Probably because you have two edges coming from the same vertex. Add another vertex to the right and connect that down instead. Dissolve or delete the existing edge.
You can look up poles, they are often inevitable and useful, but can generate pinching on curved surfaces.
There's 3 kinds of poles;
An N-pole is when you have 3 edges connecting to the vertex, which creates uneven pulling of the surface in one direction. An E-pole has 5 or more edges connecting to a surface and often creates pinching. This is why we generally want to go for quad-poles. 4 edges per vertex, like in most of your mesh.
You can either have the diagonal line run straight up, or route it down the curve of your vehicle, be careful not to create too uneven polygons.
https://preview.redd.it/0bdp20ct468d1.jpeg?width=132&format=pjpg&auto=webp&s=7fe53b0a5d49302cb5892d317a14ab4fd2f19588
but this does have a quad pole, i don't understand?
its natural on low poly because you have [this](https://www.reddit.com/user/namespace_object/comments/1dmjv48/sample/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button).
always use loop tools if you want a smooth shading or deleted those face and use grid fill.
https://preview.redd.it/7ot5o3ufv78d1.png?width=776&format=png&auto=webp&s=a089fe6b24b385b52990385c5488f021deffec46
Try something like this? That's too low poly for a long diagonal cut on a curve surface.
If you absolutely need it to be that low poly then look up data transfer mod.
data transfer mod doing its thing.
https://preview.redd.it/11uapo9zz78d1.png?width=1827&format=png&auto=webp&s=1fc4cd3549687b8366fc9ef6fdefb5b55d6337d3
using normal data from this uncut mesh.
https://preview.redd.it/bch524d6088d1.png?width=1823&format=png&auto=webp&s=64e1e19c7184a608c28f4c332cca220fd502d8b7
The worst spot is obviously following a specific edge, so start playing with that edge to see what helps. I'd probably begin with dissolving it just to see what happens, sometimes an ngon can still smooth out just fine. Then you can try some alternative edge solutions, like redirecting it moving vertically like the other nearby edge loops, and/or placing a tri where the corner of the window ends, stuff like that.
In my experience this might be the result of weird vectors? Id first try to select all, alt+n then reset vectors. This happened to me because my vectors were split for some reason.
When this happens to me i usualy clear the custom Slpit Normals Data, if you wnt to try it, is in the green vertex icon, in geometry data, there are three options, try deletong the custon Split if theres any
Probably because you have two edges coming from the same vertex. Add another vertex to the right and connect that down instead. Dissolve or delete the existing edge.
You can look up poles, they are often inevitable and useful, but can generate pinching on curved surfaces. There's 3 kinds of poles; An N-pole is when you have 3 edges connecting to the vertex, which creates uneven pulling of the surface in one direction. An E-pole has 5 or more edges connecting to a surface and often creates pinching. This is why we generally want to go for quad-poles. 4 edges per vertex, like in most of your mesh. You can either have the diagonal line run straight up, or route it down the curve of your vehicle, be careful not to create too uneven polygons.
https://preview.redd.it/0bdp20ct468d1.jpeg?width=132&format=pjpg&auto=webp&s=7fe53b0a5d49302cb5892d317a14ab4fd2f19588 but this does have a quad pole, i don't understand?
He's talking about the vertex to the top left of that. There are 5 edges coming off it.
Was doing this 20 years ago. Drove me nuts and the resources online were pretty much non existent. Good old 3DS Max days.
In my experience normals can just get fucked up randomly, I always try and just reset the normals first. Hit Alt+N > Reset normals
its natural on low poly because you have [this](https://www.reddit.com/user/namespace_object/comments/1dmjv48/sample/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button). always use loop tools if you want a smooth shading or deleted those face and use grid fill.
i called it distorted planar. Planar should flat as possible.
Are you using any modifiers?
nope
https://preview.redd.it/7ot5o3ufv78d1.png?width=776&format=png&auto=webp&s=a089fe6b24b385b52990385c5488f021deffec46 Try something like this? That's too low poly for a long diagonal cut on a curve surface. If you absolutely need it to be that low poly then look up data transfer mod.
Terrible pinching https://preview.redd.it/rqkn4g7qz78d1.png?width=1861&format=png&auto=webp&s=eae178c54227bddabb03d2d10153c0545d4f92f5
data transfer mod doing its thing. https://preview.redd.it/11uapo9zz78d1.png?width=1827&format=png&auto=webp&s=1fc4cd3549687b8366fc9ef6fdefb5b55d6337d3
using normal data from this uncut mesh. https://preview.redd.it/bch524d6088d1.png?width=1823&format=png&auto=webp&s=64e1e19c7184a608c28f4c332cca220fd502d8b7
The worst spot is obviously following a specific edge, so start playing with that edge to see what helps. I'd probably begin with dissolving it just to see what happens, sometimes an ngon can still smooth out just fine. Then you can try some alternative edge solutions, like redirecting it moving vertically like the other nearby edge loops, and/or placing a tri where the corner of the window ends, stuff like that.
In my experience this might be the result of weird vectors? Id first try to select all, alt+n then reset vectors. This happened to me because my vectors were split for some reason.
When this happens to me i usualy clear the custom Slpit Normals Data, if you wnt to try it, is in the green vertex icon, in geometry data, there are three options, try deletong the custon Split if theres any
EXACTLY THIS!!!!! Blender 4 has had this bs shading issue since they changed it.
You can also check normals