3-D Visualization

Adding Lights to a Scene

This example displays the membrane surface and illuminates it with a light source emanating from the direction defined by the position vector [0 -2 1]. This vector defines a direction from the axes origin passing through the point with the coordinates 0, -2, 1. The light shines from this direction towards the axes origin.

• membrane
  light('Position',[0 -2 1])
  

Creating a light activates a number of lighting-related properties controlling characteristics, such as the ambient light and reflectance properties of objects. It also switches to Z-buffer renderer if not already in that mode.

Illuminating Mathematical Functions

Lighting can enhance surface graphs of mathematical functions. For example, use the ezsurf command to evaluate the expression

over the region -6 to 6.

• ezsurf('sin(sqrt(x^2+y^2))/sqrt(x^2+y^2)',[-6*pi,6*pi])
  
  
  
  
  

Now add lighting using the lightangle command, which accepts the light position in terms of azimuth and elevation.

• view(0,75)
  shading interp
  lightangle(-45,30)
  set(gcf,'Renderer','zbuffer')
  set(findobj(gca,'type','surface'),...
      'FaceLighting','phong',...
      'AmbientStrength',.3,'DiffuseStrength',.8,...
      'SpecularStrength',.9,'SpecularExponent',25,...
      'BackFaceLighting','unlit')
  
  
  

After obtaining surface object's handle using findobj, you can set properties that affect how the light reflects from the surface. See the "Properties That Affect Lighting" section of this chapter for more detailed descriptions of these properties.

Light Objects

Properties That Affect Lighting