UV trickery
polycounter lvl 7
Hey guys. I chanced on this model on Artstation and noticed something very interesting on the UVs. It appears they have planar projected the red handle of the flaregun and the black grip as one piece(but not the actual edges that I have shown with an arrow in the last picture.. This is very confusing to me as i would have thought there would be shading issues? I would normally move the black grip UV shell to the away from the handle(this takes up more room on the UVs)
You can see in the 3D model and UVs that the actual sides of the black grip are UV'd separately. Just wondering how this is done. I would have thought there would be projection issues? I noticed that the grip is also welded to the handle for some reason(they share verts) rather than just sitting on top. Is this to help in the baking process?Thanks heaps.
You can see in the 3D model and UVs that the actual sides of the black grip are UV'd separately. Just wondering how this is done. I would have thought there would be projection issues? I noticed that the grip is also welded to the handle for some reason(they share verts) rather than just sitting on top. Is this to help in the baking process?Thanks heaps.
Replies
UV seams are not a problem for baking normal maps, really. There are some technical bits to be careful with, but it doesn’t stop you from pretty much adding seams wherever you like.
This is by Polycount member @Emalphi who might shed some light on how this was made.
I think the grip is just a planar projection, the edge strip was then detached and UV'd separately into a rectilinear strip. Then the UVs for the handle and grip are not welded, that's just an open seam that is in the same location. I marked those overlapped edges here in red:
Usually you would want to add some UV space between the grip and the rest of the gun, to prevent texture filtering from bleeding across the edges. It's just so minor here that it's not a big deal.
It's a bit odd though that there's no UV padding above the rectilinear strip, where I marked it with green above. Here's a closeup:
The gutter color above it is from the UV island above, it doesn't match the top of the strip. I'm guessing that's why there's a bit of a bleed in the normal map here.
Anyhow, once it's textured and lit, you can't really see the artifacts unless you zoom in close. If this was a smooth shiny metal, it would really show up though.
As to why there's no red handle under the black grip, it's usually best to remove unseen triangles. Reduces UV waste, and improves antialiasing since there aren't two nearby surfaces being resolved via the z-buffer. A bit more about why that helps: http://wiki.polycount.com/wiki/Normal_Map_Modeling#Contiguous_Meshes
As far as I'm concerned this is completely normal behaviour
Assuming it's been executed well, there should be no visible difference once the model is far enough away for the silhouette of the handle to be insignificant
It's usually better when the lower LODs can re-use the same texture, because this allows the game to use less textures, which improves rendering performance (faster load times, faster render-prep, less stalling during rendering, etc.).
Learn about MIPs: http://wiki.polycount.com/wiki/Mip_Mapping
More about LODs, including more poopipe because everyone likes more poo from the pipe
For instance the asset may have gone through a round of outsourcing and this detail wasn't caught during review ; or perhaps, they had a pipeline involving building a clean ingame low first (with tertiary details baked or generated later) taken care of by someone with great modeling skills but only basic knowledge of good practices for baking/texturing. Or maybe a junior took care of the UVs and tried too hard to save space. Who knows !