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surface properties

description of the 3D entities 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 plotting 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:

"on" (default): The surface is displayed, possibly with its mesh and markers.
"off" : The surface and its mesh and markers are hidden.

surface_mode:

"on" (default): facets (body and edges) are drawn.
"off" : facets (body and edges) are hidden. But markers -- if any -- are still displayed (provided that .mark_mode = "on").

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 20]. 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] which 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 which 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 transparent 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 transparent 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 respectively 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:

color index in [-size(colormap), size(colormap)]

If color_flag == 0 : The uniform color of the whole upward surface is set to the index abs(color_mode).

In addition, whatever is color_flag,

color_mode = 0 makes facets hollow and displays only the surface's mesh.
color_mode > 0 displays facets bodies and edges.
color_mode < 0 hides the mesh and displays only facets bodies.

When it is displayed, the mesh color is set to foreground.

color_flag:

Chooses the algorithm used to set the color of the body of the upward face of facets, when it is displayed.

In addition,

color_mode rules the display of the mesh (facets edges) and/or body of facets.
foreground and thickness rules the line color and thickness of the mesh.
hiddencolor rules the color of the backward facets face.

Here below,

nf stands for the number of facets of the surface.
n stands for the number of vertices of each facet. All facets have the same number of vertices.

Then we have:

color_flag = 0 (uniform color) :

All facets are painted using the same color index and method defined by color_mode (see above).
color_flag = 1 (uniform color on each facet, mapping Z) :

The average Z of each facet is computed according to the Z of its vertices. Then the [Zmin, Zmax] range of facets Z is computed. Each facet gets its uniform color in [1, size(colormap)] according to its Z position in [Zmin, Zmax].

color_flag== 2,3 or 4 values are only available with Fac3d entities. These algorithms require the data.color input to set facets colors. If data.color is empty, the color_flag=1 fallback algorithm is used.

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 :
1. data.color is a vector of as many color indices as there are facets, color(i) being the color index for the facet #i :
  - color(i)>0: the boundary of the facet is drawn with current line style and color.
  - color(i)<0: the facet's boundary is not drawn, and -color(i) is used as facet's color.
2. data.color is a matrix of color indices, of size (n,nf). Then, the actual color index of the facet is set to the average color of all its vertices.

color_flag = 3 (interpolated shading on each facet) :

Facets painting is done by interpolating their 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 is a vector of nf color indices, color(i) being the index of the flat uniform color of the facet #i.

data.color is a color matrix of size (n,nf): The facet #i is drawn with some graded colors interpolated between the color(:,i) colors of its vertices.

If the Z coordinate of vertices has been assigned to data.color, this mode allows to map local Z with colors, down to the facet scale. See also the .cdata_mapping property.

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

Same as color_flag==2, except that, when data.color is a color matrix, each facet #i is painted with the uniform color(1,i) of its first vertex (instead of the average color of all its vertices). Other vertices colors are ignored.

cdata_mapping:

'scaled' or 'direct'. Used only for color_flag=2|3|4 (Fac3d handles), with some data.color defined. Otherwise ignored.

"direct": data.color values are directly considered as color indices in the current gcf().color_map.
"scaled": c=data.color values are linearly mapped on the interval [1,nC], with nC=size(gcf().color_map,1) is the total number of colors in the current colormap. Then, min(c) represents the color #1, and max(c) represents the color #nC.

hiddencolor:

Positive index of the color of the uniform backward faces of all facets. If a negative or null value is provided, backward faces are painted with the same respective colors as the upward visible ones.

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.

use_color_material:

This field is use to enable the use of the surface color as diffuse color. Its default value is "on".

material_shininess:

This field defines the shininess level of the surface. This parameter controls the shinines color spreading in the surface. Any positive value can be used. Good values to use are in the [0 10] range, where low values generates strong highlight and high values generates barely perceptible highlights. The default value is "2".

ambient_color:

This field defines the ambient color of the surface. The color is defined by a 3 element vector "[red, green, blue]" with each element in the range [0, 1]. The default value is "[1 1 1]".

diffuse_color:

This field defines the diffuse color of the surface. The color is defined by a 3 element vector "[red, green, blue]" with each element in the range [0, 1]. Notice that this field is only used when use_color_material is disabled. The default value is "[1 1 1]".

specular_color:

This field defines the specular color of the surface. The color is defined by a 3 element vector "[red, green, blue]" with each element in the range [0, 1]. The default value is "[1 1 1]".

user_data:

This field can be use to store any scilab variable in the surface data structure, and to retrieve 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=hot(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)

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