Garry's Mod has a copy-protection trap that shows this error:

Unable to shade polygon normals

It made me wonder if such a problem could ever actually exist. Can polygon normals be shaded? Is a failure to do so detectable and reportable?

  • \$\begingroup\$ This is actually an interesting question. \$\endgroup\$ Jun 17, 2011 at 17:36
  • \$\begingroup\$ I'd love to know what causes this message because its kind of insane. \$\endgroup\$
    – wangburger
    Jun 17, 2011 at 17:39
  • 3
    \$\begingroup\$ The message wasn't a real error, it was an anti copy protection bit-tech.net/news/gaming/2011/04/13/… - A lot of people were banned from the official forums that day :) \$\endgroup\$
    – Elva
    Jun 17, 2011 at 17:47
  • 2
    \$\begingroup\$ @Yourdoom, yup. Keep in mind no one got their steam account or Gmod account banned. Only people who pirated the game had their account on the forum banned. There were 2 false positives in the first 30 minutes of the patch, but Garry checked their steam profiles(the error message contained their steam ID) and confirmed they did own GMOD. \$\endgroup\$ Jun 17, 2011 at 17:52
  • \$\begingroup\$ I'm voting to close this question as off-topic because it's not about a game's error message. \$\endgroup\$ Aug 9, 2015 at 0:35

3 Answers 3


"Can a polygon normal be shaded" - No, a normal is a vector which is a 1-d object, so unless you're going to actually draw the normal and shade it, that statement doesn't make much sense.

However, shading polygons (2-d objects) commonly use the polygon normal in their shading calculations for light calculations to control how light or dark they can be.

So, I have no idea what that message is trying to say.

  • 4
    \$\begingroup\$ -1 cause Normals are 3D objects, vectors, usually normalized and represent a line perpendicular to the surface they are associated with. The rest of the info us more or less accurate though. \$\endgroup\$
    – James
    Jun 17, 2011 at 23:43
  • 1
    \$\begingroup\$ I think you misunderstood what I was getting at. Any normal will appear as a 1-d object (line) since there is length only along 1 axis. Also, don't get stuck thinking that normals always have 3 components. \$\endgroup\$
    – wangburger
    Jun 18, 2011 at 0:54
  • \$\begingroup\$ 1D is a point 2D is a line, normals are actually a 3D vector though representing the line perpendicular to the surface they are associated with ;) And due to computer hardware, most normals actually have 4 components but that does not really matter I suppose. Anywho, turns out the correct answer to this question is that people who see it pirated Gary's Mod... Sooo.. yeah :) \$\endgroup\$
    – James
    Jun 20, 2011 at 17:51
  • \$\begingroup\$ Nope. 1D is a line, 2D is a plane, 3D is a cube. \$\endgroup\$ Jan 16 at 3:48

Normals in 3D graphics are a 3D vector indicating orientation or direction.

Normals themselves cannot be shades, as how can you shade {.1,0,.4} ?

Normals can be used to shade the polygons themselves. For example, a light source at a certain angle hitting a model made of polygons at a certain angle, the normals of the polygon faces can be used in the shading process to make the light make parts of the model brighter.

  • \$\begingroup\$ +1 for good explanation of Normals. While I am not a person who has used Gary's mod, I would suggest that the message seen is a feature detection method stating they can not support normal map shading, either in general or for a specific object.. Again, just a guess though. \$\endgroup\$
    – James
    Jun 17, 2011 at 23:44

It's 100% not possible to shade a normal at all.

As discussed in this link from the comments, the message was chosen to stop people from being able to research it, to tempt them into asking about it, and outing themselves as pirates.

This was counting on players not knowing what a polygon normal actually was. :)

  • \$\begingroup\$ That's pretty superb as a piracy canary. It would help improve this answer if you substantiate this with citations. \$\endgroup\$ Apr 30, 2021 at 23:07
  • \$\begingroup\$ en.wikipedia.org/wiki/Normal_(geometry) \$\endgroup\$ Apr 30, 2021 at 23:31
  • \$\begingroup\$ I mean, citing the part about Garry's Mod using the error to indicate this. It makes perfect sense you can't shade a normal—it doesn't have a surface—but the Garry's Mod claim is another thing. It's one thing for a claim to have truthiness; citation helps establish it as true. \$\endgroup\$ May 1, 2021 at 15:47
  • \$\begingroup\$ Already cited in the OP. \$\endgroup\$ May 2, 2021 at 14:16
  • \$\begingroup\$ The citation is in the comments; since comments don't last as long as answers, I've added the same link into your answer. This way if the comments get cleaned up / cleared out at some later date, the information will still be here. \$\endgroup\$
    – Pikalek
    May 3, 2021 at 2:24

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