output will be a full 3-D grid.
meshgrid is most frequently used to produce input for a 2-D or 3-D
function that will be plotted. The following example creates a surface
plot of the “sombrero” function.
f = @(x,y) sin (sqrt (x.^2 + y.^2)) ./ sqrt (x.^2 + y.^2); range = linspace (-8, 8, 41); [X, Y] = meshgrid (range, range); Z = f (X, Y); surf (X, Y, Z);
Programming Note: meshgrid is restricted to 2-D or 3-D grid
generation. The ndgrid function will generate 1-D through N-D
grids. However, the functions are not completely equivalent. If x
is a vector of length M and y is a vector of length N, then
meshgrid will produce an output grid which is NxM. ndgrid
will produce an output which is MxN (transpose) for the same
input. Some core functions expect meshgrid input and others expect
ndgrid input. Check the documentation for the function in question
to determine the proper input format.
Given n vectors x1, …, xn, ndgrid returns n
arrays of dimension n.
The elements of the i-th output argument contains the elements of the vector xi repeated over all dimensions different from the i-th dimension. Calling ndgrid with only one input argument x is equivalent to calling ndgrid with all n input arguments equal to x:
[y1, y2, …, yn] = ndgrid (x, …, x)
Programming Note: ndgrid is very similar to the function
meshgrid except that the first two dimensions are transposed in
comparison to meshgrid. Some core functions expect meshgrid
input and others expect ndgrid input. Check the documentation for
the function in question to determine the proper input format.
See also: meshgrid.
Produce 3-D plots.
Many different combinations of arguments are possible. The simplest form is
plot3 (x, y, z)
in which the arguments are taken to be the vertices of the points to be plotted in three dimensions. If all arguments are vectors of the same length, then a single continuous line is drawn. If all arguments are matrices, then each column of is treated as a separate line. No attempt is made to transpose the arguments to make the number of rows match.
If only two arguments are given, as
plot3 (x, cplx)
the real and imaginary parts of the second argument are used as the y and z coordinates, respectively.
If only one argument is given, as
plot3 (cplx)
the real and imaginary parts of the argument are used as the y and z values, and they are plotted versus their index.
Arguments may also be given in groups of three as
plot3 (x1, y1, z1, x2, y2, z2, …)
in which each set of three arguments is treated as a separate line or set of lines in three dimensions.
To plot multiple one- or two-argument groups, separate each group with an empty format string, as
plot3 (x1, c1, "", c2, "", …)
Multiple property-value pairs may be specified which will affect the line
objects drawn by plot3. If the fmt argument is supplied it
will format the line objects in the same manner as plot.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created plot.
Example:
z = [0:0.05:5]; plot3 (cos (2*pi*z), sin (2*pi*z), z, ";helix;"); plot3 (z, exp (2i*pi*z), ";complex sinusoid;");
Query or set the viewpoint for the current axes.
The parameters azimuth and elevation can be given as two arguments or as 2-element vector. The viewpoint can also be specified with Cartesian coordinates x, y, and z.
The call view (2) sets the viewpoint to azimuth = 0
and elevation = 90, which is the default for 2-D graphs.
The call view (3) sets the viewpoint to azimuth = -37.5
and elevation = 30, which is the default for 3-D graphs.
If the first argument hax is an axes handle, then operate on
this axes rather than the current axes returned by gca.
If no inputs are given, return the current azimuth and elevation.
Plot slices of 3-D data/scalar fields.
Each element of the 3-dimensional array v represents a scalar value at
a location given by the parameters x, y, and z. The
parameters x, x, and z are either 3-dimensional arrays of
the same size as the array v in the "meshgrid" format or
vectors. The parameters xi, etc. respect a similar format to
x, etc., and they represent the points at which the array vi
is interpolated using interp3. The vectors sx, sy, and
sz contain points of orthogonal slices of the respective axes.
If x, y, z are omitted, they are assumed to be
x = 1:size (v, 2), y = 1:size (v, 1) and
z = 1:size (v, 3).
method is one of:
"nearest"Return the nearest neighbor.
"linear"Linear interpolation from nearest neighbors.
"cubic"Cubic interpolation from four nearest neighbors (not implemented yet).
"spline"Cubic spline interpolation—smooth first and second derivatives throughout the curve.
The default method is "linear".
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
Examples:
[x, y, z] = meshgrid (linspace (-8, 8, 32)); v = sin (sqrt (x.^2 + y.^2 + z.^2)) ./ (sqrt (x.^2 + y.^2 + z.^2)); slice (x, y, z, v, [], 0, []); [xi, yi] = meshgrid (linspace (-7, 7)); zi = xi + yi; slice (x, y, z, v, xi, yi, zi);
Draw a ribbon plot for the columns of y vs. x.
If x is omitted, a vector containing the row numbers is assumed
(1:rows (Y)). Alternatively, x can also be a vector with
same number of elements as rows of y in which case the same
x is used for each column of y.
The optional parameter width specifies the width of a single ribbon (default is 0.75).
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a vector of graphics handles to the surface objects representing each ribbon.
Set the shading of patch or surface graphic objects.
Valid arguments for type are
"flat"Single colored patches with invisible edges.
"faceted"Single colored patches with black edges.
"interp"Colors between patch vertices are interpolated and the patch edges are invisible.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
See also: fill, mesh, patch, pcolor, surf, surface, hidden, lighting.
Draw a 3-D scatter plot.
A marker is plotted at each point defined by the coordinates in the vectors x, y, and z.
The size of the markers is determined by s, which can be a scalar or a vector of the same length as x, y, and z. If s is not given, or is an empty matrix, then a default value of 8 points is used.
The color of the markers is determined by c, which can be a string defining a fixed color; a 3-element vector giving the red, green, and blue components of the color; a vector of the same length as x that gives a scaled index into the current colormap; or an Nx3 matrix defining the RGB color of each marker individually.
The marker to use can be changed with the style argument, that is a
string defining a marker in the same manner as the plot command.
If no marker is specified it defaults to "o" or circles.
If the argument "filled" is given then the markers are filled.
Additional property/value pairs are passed directly to the underlying patch object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the hggroup object representing the points.
[x, y, z] = peaks (20); scatter3 (x(:), y(:), z(:), [], z(:));
Plot a 3-D waterfall plot.
A waterfall plot is similar to a meshz plot except only
mesh lines for the rows of z (x-values) are shown.
The wireframe mesh is plotted using rectangles. The vertices of the
rectangles [x, y] are typically the output of meshgrid.
over a 2-D rectangular region in the x-y plane. z determines the
height above the plane of each vertex. If only a single z matrix is
given, then it is plotted over the meshgrid
x = 1:columns (z), y = 1:rows (z).
Thus, columns of z correspond to different x values and rows
of z correspond to different y values.
The color of the mesh is computed by linearly scaling the z values
to fit the range of the current colormap. Use caxis and/or
change the colormap to control the appearance.
Optionally the color of the mesh can be specified independently of z by supplying a color matrix, c.
Any property/value pairs are passed directly to the underlying surface object.
If the first argument hax is an axes handle, then plot into this axes,
rather than the current axes returned by gca.
The optional return value h is a graphics handle to the created surface object.
See also: meshz, mesh, meshc, contour, surf, surface, ribbon, meshgrid, hidden, shading, colormap, caxis.
| • Aspect Ratio: | ||
| • Three-dimensional Function Plotting: | ||
| • Three-dimensional Geometric Shapes: |
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