### Using hierarchy

If in the param section of a .rt file exist attribute buildhier with value 1, then the program will use an hierarchy for speedup the creation of the image.

If it is the first time that it loads the .rt file (for example demo.rt) then the program creates an hierarchy and save it in a file with extension .rt_ and the same name ( it will be demo.rt_ in the example). The next time you load the file to create the image, it will find the saved file and load the hierarchy without creation.

If you have changed some object, or added or deleted, you may encounter an error or a wrong image; in this case you should delete the .rt_ file.

You should not delete the file if you change a section different from object section.