Add XML for heavy rain effect, see comments at top.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7674 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/gfx/rain.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0"?>
+<!--
+  Particle system to simulate it's raining heavily over an item/kart.
+  It should be applied no matter if kart is flying or on (any) ground,
+  and rotate to always fire up, it just simulates the rain bouncing
+  off the kart and being fired by wheels. It could also be applied to
+  bowling balls, for example.
+-->
+<particles emitter="box" box_x="0.5" box_y="1.0" box_z="1.0">
+
+    <spreading angle="10"       />
+    
+    <velocity  x="0.000"
+               y="0.009"
+               z="0.000"         />
+    
+    <material  file="water-splash.png"  />
+    
+    <!-- Amount of particles emitted per second -->
+    <rate      min="50"
+               max="60"         />
+    
+    <!-- Minimal and maximal lifetime of a particle, in milliseconds. -->
+    <lifetime  min="1000"
+               max="1000"         />
+    
+    <!-- Size of the particles -->
+    <size      min="0.35"
+               max="0.70"        />
+
+    <color     min="255 255 255"
+               max="255 255 255" />
+
+    <!-- How much time in milliseconds before the particle is fully faded out  -->
+    <fadeout   time="750"        />
+
+    <gravity   strength="-0.01"
+               only-force-time="500" />
+</particles>