Particle.j3md now supports shadow casting (only for triangle-based particles)

jme3-core/src/main/resources/Common/MatDefs/Misc/Particle.frag

@@ -19,4 +19,12 @@ void main(){
     #else
         gl_FragColor = color;
     #endif
+
+    #ifdef PRE_SHADOW
+        if (gl_FragColor.r <= 0.1 && 
+            gl_FragColor.g <= 0.1 &&
+            gl_FragColor.b <= 0.1) {
+            discard;
+        }
+    #endif
 }

jme3-core/src/main/resources/Common/MatDefs/Misc/Particle.j3md

@@ -63,6 +63,29 @@ MaterialDef Point Sprite {
         }
     }
 
+    Technique PreShadow {
+
+        VertexShader   GLSL100 : Common/MatDefs/Misc/Particle.vert
+        FragmentShader GLSL100 : Common/MatDefs/Misc/Particle.frag
+
+        WorldParameters {
+            WorldViewProjectionMatrix
+            WorldViewMatrix
+            WorldMatrix
+            CameraPosition
+        }
+
+        Defines {
+            USE_TEXTURE : Texture
+            PRE_SHADOW
+        }
+
+        ForcedRenderState {
+            DepthWrite On
+            ColorWrite Off
+        }
+    }
+
     Technique SoftParticles{
 
         VertexShader   GLSL100 : Common/MatDefs/Misc/SoftParticle.vert