public Matrix4f mult(Matrix4f in2) {
        return mult(in2, null);
    }
Right-multiply by the specified matrix. (This matrix is the left factor.)

@param in2 the right factor (not null, unaffected)
@return the product, this times in2 (a new instance)
jme3-core/src/main/java/com/jme3/math/Matrix4f.java