MATLAB Function Reference

Surface Properties

You can set and query graphics object properties in two ways:

• The Property Editor is an interactive tool that enables you to see and change object property values.
• The set and get commands enable you to set and query the values of properties

To change the default value of properties see Setting Default Property Values.

Surface Property Descriptions

This section lists property names along with the types of values each accepts. Curly braces { } enclose default values.

The transparency data. A matrix of non-NaN values specifying the transparency of each face or vertex of the object. The AlphaData can be of class double or uint8.

MATLAB determines the transparency in one of three ways:

• Using the elements of AlphaData as transparency values (AlphaDataMapping set to none).
• Using the elements of AlphaData as indices into the current alphamap (AlphaDataMapping set to direct).
• Scaling the elements of AlphaData to range between the minimum and maximum values of the axes ALim property (AlphaDataMapping set to scaled, the default).

Transparency mapping method. This property determines how MATLAB interprets indexed alpha data. This property can be any of the following:

• none - The transparency values of AlphaData are between 0 and 1 or are clamped to this range (the default).
• scaled - Transform the AlphaData to span the portion of the alphamap indicated by the axes ALim property, linearly mapping data values to alpha values.
• direct - use the AlphaData as indices directly into the alphamap. When not scaled, the data are usually integer values ranging from 1 to length(alphamap). MATLAB maps values less than 1 to the first alpha value in the alphamap, and values greater than length(alphamap) to the last alpha value in the alphamap. Values with a decimal portion are fixed to the nearest, lower integer. If AlphaData is an array unit8 integers, then the indexing begins at 0 (i.e., MATLAB maps a value of 0 to the first alpha value in the alphamap).

Strength of ambient light. This property sets the strength of the ambient light, which is a nondirectional light source that illuminates the entire scene. You must have at least one visible light object in the axes for the ambient light to be visible. The axes AmbientLightColor property sets the color of the ambient light, which is therefore the same on all objects in the axes.

You can also set the strength of the diffuse and specular contribution of light objects. See the surface DiffuseStrength and SpecularStrength properties.

Face lighting control. This property determines how faces are lit when their vertex normals point away from the camera.

• unlit - face is not lit
• lit - face lit in normal way
• reverselit - face is lit as if the vertex pointed towards the camera

This property is useful for discriminating between the internal and external surfaces of an object. See Back Face Lighting for an example.

Callback routine interruption. The BusyAction property enables you to control how MATLAB handles events that potentially interrupt executing callback routines. If there is a callback routine executing, subsequently invoked callback routines always attempt to interrupt it. If the Interruptible property of the object whose callback is executing is set to on (the default), then interruption occurs at the next point where the event queue is processed. If the Interruptible property is off, the BusyAction property (of the object owning the executing callback) determines how MATLAB handles the event. The choices are:

• cancel - discard the event that attempted to execute a second callback routine.
• queue - queue the event that attempted to execute a second callback routine until the current callback finishes.

Button press callback routine. A callback routine that executes whenever you press a mouse button while the pointer is over the surface object. Define this routine as a string that is a valid MATLAB expression or the name of an M-file. The expression executes in the MATLAB workspace.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

Vertex colors. A matrix containing values that specify the color at every point in ZData. If you set the FaceColor property to texturemap, CData does not need to be the same size as ZData. In this case, MATLAB maps CData to conform to the surface defined by ZData.

You can specify color as indexed values or true color. Indexed color data specifies a single value for each vertex. These values are either scaled to map linearly into the current colormap (see caxis) or interpreted directly as indices into the colormap, depending on the setting of the CDataMapping property.

True color defines an RGB value for each vertex. If the coordinate data (XData for example) are contained in m-by-n matrices, then CData must be an m-by-n-3 array. The first page contains the red components, the second the green components, and the third the blue components of the colors.

On computer displays that cannot display true color (e.g., 8-bit displays), MATLAB uses dithering to approximate the RGB triples using the colors in the figure's Colormap and Dithermap. By default, Dithermap uses the colorcube(64) colormap. You can also specify your own dithermap.

Direct or scaled color mapping. This property determines how MATLAB interprets indexed color data used to color the surface. (If you use true color specification for CData, this property has no effect.)

