Add alpha threshold for shadow casting.

files/shaders/shadowcasting_fragment.glsl

@@ -14,4 +14,8 @@ void main()
         gl_FragData[0].a = texture2D(diffuseMap, diffuseMapUV).a * alphaPassthrough;
     else
         gl_FragData[0].a = alphaPassthrough;
+
+    // Prevent translucent things casting shadow (including the player using an invisibility effect)
+    if (gl_FragData[0].a < 0.5)
+        discard;
 }