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ATTN ALL, question about Dark Radiant & professional use

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The reason ID worked around the Carmarck's Reverse patent is very specific: when you make a GPL release, the license requires that you grant a patent license for any patent which might cover the code. Since this was a known patent which was not owned by ID, they could not legally grant this license, and therefore had to remove the patented algorithm from the code before making the GPL release.

I don't think they were particularly worried about being sued by Creative, otherwise they would have removed it from their closed-source code long before the GPL release (or maybe they negotiated a commercial license with Creative, which covered the commercial Doom 3 but not any subsequent GPL releases).

Note that some people have said that the Creative patent is actually invalid, and as far as I know it has never actually been taken to court, so this whole thing is something of a theoretical risk (a bit like open-source implementations of FAT which are widely used despite possibly infringing patents by Microsoft).

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The creative patente has expired https://patents.google.com/patent/US6384822B1/en  imo no need to worry about if is invalid or not.

But based on this quote from dhewm3 engine using the "Carmarck's Reverse" trick will not bring better performance. :( 

  • This neither seems to make a visual nor performance difference on any hardware I tried (including Raspberry Pi 4), so this is mostly out of principle.


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For Doom 3 vanilla, most relatively recent hardware will see no difference with Carmack's reverse.

TDM has Carmack's reverse since we have much higher poly models and larger scenes with more shadow casters.

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Please visit TDM's IndieDB site and help promote the mod:




(Yeah, shameless promotion... but traffic is traffic folks...)

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