Bump mapping was supposed to be a selling point of the Gamecube hardware, so it wouldn't surprise me if Nintendo specifically asked or told Factor 5 to incorporate it.
IIRC, it was used in the Zelda Spaceworld 2000 demo. I remember magazines at the time noting the bump mapping on Ganondorf's sword:
At the time, hardware bumpmapping was an inconsistent mess, and despite lofty promises, they didn't end up delivering what was promised. It wasn't until the "bump map" was torn down and replaced with the "normal map" in 1999 by Kilgard that the stage was set for the future. I suspect that they stopped talking about it to distance themselves from that association. The specific hardware feature in the GameCube was also getting retooled, and the "bump texture" unit eventually turned into the much more powerful "indirect texture" unit, and that thing is a beast. It was used everywhere, as it should have been. If you've seen my video on displacement maps [0], the indirect texture unit was what powered that.
Nintendo reused bumpmapping in a few places in Luigi's Mansion, but their primary trick was spherical-mapped environment mapping, which they basically mastered the art of. They also later developed a way of using the indirect texture unit to do normal mapping on the Wii, though I believe that tech was only used in a few places in Wii Sports Resort.
I think the article itself probably explains it well: you didn't get it for free.
>However, there was a reason this effect didn't take off until years later. The DirectX9 and newer forms of bump mapping are painless - developers can use them with very little setup and they are very, very cheap to run. Devs don't even need to think about it. But with this older type of bump mapping, developers had to build the effect themselves. And it was not cheap. For something that just adds a bit of visual flare, most GameCube and Wii developers decided it was not worth it and passed it by.
So again, Nintendo themselves probably coded it into the tech demo because they wanted to show off what was possible with the hardware, even if it wasn't practical (I believe there was a Dreamcast tech demo that bragged about how many polygons they had put into rendering a bowl of fruit).[0] And it is known that Nintendo worked with Factor 5 directly to provide them with prototype Gamecube hardware before the console was ready so that F5 could release a "killer app" launch title. It wouldn't surprise me, then, that F5 similarly threw in all the bells and whistles they could think of.
IIRC, it was used in the Zelda Spaceworld 2000 demo. I remember magazines at the time noting the bump mapping on Ganondorf's sword:
https://www.youtube.com/watch?v=SvE3yJv3fm0
Slightly longer video of just the Zelda segment:
https://www.youtube.com/watch?v=RIa79bTDuV4