3-D Visualization

Selecting an Alphamap

An alphamap is simply an array of values ranging from 0 to 1. The size of the array can be either m-by-1 or 1-by-m.

The default alphamap contains 64 values ranging linearly from 0 to 1, as you can see in the following plot.

• plot(get(gcf,'Alphamap'))
  
  
  

This alphamap displays the lowest alpha data values as completely transparent and the highest alpha data values as opaque.

The alphamap function creates some useful predefined alphamaps and also enables you to modify existing maps. For example,

• plot(alphamap('vup'))
  

produces the following alphamap.

You can shift the values using the increase or decrease options. For example,

• alphamap('increase',.4)
  

adds the value .4 to all values in the current figure's alphamap. Replotting the 'vup' alphamap illustrates the change. Note how the values are clamped to the range [0 1].

• plot(get(gcf,'Alphamap'))
  
  
  

Example: Mapping Data to Color or Transparency

Example: Modifying the Alphamap