When it comes to creating game assets, there is no such thing as "subjectively wrong" or "subjectively right". The developers created a system and your job as a cc creator is to make sure your item is adapted to function as intended by
them. To know how it should be adapted, you need to clone a similar maxis item and study it. This - studying a maxis item - is something the author of the tutorial you had a misfortune of watching either has never done themselves before recording it or did not think of mentioning because pretty much everything is done wrong.
When making a dress, start a package from a dress of similar length, not anything else. Your dress is affected by skirt bones but the item you cloned was not, hence the problem
The mesh distorts where the skirt bones are, this is your clue.
You cloned a nude upper body to start a package. The nude upper body has no skirt, thus is not affected by skirt bones, they are not present in the package.
You are not creating a package from scratch, you are replacing Geometry and texture resources in the duplicate of a maxis package. For this reason, you need to clone something that is the closest to yours in shape, the closest in the intended functionality.
Other issues, unrelated to the problem at hand:
1). The sims 4 is an 8 yo game that can be played on a very low performance machine. To make it possible, maxis almost never makes content that goes beyond 10k tris. In your case the buttons alone have 6,2k. You won't even see them up close to appreciate the details, so this increase in the polycount serves no purpose at all. You need to either
retopologize them or just use a custom low poly one.
If you were to quadrangulate a maxis item and look at its topology, you'd notice that the vertices are placed and connected in a specific way instead of randomly like in your case.
This is called an edge flow and it is responsible for how the mesh is shaded and how it functions:
- in the breast area the topology is more dense and the edge loops have circular shape. This allows the breast to expand and shrink in the correct shape, smoothly;
- there are edge loops in places the mesh is meant to bend(elbows, armpits, knees, groin);
- in places where the mesh does not need to bend or expand the topology is less dense.
MD offers a
good manual retopology tool but i would not recommend a beginner to dive right into the logic behind retopology. For now just model in
quads and do not lower Particle distance too much.
2). Export the garment from md with these settings, without including materials, blender cannot render them.
3). Do not import the garment in a blank scene. Clone something similar in shape, export it, open it, join all parts of it together, rename to Reference. Import the garment there.
4).Transfer all data from the reference with these exact settings. Right now the skirt area is not vertex painted with the correct color and the vertices there are affected by too many bones
5). When closing holes, extrude
and collapse. This will reduce the polycount of the created geometry in half
How to close holes:
- Switch to Edit mode ( TAB ), switch to Edge select ( 1 ), select the border edge loop ( 2 ) by Alt-RMB-clicking on it;
- Press E to extrude, S to scale, scale it down ( 3 );
- Press Alt M and choose Collapse ( 4 );
- Switch to Vertex select, select the vertex in the middle of created geometry, optionally move it up a bit, press Shift NumPad7 to align the view parallel to it;
- Select - Select More/Less - More ( 5 );
- Shading / UVs - UV Mapping - Unwrap - Project from view* ( 6 );
- In UV editor scale it down ( S ) and put somewhere in the extra area;
- Select the same border edge again and mark it as Sharp ( 7 );
- before baking textures, select one edge marked as sharp, Select - Select similar - Sharpness, then split all of them with Mesh - Edges - Edge split.
6). If you were to look at uv_0 and the diffuse of a reference , you'd see:
- that the uvs are in the space meant for tops and bottoms. Yours are in
the shoes area as well, which results in conflicts with shoes;
- the uvs are not stretched vertically, yours are. UVs that were created in the square uv space will stretch when rectangular textures are applied. Before re-arranging them, you must shrink them back to the original size by selecting all with A and pressing S X 0.5;
- outside of uvs there is a margin, a few pixels of texture. Your diffuse does not have this, so you see those skin-colored strips all over the item;
- the uvs do not overlap. When a body part's and a garment's uvs overlap like in your case, the body displays the garment's textures.
7). Maxis items have no overlapping geometry. All parts of the body covered by clothing must be deleted. All parts of the clothing covered by another piece of clothing must be deleted as well. This will prevent clipping and free up the uv space;
8). As mentioned before, split sharp edges before baking textures or importing the garment in s4s;
9). Do not clone nude body parts, some of them come with a buff that makes sims embarrassed when other see them.