# 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:

  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_mode` and `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, if`color_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.

  Note 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 additionaly 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 the`color 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 useful 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.

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 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
- get
- delete
- plot3d
- plot3d1
- plot3d2
- surf
- graphics_entities