v.random: create true 3D vector in the example, add image for the example

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63389 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.random/v.random.html

@@ -35,11 +35,25 @@ Generate 20 random points with binary attribute (only 0 or 1):
 v.random output=binary_random n=20 zmin=0 zmax=1 column='binary INTEGER'
 </pre></div>
 
-Generate 20 random 3d points with height attribute [0:20] and specific random seed:
+Generate 20 random 3D points using a specific random seed:
 <div class="code"><pre>
-v.random seed=501 output=height_random n=20 zmin=0 zmax=1 column=height
+v.random seed=52 output=height_random npoints=40 zmin=110 zmax=170 -z
 </pre></div>
 
+<p>
+<center>
+<img src="vrandom_z.png"><br>
+Random points with different X, Y, and Z coordinates
+</center>
+
+<!--
+g.region rast=elev_lid792_1m
+...
+d.vect height_random color=60:60:60 icon=basic/point size=40 width=2 zcolor=gyr
+optipng -o5 map.png
+mv map.png vrandom_z.png
+-->
+
 Get 20 random samples from raster map:
 <div class="code"><pre>
 g.region -p rast=elevation