surface transparency

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<P>Hello, All</P>
<P>I used Gridded2DSet to draw a topography surface. I&nbsp;also want to draw 
some street&nbsp;lines on the surface. Each street line has some points with 
only x and y, I used valueToInterp method to interpolate these points to get z 
values, then draw these points as one line.&nbsp;My problem is,&nbsp;some 
segment of the line are below the surface. So I want&nbsp;my topography surface 
to be transparent so that every thing below the surface can be seen clearly. I 
tried the following:</P>
<P>dispGMC = 
<P>zMap&nbsp;&nbsp;&nbsp;= new ScalarMap(Z, 
Display.RGB);<BR>display.addMap(zMap);<BR>display.addMap(new ScalarMap(Z, 
<P>Now the surface I got is opaque. I do not know how to set the Alpha 
<P>Any help will be highly appreciated.</P>
<P>Gaoming Fu</P></DIV>
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