Example -- Modifying the Alphamap :: Transparency (3-D Visualization)

3-D Visualization

Example -- Modifying the Alphamap

This example uses slice planes to examine volume data. The slice planes use the color data for alpha data and employ a rampdown alphamap (the values range from 1 to 0):

Create the volume data by evaluating a function of three variables.

[x,y,z] = meshgrid(-1.25:.1:-.25,-2:.2:2,-2:.1:2);
v = x.*exp(-x.^2-y.^2-z.^2);

Create the slice planes, set the alpha data equal to the color data, and specify interpolated FaceAlpha.

h = slice(x,y,z,v,[-1 -.75 -.5],[],[0]);
alpha('color')
set(h,'EdgeColor','none','FaceColor','interp',...
    'FaceAlpha','interp')

Install the rampdown alphamap and increase each value in the alphamap by .1 to achieve the desired degree of transparency. Specify the hsv colormap.

alphamap('rampdown')
alphamap('increase',.1)
colormap(hsv)

This alphamap causes the smallest values of the function (around zero) to be displayed with the least transparency and the greatest values to display with the most transparency. This enables you to see through the slice planes, while at the same time preserving the data around zero.

Selecting an Alphamap Creating 3-D Models with Patches