surface_properties

Description

The Surface entity is a leaf of the graphics entities hierarchy. Two classes appears under this type of entity : Plot3d and Fac3d according to the ploting function or the way data is entered. Fac3d and Plo3d entities are similar but Fac3d is more complete and accept more options than Plot3d. To always have Fac3d entities, simply use genfac3d to pre-build matrices before using plot3d or use the surf command.

Here are the properties contained in a surface entity:

parent:

This property contains the handle of the parent. The parent of the surface entity should be of type "Axes" or "Compound".

children:

This property contains a vector with the children of the handle. However, surface handles currently do not have any children.

visible:

This field contains the visible property value for the entity . It should be "on" or "off" . By default, surfaces are visibles, the value's property is "on". If "off" the 3D graphics are not displayed on the screen.

surface_mode:

This field contains the default surface_mode property value for the surface. Its value should be "on"(surface drawn) or "off" (no surface drawn).

foreground:

If color_mode >= 0, this field contains the color index used to draw the edges. If not, foreground is not used at all. The foreground value should be an integer color index (relative to the current colormap).

thickness:

This property is a positive real specifying the width of facets contours in pixels. The displayed width is actually determined by rounding the supplied width to the nearest integer. The only exception is vectorial export where the whole thickness value is considered.

mark_mode:

This field contains the default mark_mode property value for the surface. Its value should be "on" (marks drawn) or "off" (no marks drawn).

mark_style:

The mark_style property value is used to select the type of mark to use when mark_mode property is "on". The value should be an integer in [0 14] which stands for: dot, plus, cross, star, filled diamond, diamond, triangle up, triangle down, diamond plus, circle, asterisk, square, triangle right, triangle left and pentagram.The figure below shows the aspects of the marks depending on the mark_style and the mark_foreground and mark_background properties.

mark_size_unit:

This field contains the default mark_size_unit property value. If mark_size_unit is set to "point", then the mark_size value is directly given in points. When mark_size_unit is set to "tabulated", mark_size is computed relative to the font size array: therefore, its value should be an integer in [0 5] whith stands for 8pt, 10pt, 12pt, 14pt, 18pt and 24pt. Note that plot3d and pure scilab functions use tabulated mode as default ; when using the surf (or plot for 2D lines) function, the point mode is automatically enabled.

mark_size:

The mark_size property is used to select the type of size of the marks when mark_mode property is "on". Its value should be an integer between 0 and 5 whith stands for 8pt, 10pt, 12pt, 14pt, 18pt and 24pt.

mark_foreground:

This field contains the mark_foreground property value which is the marks' edge color. Its value should be a color index (relative to the current color_map) or 0 for transparant edge.

mark_background:

This field contains the mark_background property value which is the marks' face color. Its value should be a color index (relative to the current color_map) or 0 for transparant face.

data:

This field defines a tlist data structure of type "3d" composed of a row and column indices of each element as the x-, y- and z-coordinates contained respectivly in data.x,data.y and data.z. The complementary field named data.color is available in case a real color vector or matrix is specified. If none, data.color is not listed. The surface is painted according to color_modeand color_flag properties.

color_mode:

an integer between [-size(colormap) ; size(colormap)] defining the color of the facet when color_flag value is 0. As stated before, ifcolor_mode > 0, edges are drawn using foreground color. If color_mode is set to 0, a mesh of the surface is drawn: front faces have no colors. Finally, when color_mode < 0, front faces are painted with color -color_mode but no edges are displayed.

color_flag:

This field is used to specify the algorithm used to set facets' colors.

Not that the rules on color_mode, foreground and hiddencolor are still applied to this case.

• color_flag == 0

  • All facets are painted using the color index and method defined by color_mode (see above).

• color_flag == 1

  • All facets are painted using one color index per facet proportional to z. The minimum z value is painted using the index 1 color while the maximum z value is painted using highest color index. The edges of the facets can be additionnaly drawn depending on the value of color_mode (see above).

• The 3 remaining cases (color_flag== 2,3 or 4) are only available only with Fac3d entity. Then, the data.color value is used to set colors for facets (indices in the current colormap) if it exists. If not, the current color_mode is used to paint the facets.

• color_flag == 2 ('flat' shading)

  • All facets are painted using the color index given in the data.color property (one color per facet is needed). Two cases are then possible :

  • data.color contains a color vector : if color(i) is positive it gives the color of facet i and the boundary of the facet is drawn with current line style and color. If color(i) is negative, color id -color(i) is used and the boundary of the facet is not drawn.

    data.color contains a color matrix of size (nf,n) where n stands for the number of facets and nf for the number of points defining the polygonal facet. For the nf vertices defining each facet, the algorithm computes an average value of the color index (from the matrix color index) : the nf vertices of the same facet will have the same color index value.

