public void setGravity(float x, float y, float z) {
        this.gravity.x = x;
        this.gravity.y = y;
        this.gravity.z = z;
    }
Sets the gravity vector.

@param x the x component of the gravity vector
@param y the y component of the gravity vector
@param z the z component of the gravity vector
jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java