• scaled - transform the color data to span the portion of the colormap indicated by the axes CLim property, linearly mapping data values to colors. See the caxis reference page for more information on this mapping.
• direct - use the color data as indices directly into the colormap. The color data should then be integer values ranging from 1 to length(colormap). MATLAB maps values less than 1 to the first color in the colormap, and values greater than length(colormap) to the last color in the colormap. Values with a decimal portion are fixed to the nearest, lower integer.

Always the empty matrix; surface objects have no children.

Clipping to axes rectangle. When Clipping is on, MATLAB does not display any portion of the surface that is outside the axes rectangle.

Callback routine executed during object creation. This property defines a callback routine that executes when MATLAB creates a surface object. You must define this property as a default value for surfaces. For example, the statement,

• set(0,'DefaultSurfaceCreateFcn',...
        'set(gcf,''DitherMap'',my_dithermap)')
  

defines a default value on the root level that sets the figure DitherMap property whenever you create a surface object. MATLAB executes this routine after setting all surface properties. Setting this property on an existing surface object has no effect.

The handle of the object whose CreateFcn is being executed is accessible only through the root CallbackObject property, which you can query using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

Delete surface callback routine. A callback routine that executes when you delete the surface object (e.g., when you issue a delete command or clear the axes or figure). MATLAB executes the routine before destroying the object's properties so these values are available to the callback routine.

The handle of the object whose DeleteFcn is being executed is accessible only through the root CallbackObject property, which you can query using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

Intensity of diffuse light. This property sets the intensity of the diffuse component of the light falling on the surface. Diffuse light comes from light objects in the axes.

You can also set the intensity of the ambient and specular components of the light on the surface object. See the AmbientStrength and SpecularStrength properties.

Transparency of the surface edges. This property can be any of the following:

• scalar - A single non-Nan scalar value between 0 and 1 that controls the transparency of all the edges of the object. 1 (the default) is fully opaque and 0 means completely transparent.
• flat - The alpha data (AlphaData) value for the first vertex of the face determines the transparency of the edges.
• interp - Linear interpolation of the alpha data (AlphaData) values at each vertex determine the transparency of the edge.

Note that you must specify AlphaData as a matrix equal in size to ZData to use flat or interp EdgeAlpha.

Color of the surface edge. This property determines how MATLAB colors the edges of the individual faces that make up the surface:

• ColorSpec -- A three-element RGB vector or one of the MATLAB predefined names, specifying a single color for edges. The default EdgeColor is black. See ColorSpec for more information on specifying color.
• none -- Edges are not drawn.
• flat -- The CData value of the first vertex for a face determines the color of each edge.
  
  
• interp -- Linear interpolation of the CData values at the face vertices determines the edge color.

Algorithm used for lighting calculations. This property selects the algorithm used to calculate the effect of light objects on surface edges. Choices are:

• none - Lights do not affect the edges of this object.
• flat - The effect of light objects is uniform across each edge of the surface.
• gouraud - The effect of light objects is calculated at the vertices and then linearly interpolated across the edge lines.
• phong - The effect of light objects is determined by interpolating the vertex normals across each edge line and calculating the reflectance at each pixel. Phong lighting generally produces better results than Gouraud lighting, but takes longer to render.

Erase mode. This property controls the technique MATLAB uses to draw and erase surface objects. Alternative erase modes are useful for creating animated sequences, where control of the way individual objects redraw is necessary to improve performance and obtain the desired effect.

• normal -- Redraw the affected region of the display, performing the three-dimensional analysis necessary to ensure that all objects are rendered correctly. This mode produces the most accurate picture, but is the slowest. The other modes are faster, but do not perform a complete redraw and are therefore less accurate.
• none -- Do not erase the surface when it is moved or destroyed. While the object is still visible on the screen after erasing with EraseMode none, you cannot print it because MATLAB stores no information about its former location.
• xor -- Draw and erase the surface by performing an exclusive OR (XOR) with each pixel index of the screen behind it. Erasing the surface does not damage the color of the objects behind it. However, surface color depends on the color of the screen behind it and is correctly colored only when over the axes background Color, or the figure background Color if the axes Color is set to none.
• background -- Erase the surface by drawing it in the axes' background Color, or the figure background Color if the axes Color is set to none. This damages objects that are behind the erased object, but surface objects are always properly colored.

  Printing with Non-normal Erase Modes

MATLAB always prints figures as if the EraseMode of all objects is normal. This means graphics objects created with EraseMode set to none, xor, or background can look different on screen than on paper. On screen, MATLAB may mathematically combine layers of colors (e.g., XORing a pixel color with that of the pixel behind it) and ignore three-dimensional sorting to obtain greater rendering speed. However, these techniques are not applied to the printed output.

