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Displaying Complex Three-Dimensional Objects

This example shows how to create and display a complex three dimensional object and control its appearance.

Get Geometry of Object

This example uses a graphics object called the Newell teapot. The vertex, face, and color index data for the teapot are calculated by the teapotData function. Since the teapot is a complex geometric shape, there are a large number of vertices (4608) and faces (3872) returned by the function.

[verts, faces, cindex] = teapotGeometry;

Create Teapot Patch Object

Using the geometry data, draw the teapot using the patch command. The patch command creates a patch object.

p = patch('Faces',faces,'Vertices',verts,'FaceVertexCData',cindex,'FaceColor','interp')

p = 
  Patch with properties:

    FaceColor: 'interp'
    FaceAlpha: 1
    EdgeColor: [0 0 0]
    LineStyle: '-'
        Faces: [3872x4 double]
     Vertices: [4608x3 double]

  Use GET to show all properties

Use the view command to change the orientation of the object.

view(-151,30)     % change the orientation
axis equal off    % make the axes equal and invisible

Adjust Transparency

Make the object transparent using the FaceAlpha property of the patch object.

p.FaceAlpha = 0.3;   % make the object semi-transparent

If the FaceColor property is set to 'none', then the object appears as a wire frame diagram.

p.FaceColor = 'none';    % turn off the colors

Change Colormap

Change the colors for the object using the colormap function.

p.FaceAlpha = 1;           % remove the transparency
p.FaceColor = 'interp';    % set the face colors to be interpolated
p.LineStyle = 'none';      % remove the lines
colormap(copper)           % change the colormap

Light the Object

Add a light to make the object appear more realistic.

l = light('Position',[-0.4 0.2 0.9],'Style','infinite')
l = 
  Light with properties:

       Color: [1 1 1]
       Style: 'infinite'
    Position: [-0.4000 0.2000 0.9000]
     Visible: on

  Use GET to show all properties

lighting gouraud

These properties of the patch object affect the strength of the light and the reflective properties of the object:

  • AmbientStrength - controls the strength of ambient light

  • DiffuseStrength - controls the strength of diffuse light

  • SpecularStrength - controls the strength of reflected light

  • SpecularExponent - controls the harshness of reflected light

  • SpecularColorReflectance - controls how reflected color is calculated.

You can set these properties individually. To set these properties to a predetermined set of values that approximate the appearance of metal, shiny, or dull material, use the material command.

material shiny

Adjust the position of the light using its Position property. The position is in x, y, z coordinates.

l.Position = [-0.1 0.6 0.8]

l = 
  Light with properties:

       Color: [1 1 1]
       Style: 'infinite'
    Position: [-0.1000 0.6000 0.8000]
     Visible: on

  Use GET to show all properties