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This page covers everything about the nature of meshes and specialities used in The Sims 3.



Mesh of an living chair

A mesh is a grid in 3D space which forms a shape and is mainly used for displaying textures on it. Vertices (points) are joined together to create the Polygons (faces). A Normal is attached in a certain angle to each vertex to shade the mesh properly.


Vertices selection
When modeling a new object, there are several 'modes' in which you can mesh. 'Vertex' is one of these modes. Vertex is simply a point on a mesh (See the picture to the right for reference)

Unlike polygons or faces, a vertices selection mode can be used to pull that point out.

Vertex Count

The Vertex/Vertices count on an object determines how detailed it is. You may think 'Ah, great - go wild with vertices' but this isn't the case..

The higher vertices count an object has, the slower it makes the game run when that object is placed. There are rough guidelines for the vertex count of each object, a guide to how many verts it should have, for example, a 2-seater sofa like the one displayed in the picture should have around 1,000 - 1,500 vertices.


A quad, composed of two triangles. Each triangle is a face.

A face (or polygon) is a 2D shape that, when put together with others, will form a 3D mesh. A polygon can contain any number of edges - however, The Sims 3 (or more specifically, Milkshape) can only support polygons with 3 sides - called triangles. Many 3D applications create meshes with polygons that have 4 sides - called quads, and a few programs allow you to create polygons with any number of sides that you want - called NGons.

All of these types of polygons are fine to model with, Milkshape will automatically convert all the faces to triangles - if possible. Quads can be divided into two triangles, so there are no problems there. When using NGons, however, not every NGon will return an even number of triangles, and thus such faces will disappear.

A sphere, composed of triangles. Each triangle is a polygon

When put together, multiple polygons can be moved around to form any shape desired. Polygons by themselves are not visible, (nor are vertices or edges) they are sort of like... a rule. You know they are there, but you can't see them. What you CAN see however, is the material that is applied to the polygons via the UV Map.

Faces Count

Each polygon on your mesh requires a small amount of computer resources to display. The more polygons that you have in a mesh, the more computer power is required to display it.

Don't go too high!

If a player is heavily furnishing a house with a lot of high polygon content, it can have adverse effects on their game and computer. The game can crash, and their PC can overheat if it gets to be too much, which could utimately result in video card fans working too hard and dying, resulting in the card itself overheating and dying. It could happen to your computer too, if you are extensively testing your own high polygon creations. Remember: higher polygons = higher computing power. Try to stay low!

When creating for The Sims 3, you need to keep in mind the amount of polygons that you are using. Meshes that have to be rendered in "Real time", as do meshes in The Sims 3, lower polygons generally results in better game performance.

While there is no set rule or limit about how many polygons you can use, generally I think most creators will agree that with most people getting newer, faster computers all the time, roughly 1200 polygons per tile is acceptable, depending on the object. If it's going to be rarely used in a house, you can go a little higher. If it's something like a dinning chair and there are going to be multiples all around, you should try to stay lower.

Also, the bigger the object, the more polygons you can use. For example: A double bed. 6 tiles. 1200 x 6 = 7200. This would include the bedding, which is a couple thousand itself, so you have to keep that in mind. A two tile couch would be 2400 polygons total.

Keeping Track!

To make it easier to keep an idea in your head of what an acceptable polygon count is, base the figure on 1000 polygons per tile, rather than 1200. If you know you are working with a 3 tile object, for example, make note that the polygon count stays around 3000. This way will also give you a little leeway incase you happen to go over.

UV Map

A simple UV layout of a 3D cube
A UV Map is a set of planar coordinates that, when applied to a mesh, will assign each face to a certain area of the texture. Simply put, it tells the mesh where the textures should be applied.

UV Maps are represented in 2D space, where U and V replace the 3D coordinates X and Y. Each vertex is assigned a "UV", which are connected into faces in much the same way the 3D mesh is.

Why are UV Maps important?

A Mesh with proper texture and proper UV Map
A Mesh with proper texture but horrible UV Map

As already stated, a UV map controls what part of a texture is assigned to what part of a mesh. This controls the entire look of the object! If you don't take time and care to properly UV Map your mesh:

  • Faces will randomly be blurry/sharp, because the scale is isn't consistent
  • When in game, patterns will be rotated in random directions and wont line up
  • Patterns on some faces will be much larger/smaller than other parts
  • Some faces may have the same texture, while others may have the completely wrong texture

A simple dresser mesh, with proper texture and UV Map, versus what happens when the UV Map is wrong. Faces are the wrong way, at odd angles, etc. Granted, you COULD make a proper texture for a UV Map like this, once in game, it would look horrible with patterns applied to it.