You can use the MATLAB getframe command or other screen capture application to create an image of a figure containing non-normal mode objects.

Transparency of the surface faces. This property can be any of the following:

• scalar - A single non-NaN scalar value between 0 and 1 that controls the transparency of all the faces of the object. 1 (the default) is fully opaque and 0 is completely transparent (invisible).
• flat - The values of the alpha data (AlphaData) determine the transparency for each face. The alpha data at the first vertex determines the transparency of the entire face.
• interp - Bilinear interpolation of the alpha data (AlphaData) at each vertex determine the transparency of each face.
• texturemap - Use transparency for the texturemap.

Note that you must specify AlphaData as a matrix equal in size to ZData to use flat or interp FaceAlpha.

Color of the surface face. This property can be any of the following:

• ColorSpec -- A three-element RGB vector or one of the MATLAB predefined names, specifying a single color for faces. See ColorSpec for more information on specifying color.
• none -- Do not draw faces. Note that edges are drawn independently of faces.
• flat -- The values of CData determine the color for each face of the surface. The color data at the first vertex determines the color of the entire face.
• interp -- Bilinear interpolation of the values at each vertex (the CData) determines the coloring of each face.
• texturemap -- Texture map the CData to the surface. MATLAB transforms the color data so that it conforms to the surface. (See the texture mapping example.)

Algorithm used for lighting calculations. This property selects the algorithm used to calculate the effect of light objects on the surface. Choices are:

• none - Lights do not affect the faces of this object.
• flat - The effect of light objects is uniform across the faces of the surface. Select this choice to view faceted objects.
• gouraud - The effect of light objects is calculated at the vertices and then linearly interpolated across the faces. Select this choice to view curved surfaces.
• phong - The effect of light objects is determined by interpolating the vertex normals across each face and calculating the reflectance at each pixel. Select this choice to view curved surfaces. Phong lighting generally produces better results than Gouraud lighting, but takes longer to render.

Control access to object's handle by command-line users and GUIs. This property determines when an object's handle is visible in its parent's list of children. This property is useful for preventing command-line users from accidentally drawing into or deleting a figure that contains only user interface devices (such as a dialog box).

Handles are always visible when HandleVisibility is on.

Setting HandleVisibility to callback causes handles to be visible from within callback routines or functions invoked by callback routines, but not from within functions invoked from the command line. This provides a means to protect GUIs from command-line users, while allowing callback routines to have complete access to object handles.

Setting HandleVisibility to off makes handles invisible at all times. This may be necessary when a callback routine invokes a function that might potentially damage the GUI (such as evaluating a user-typed string), and so temporarily hides its own handles during the execution of that function.

When a handle is not visible in its parent's list of children, it cannot be returned by functions that obtain handles by searching the object hierarchy or querying handle properties. This includes get, findobj, gca, gcf, gco, newplot, cla, clf, and close.

When a handle's visibility is restricted using callback or off, the object's handle does not appear in its parent's Children property, figures do not appear in the root's CurrentFigure property, objects do not appear in the root's CallbackObject property or in the figure's CurrentObject property, and axes do not appear in their parent's CurrentAxes property.

You can set the root ShowHiddenHandles property to on to make all handles visible, regardless of their HandleVisibility settings (this does not affect the values of the HandleVisibility properties).

Handles that are hidden are still valid. If you know an object's handle, you can set and get its properties, and pass it to any function that operates on handles.

Selectable by mouse click. HitTest determines if the surface can become the current object (as returned by the gco command and the figure CurrentObject property) as a result of a mouse click on the surface. If HitTest is off, clicking on the surface selects the object below it (which maybe the axes containing it).

Callback routine interruption mode. The Interruptible property controls whether a surface callback routine can be interrupted by subsequently invoked callback routines. Only callback routines defined for the ButtonDownFcn are affected by the Interruptible property. MATLAB checks for events that can interrupt a callback routine only when it encounters a drawnow, figure, getframe, or pause command in the routine. See the BusyAction property for related information.

Edge line type. This property determines the line style used to draw surface edges. The available line styles are shown in this table.

Symbol	Line Style
-	solid line (default)
--	dashed line
:	dotted line
-.	dash-dot line
none	no line

Edge line width. The width of the lines in points used to draw surface edges. The default width is 0.5 points (1 point = 1/72 inch).

