public static ParticleMesh buildParticles(
     String name, int number, ParticleSystem.ParticleType particleType) {
   if (particleType != ParticleSystem.ParticleType.Triangle
       && particleType != ParticleSystem.ParticleType.Quad)
     throw new IllegalArgumentException(
         "particleType should be either ParticleSystem.ParticleType.TRIANGLE or ParticleSystem.ParticleType.QUAD");
   ParticleMesh particleMesh = new ParticleMesh(name, number, particleType);
   ParticleController particleController = new ParticleController(particleMesh);
   particleMesh.addController(particleController);
   return particleMesh;
 }
 public static ParticleMesh buildMeshParticles(String name, TriMesh mesh) {
   ParticleMesh particleMesh = new ParticleMesh(name, mesh);
   ParticleController particleController = new ParticleController(particleMesh);
   particleMesh.addController(particleController);
   return particleMesh;
 }