Ways to UV Map a mesh

Most programs come with several standard ways to map a mesh. They generally include:

  • Planar - A projection based on an axis. This face is mapped based on the camera being on a the X axis, whereas this other face is mapped from above on the Y axis. The axis usually corresponds to the direction the face is facing. Good for planes, can be used for advanced mapping of other shapes.
  • Cube/Box Map - A variation of planar, it automatically maps everything from one of the 3 axis based on where the faces are facing. Good for cubes, boxes, etc. Anything that is relatively square.
  • Cylinder - It "unfolds" the mesh so that you get one consistent strip for the body of the cylinder rather than lots of individual faces that aren't lined up. Can work on cubes, generally recommended for things that cylindrical.
  • Sphere - Another method that kind of "unfolds" the mesh, it's designed for things that are round. Not very useful unless you are mapping a sphere.

Automatic Mapping

Some higher end programs include options for "Automatic Mapping", and as the name suggests, it automatically decides how each face should maped and lays them out on the UV Map in a concise, consistent way.

UV Mapping Utilities

Most 3D applications have some built in method of dealing with UV Maps. Some programs are more advanced than others, and they are all different in some way.

Milkshape 3D has a very, very basic UV Mapper built in. It's so simple that it's almost impossible to use. You can only map by group, and each group can only be planar mapped from one axis. UV Mapping within Milkshape requires a lot of work and patience!

Almost every other 3D program has a basic UV Mapping utility that can map based on the different projections mentioned earlier. Higher end programs such as 3D Studio Max and Maya are generally more advanced than lower end programs such as Wings 3D and Milkshape.

External UV Mapping

There are a couple of programs out there that are only for UV Mapping.

  • UV Mapper - Classic and Pro. Classic is free and fairly basic. You have to buy the Pro version, but it is more advanced.
  • LithUnWrap - Free, fairly advanced utility that can be used with good results.
  • Blender 3D - While not strictly for UV Mapping, Blender3D has exceptional UV Mapping capabilities for a free program, although it is somewhat difficult to learn.

Level of Detail (LOD)

A Mesh in The Sims 3 has one or more lower detail meshes. The game requires these to display the whole neighborhood. The farer away a mesh is it gets switched into a lower detail mesh. This depends a lot on the performance of a computer when the switch is going to happen. The Very High LOD is only used in CAS because there it doesn't need to display the whole neighborhood. Between High LOD, Medium LOD and Low LOD the game always checks if it can switch to a higher detail or needs to switch to a lower detail mesh.


If you are doing a mesh you absolutely need to create the extra lower detail meshes! Importing the same mesh in all LOD slots is a NO GO! The game relies to having the aibility to switch to lower detail meshes to run smoothly, or to run at all.



LODs of a clothing mesh


LODs of a hair mesh


LODs of an object mesh


Morphs are only required for CAS creations. Objects don't use them. You have two or more identical meshes, but some of the vertices are in slightly different locations on one of the morphs. The game then blends these morphs together to create various states, such as fit and fat for your sims.

No New Data!

A morph can only contain moved vertices! You can not add vertices, faces, or edges. Only move them!

How Morphs Work

Thin morph compared to the fat morph of the same mesh

Morphs are primarily used in for Create-A-Sim content such as hair and clothing. For example, a shirt has several morphs. There is the base mesh, but then there are also morphs for thin, fit, fat, and pregnant states.

When a sim is "fit", the game uses the "fit" mesh. As a sim gets "fat", it slowly changes to the "fat" mesh. It's not a sudden change - it's a slow morph. The "fit" mesh gets blended with the "fat" mesh and all of the states in between are based on using a certain percentage of one mesh combined with a certain percentage of the other.

The list of morphs in Milkshape

When a sim is getting fat, but not actually "fat", the game will display a mesh that is the "fit" version halfway morphed to the "fat" version - which results in the sim being somewhere between "fit" and "fat", but without actually being either.

How Do I Create Morphs?

Because a morph only contains data for moved vertices, you must base your morph off of the original mesh. Duplicate your base mesh, and by only using Move/Scale, adjust it to fit the criteria of whatever morph you are making.

Milkshape only!

Morphs are found in Create-A-Sim content, which is animation-heavy. Because each morph needs to retain it's joint information, you need to keep the morph meshes in Milkshape - otherwise you will have to reassign all the joints over again - and they will have to be assigned identically to the original mesh!

Three Morphs in Milkshape: Thin, Normal, and Fat.

If you are working on the pregnant morph, make the mesh how it should appear on pregnant sims. If you are making a shirt, for example, you would almost completely change the entire shape - versus a hair mesh, which wouldn't really need any change at all.

If you want, you can base morphs off of morphs. If you have already created a fat morph and are now working on the pregnant morph, you can duplicate the fat morph and modify it into the pregnant morph.

Once all morphs have been created, you need to make sure they are renamed to match the original morph names, so that the game knows they are actually morphs and not just extra meshes.

How do I know if I made my morphs correctly?

In Workshop, under the "Mesh" tab, there are a couple of sliders. You can slide these back and forth to view how your mesh will morph between states. If something looks wrong, head back to Milkshape and work on it some more.

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