Add particle system for drops hitting the ground (better in SVN for future).

It needs to be called by code, like the rain textured cylinders.


git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7701 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/gfx/rain-ground.xml

@@ -0,0 +1,40 @@
+<?xml version="1.0"?>
+<!--
+  Particle system to simulate it's raining heavily in the ground.
+  Current tests done as kart particles, but this should be per camera
+  and placed like the cylinders that have rain drop textures, maybe
+  with some speed compensation, so it never wastes particles (out
+  of view) when camera moves really fast. Then rate can be trimmed
+  down to 150/180 or 100/120, with smaller box.
+-->
+<particles emitter="box" box_x="12.0" box_y="0.5" box_z="12.0">
+
+    <spreading angle="20"       />
+    
+    <velocity  x="0.000"
+               y="0.005"
+               z="0.000"         />
+    
+    <material  file="water-splash.png"  />
+    
+    <!-- Amount of particles emitted per second -->
+    <rate      min="200"
+               max="240"         />
+    
+    <!-- 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>