• color_flag == 3 ('interpolated' shading)

  • Facets painting results of interpolation of vertices colors. The indices of vertices color are given in the data.color property (one color per vertex is needed). Two cases are possible :

  • data.color contains a colors vector : then, there are too few data to complete the interpolated shading mode. Indeed, a color matrix of size (nf,n) (where n stands for the number of facets and nf for the number of points defining the polygonal facet) is needed to perform this operation. For each facet, the algorithm copies the single color index value of the facet into the nf color indexes vertices defining the facet's boundary.

    data.color contains a color matrix of size (nf,n) (see upper for nf and n definitions), the interpolated shading mode can be completed normally using those color indexes.

• color_flag == 4 (Matlab-like 'flat' shading)

  • Same as color_flag==2 with a slight difference when data.color is a matrix. All facets are painted using the color index given in the data.color property (one color per facet is needed). Two cases are then possible :

  • data.color contains a color vector : if color(i) is positive it gives the color of facet i and the boundary of the facet is drawn with current line style and color. If color(i) is negative, color id -color(i) is used and the boundary of the facet is not drawn.

    data.color contains a color matrix of size (nf,n) where n stands for the number of facets and nf for the number of points defining the polygonal facet. For the nf vertices defining each facet, the algorithm takes thecolor of the first vertex defining the patch (facet).

cdata_mapping:

Specific to Fac3d handles. A string with value 'scaled' or 'direct'. If a data.color is set, each index color data specifies a single value for each vertex. cdata_mapping determines wether those indices are scaled to map linearly into the current colormap ('scaled' mode) or point directly into this colormap ('direct' mode). This property is usefull when color_flag equals 2,3 or 4.

hiddencolor:

This field contains the color index used to draw the backward faces of a surface. Its value should be a positive integer (color index relative to the current colormap). If it is a negative integer,the same color than the "visible" face is applied to the rear face.

clip_state:

This field contains the clip_state property value for the surface. It should be :

• "off" this means that the surface is not clipped.

• "clipgrf" this means that the surface is clipped outside the Axes box.

• "on" this means that the surface is clipped outside the rectangle given by property clip_box.

clip_box:

This field is to determinate the clip_box property. By Default its value should be an empty matrix if clip_state is "off". Other cases the vector [x,y,w,h] (upper-left point width height) defines the portions of the surface to display, however clip_state property value will be changed.

user_data:

This field can be use to store any scilab variable in the surface data structure, and to retreive it.

Examples

//create a figure 
t=[0:0.3:2*%pi]'; z=sin(t)*cos(t');
[xx,yy,zz]=genfac3d(t,t,z); 
plot3d([xx xx],[yy yy],list([zz zz+4],[4*ones(1,400) 5*ones(1,400)])) 
h=get("hdl") //get handle on current entity (here the surface) 
a=gca(); //get current axes
a.rotation_angles=[40,70]; 
a.grid=[1 1 1]; 
//make grids 
a.data_bounds=[-6,0,-1;6,6,5];
a.axes_visible="off"; 
//axes are hidden a.axes_bounds=[.2 0 1 1]; 
f=get("current_figure");
//get the handle of the parent figure 
f.color_map=hotcolormap(64); 
//change the figure colormap 
h.color_flag=1; 
//color according to z 
h.color_mode=-2; 
//remove the facets boundary 
h.color_flag=2; 
//color according to given colors 
h.data.color=[1+modulo(1:400,64),1+modulo(1:400,64)];
//shaded
h.color_flag=3; 

scf(2); // creates second window and use surf command
subplot(211)
surf(z,'cdata_mapping','direct','facecol','interp')

subplot(212)
surf(t,t,z,'edgeco','b','marker','d','markersiz',9,'markeredg','red','markerfac','k')
e=gce();
e.color_flag=1 // color index proportional to altitude (z coord.)
e.color_flag=2; // back to default mode
e.color_flag= 3; // interpolated shading mode (based on blue default color because field data.color is not filled)

See Also

• set — set a property value of a graphic entity object or of a User Interface object.
• get — Retrieve a property value from a graphics entity or an User Interface object.
• delete — delete a graphic entity and its children.
• plot3d — 3D plot of a surface
• plot3d1 — 3D gray or color level plot of a surface
• plot3d2 — plot surface defined by rectangular facets
• surf — 3D surface plot
• graphics_entities — description of the graphics entities data structures

Authors

Djalel ABDEMOUCHE & F.Leray