Marker symbol. The Marker property specifies symbols that display at vertices. You can set values for the Marker property independently from the LineStyle property.

You can specify these markers.

Marker Specifier	Description
+	plus sign
o	circle
*	asterisk
.	point
x	cross
s	square
d	diamond
^	upward pointing triangle
v	downward pointing triangle
>	right pointing triangle
<	left pointing triangle
p	five-pointed star (pentagram)
h	six-pointed star (hexagram)
none	no marker (default)

Marker edge color. The color of the marker or the edge color for filled markers (circle, square, diamond, pentagram, hexagram, and the four triangles).

• none specifies no color, which makes nonfilled markers invisible.
• auto uses the same color as the EdgeColor property.
• flat uses the CData value of the vertex to determine the color of the maker edge.
• ColorSpec defines a single color to use for the edge (see ColorSpec for more information).

Marker face color. The fill color for markers that are closed shapes (circle, square, diamond, pentagram, hexagram, and the four triangles).

• none makes the interior of the marker transparent, allowing the background to show through.
• auto uses the axes Color for the marker face color.
• flat uses the CData value of the vertex to determine the color of the face.
• ColorSpec defines a single color to use for all marker on the surface (see ColorSpec for more information).

Marker size. A scalar specifying the marker size, in points. The default value for MarkerSize is six points (1 point = 1/72 inch). Note that MATLAB draws the point marker at 1/3 the specified marker size.

Row and column lines. This property specifies whether to draw all edge lines or just row or column edge lines.

• both draws edges for both rows and columns.
• row draws row edges only.
• column draws column edges only.

MATLAB -generated or user-specified normal vectors. When this property is auto, MATLAB calculates vertex normals based on the coordinate data. If you specify your own vertex normals, MATLAB sets this property to manual and does not generate its own data. See also the VertexNormals property.

Surface's parent object. The parent of a surface object is the axes in which it is displayed. You can move a surface object to another axes by setting this property to the handle of the new parent.

Is object selected? When this property is on, MATLAB displays a dashed bounding box around the surface if the SelectionHighlight property is also on. You can, for example, define the ButtonDownFcn to set this property, allowing users to select the object with the mouse.

Objects highlight when selected. When the Selected property is on, MATLAB indicates the selected state by drawing a dashed bounding box around the surface. When SelectionHighlight is off, MATLAB does not draw the handles.

Color of specularly reflected light. When this property is 0, the color of the specularly reflected light depends on both the color of the object from which it reflects and the color of the light source. When set to 1, the color of the specularly reflected light depends only on the color or the light source (i.e., the light object Color property). The proportions vary linearly for values in between.

Harshness of specular reflection. This property controls the size of the specular spot. Most materials have exponents in the range of 5 to 20.

Intensity of specular light. This property sets the intensity of the specular component of the light falling on the surface. Specular light comes from light objects in the axes.

You can also set the intensity of the ambient and diffuse components of the light on the surface object. See the AmbientStrength and DiffuseStrength properties. Also see the material function.

User-specified object label. The Tag property provides a means to identify graphics objects with a user-specified label. This is particularly useful when constructing interactive graphics programs that would otherwise need to define object handles as global variables or pass them as arguments between callback routines. You can define Tag as any string.

Class of the graphics object. The class of the graphics object. For surface objects, Type is always the string 'surface'.

Associate a context menu with the surface. Assign this property the handle of a uicontextmenu object created in the same figure as the surface. Use the uicontextmenu function to create the context menu. MATLAB displays the context menu whenever you right-click over the surface.

User-specified data. Any matrix you want to associate with the surface object. MATLAB does not use this data, but you can access it using the set and get commands.

Surface normal vectors. This property contains the vertex normals for the surface. MATLAB generates this data to perform lighting calculations. You can supply your own vertex normal data, even if it does not match the coordinate data. This can be useful to produce interesting lighting effects.

Surface object visibility. By default, all surfaces are visible. When set to off, the surface is not visible, but still exists and you can query and set its properties.

X-coordinates. The x-position of the surface points. If you specify a row vector, surface replicates the row internally until it has the same number of columns as ZData.

Y-coordinates. The y-position of the surface points. If you specify a row vector, surface replicates the row internally until it has the same number of rows as ZData.

Z-coordinates. Z-position of the surface points. See the Description section for more information.

surface

surfl