Hi there! It can be a graphics card issue, but not necessarily. It can also be a problem with smoothing groups in Blender (or another 3D editor), which is a common problem.
So actually it can be one of those problems:
1. Graphics card - sometimes also relates to lines in Sims' faces and CAS-objects
2. Grouping in Blender - relates to lines in objects, like the ones you see in your chair.
I suggest you try option 2 first, as making changes to your graphics card driver is probably more difficult and also tricky to test.
In general if you see the lines you mentioned in S4Studio, you will also see them ingame. So S4Studio is a quick testing environment for any solutions.
For 2. see this tutorial: tutorial - also mentioned as the solution in this
post. You can also check this
video.
For me (nvidia GTX970, drivers updated, Win10 on Core i7) this worked for problem 2.
The general idea of making smoothing groups is to select sharp edges, mark them as seams and split your mesh over these edges (P / Selection). Blender will automatically adjust the smoothing for those selections. After making the selections and separating them, select them all and join them with Ctrl + J. This will give a single object with several smoothing groups.
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Edit: if you use Blender 2.76 or higher, you don't have to split and rejoin your mesh, as this adds extra faces.
Select your mesh in Blender, then in the navigator click the Mesh tab and look for the Normals roll menu. See
this picture.Check Auto Smooth and change the value at Angle to fit your smoothing needs. All faces with angles below the selected value will be in the same Auto-smooth group. This way smoothing can be applied while the amount of faces stays the same. Here is a very short and simple
video to illustrate this. It might not work on very complicated meshes however.
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Blender and other 3D editors simply cannot calculate the correct smoothing and lighting for every part of a mesh and this is a way to guide the smoothing process.
Your mesh certainly has sharp edges, like the sides of the chair base and the sides of the chair legs. Make seams at the base of the legs to create a smoothing group for each leg and so on. Do a few legs, test it and if the lines are gone you know this solution works for you.
If you use smoothing groups on objects that need weight transfer (like CAS-objects) then do the regrouping BEFORE weight transfer. The regrouping operation will seriously interfere with previous weight transfers and cause problems.
Making seams in your mesh is also of great help with UV-mapping. You can UV-map the separate parts, which is much easier.
Tip: it can often be useful to UV unwrap twice, the first time as Lightmap Pack and the second time as Follow Active Quads (both on exactly the same selection). This will give you a nice and straightened UV-map which you can easily bring into the right position.
Hope this will help!
Happy Simming!
