zfail single pass shadow volumes and patents

I’m curious about shadow volumes, so I was looking here and around on the Web for documentation about that, and was finding a website talking about patents on the zfail approach:

The patent situation well and truly sucks.

We were prepared to use a two-pass algorithm that gave equivalent results at a speed hit, but we negotiated the deal with Creative so that we were able to use the zfail method without having to actually pay any cash. It was tempting to take a stand and say that our products were never going to use any advanced Creative/3dlabs products because of their position on patenting gaming software algorithms, but that would only have hurt the users.

John Carmack

It’s dated about one year now, but it seems the patent comes from 2002, by Creative Labs.

What is strange is that we can find out almost everywhere about this technique (but only the 2 passes is explained) and almost noone is talking about this patent. If I’m not wrong, the single pass comes from using some specific extensions under gl (nv stencil two sides or so).

What do we, gl programmers, can risk if we implement this technique ? Is that patent still alive or has it fall down when Id decided to promote some Creative technologies ?

Presumably the patent still stands.
Unless the patent is unnecessarily broad (which it doesn’t sound like) or you can find prior art, there is no way to get rid of a patent - other than its expiry (in 20 years or so).

Any deal id made with Creative would be limited to them only.
Usually licensing requires paying money (or even royalties), but in this case Creative accepted something else in return for the use of their algorithm. So I suppose they’re open to alternatives.

This patent is valid only in the US ( and some few other countries ) or am I wrong? So I think that in france you can use this alghoritm without permission of creative…

Thanks God the european parliament voted against patents at tuesday! :slight_smile: So feel free to use every patented algorithm you can find :smiley:

Just 2 days ago the european government decided against a patenting law, which had allowed trivial algorithms to be patented, such as in the US.


I’m under Linux everyday, have had heard about that since years, but didn’t knew that… anyway, thank you for that.

Originally posted by Zengar:
Thanks God the european parliament voted against patents at tuesday! :slight_smile: So feel free to use every patented algorithm you can find :smiley:
I also followed this with a lot of interest ad happiness at the end.
As for the others which are not as lucky as we are, I’ve made some reasearch on the topic.

Given facts: mail from JC himself to NVIDIA dated may 23 2000, still avaiable on nVIDIA’s developer relationship website.
Patent from Creative labs filed October 13, 1999. Search from USPO by using keywords as “zfail”, “stencil”, “volume” and possibly others, will stand 20 years.
Fact: looks like Creative sued ID when they recognized they would not have supported EAX natively.

I won’t say what I think on the issue because those are mainly personal opinions. I think you can check it yourself.

As for me, referring to an article recently appeared on Game Developer Magazine on prior art (see http://kwiki.ffii.org/SwpatcninoEn, WW news or the magazine’s archive website), I must say US should think twice on patents and try to recover, provided this is possible.