Face-weighted normals kind of broke for these inset panels and their bevels, so I had to tweak the resulting normals, try different methods, etc. Still not perfect, but in the end it was good enough for what I needed.
On a thing like this car hood detail I would rather make all normals same , borrowed /transferred using normal theft/ data transfer or whatever from a surface before all those extra ridges added and keep their shading in the normal map only . Would work perfect for LODs too.
oh brilliant! Thanks, that is definitely useful. I spoke to my teacher, and he said you have to cut the uvs if there is a bevelled edge. What does he mean by this, and where do you cut if there are bevelled edges? Apparently, it does something to the normals to make a better bake. How do i know what way the normals should be facing and how do i know if its shooting in the wrong direction?
You have been so great; I just want to ask another question: On a model some of the pieces are mirrored to the other side. I want to achieve high resolution by making use of much of the space in the UV layout. Do you include the mirrored geometry on the UV layout; for example, if I was modelling a car with 4 wheels, would you put 4 wheels on the UV layout or just 1 to maximise UV layout space, because it's a duplicate, or do you layout everything?
You need to split UV edge when you split vertex normals along an edge (i.e make the edge "hard" or in 3d max terms set different smooth group in adjacent faces. For a videocard it's no difference would you just split the geometry ) Beveled edge on the other hand allows you to keep smooth shading across it. So unified vertex normals along the edge . Id est non necessarily having UV splits . So its other way around. You probably misread your teacher. Or they offer you very inefficient way to avoid baking skew issues multiplying vertex count of your model tremendously.
Beveled edges could perfectly exist inside UV islands . Hard/split/ edges or borders of smooth groups in 3d max terms needs corresponding splits in UVs.
Sometimes you still may have UV island border along beveled edge. In such case you can split /make hard the edge having UV seam but not necessarily.
What modern 3d soft offer is "face waiting" of beveled edges . When vertex normals alone both edges of a bevel are rotated to be perpendicular to adjacent bigger face. It keeps shading gradient within thin bevel and eliminates it from bigger adjacent faces.
To see vertex normals you can use edit normal modifier in 3d max or or mesh edit mode viewport overlay in Blender. ( Blender calls them "split normals", middle button in mesh edit viewport overlay)
If the vertex normals are split (making a hard edge on the low-poly), then you usually need to split the UVs too, and add empty UV space between the two islands.
Bevels do not require UV splits, in general. There are exceptions, so ask them to explain the “why” behind their rules.
cturbo about duplicating details it's up to you. For a car it's perfectly ok to have only one wheel in UV . Be careful with mirroring . Better to be done on mesh level using special Mirror /symmetry or whatever. Mirror modifier in Blender e.g . Doing it on object level which often is just negative scaling may cause issues with flipping normals and mismatching tangent /bi-normal vectors against baked normal map ? Although I had little to no such issues in modern software for a while.
Perhaps it's just Blender behavior. When you select an object and do mirror X I suspect it just scales it negatively. Showing and rendering it just fine with correct normals within Blender.
But when you export the mesh its normals are getting inverted. So I use mirror modifier and two vertex group with _L and _R suffixes to delete redundant part later by GN modifier.
When you select an object and do mirror X I suspect it just scales it negatively. Showing and rendering it just fine with correct normals within Blender.
Yes. So after mirroring one should remember to Apply Scale, and flip the normals.
Replies
https://github.com/KhronosGroup/glTF-Sample-Assets/blob/451f96783f5a4b32895616f2f5f98e12d877be9f/Models/SunglassesKhronos/README.body.md#modeling-with-face-weighted-normals
Left to right in the image above:
Basically if you can afford the extra vertex cost of bevels, then you should probably use face-weighted normals.
But it depends on the surfaces, sometimes face-weighted doesn't work great, if you have some organic-shaped surfaces. For example the interior of the car hood here: https://github.com/KhronosGroup/glTF-Sample-Assets/pull/159
Face-weighted normals kind of broke for these inset panels and their bevels, so I had to tweak the resulting normals, try different methods, etc. Still not perfect, but in the end it was good enough for what I needed.
Mirroring and duplication are explained a bit here http://wiki.polycount.com/wiki/Normal_Map_Modeling
Yes, wheels are a great candidate for duplication/reuse.
I recently did a normal trick for wheels, might help you: