LE 3DS Max render to texture is barfing up a malformed normal map

[Madcat221]

I discovered that my attempt to avoid extra work concerning UVWing a dagger that is largely the same UVW as a sword has failed, and I will need to re-bake the blade for it. Since it's just the blade, and it's a wholly separate hull that's not welded to the hilt, I decided to re-bake just the blade and splice in the re-UVW'd part. Furthermore, since the shorter length cleared out some UVW real estate, I decided what the hey, have the two sides be separate instead of overlapping.

 

I follow the steps I have before to render to texture. I have my hi-poly slightly larger than the low-poly. I set up the projection cage, I set up the normal map texture element to render, I assign the file name and type, I set it to render to the Bump map slot, I pick my resolution, click "output into normal bump", and hit Render.

 

And it vomits up this. :sick:

 

 

 

What am I doing wrong? :psyduck: I've done this before, I generated the original normal maps. And yet this is what comes out!

[Madcat221]

Well, I found the original source meshes that I baked from and just re-did it from them with a corrected UVW. It'd still be nice to know what this is indicative of, though.

[KorinOo]

I think one of the models has flipped normals.

 

If you take the closer look, you can see that the geometry of surface details was baked ok, so the problem is with the colors used to define this geometry. In normal maps, different colors are responsible for different directions, and such an extreme result indicate that there is a big difference in surface directions between low poly and high poly (and flipped normals basically counts as "opposite direction").