Prop Asset Creation

It's recommended to stay within reasonable triangle counts based on the size and detail of your model. You may look at examples of vanilla props or assets by other creators for reference.

The absolute limit for a mesh is 65536 vertices.

Triangle counts of some vanilla props.

LOD stands for level of detail. This is the mesh visible from a distance. It must be as simple as possible. Props are usually very small so a model with 1-6 triangles could be enough.

If you don't provide an LOD mesh, the game will try to generate one automatically, which may have visual issues, so it's highly recommended to make a custom LOD mesh.

Comparison between main and LOD meshes for the vanilla grill kiosk.

For the main mesh, you are allowed to UV map outside the 0-1 area (main tile), so you can tile the entire texture multiple times on a single face.

Example UV mapping using visible horizontal tiling on the bottom.

For the LOD mesh, the UV mapping must be within the 0-1 area (main tile) of the UV map, no tiling is allowed. This is because ingame all the LOD textures are combined into a single texture called an atlas, so having incorrect uv mapping will end up putting the texture of some other random prop on your LOD.

UV mapping for LOD mesh using automatic mapping in 3ds Max. No overlap and contained within the main tile - good for baking.

The vertex color blue channel determines snow behavior on winter maps - 0 means no snow will be visible.

Vertex colors are also used for specific shaders like AnimUV for scrolling or multi-frame animations, or PropRotating for rotating animations.

Vertex painting in 3ds Max.

Prop culling is when a prop disappears when you look away from the center of it.

If your prop has a low height or is wide/long, it's recommended to add an invisible triangle which is bigger than your actual mesh to make the game think the prop is larger than it actually is, which will reduce the chance of it disappearing.

Infinitely thin triangles made by putting 2 of the 3 vertices in the same place.

All imported main textures must be the same resolution.

Powers of 2 is a standard practice in 3D graphics, which means resolutions such as 1024x1024, 1024x512, 256x512, 2048x128 etc. It is recommended to stick to this standard, otherwise, your texture may be corrupted by compression, which may be more visible at longer distances or grazing angles. The smallest allowed resolution is 32x32.

Texture sizes of various vanilla assets. See the resolution in the top right corner of the preview window.

The main color and texture of your asset.

It will look very bright, contrasty, and saturated in the game, so make sure to reduce the saturation and limit the brightest parts to a medium/light gray below 140 RGB.

If you don't import a diffuse map, it will default to white.

Transparency, white means opaque or visible, black means transparent or invisible. Gray values may affect how it looks from a distance or at an angle.

Semi-transparency is not supported, you need to use the rotors shader for that.

If you don't import an alpha map, it will default to fully opaque or fully visible.

Allows for diffuse contribution illumination. Black means no illumination and white means the brightest possible illumination.

There are parameters for blinking illumination or disabling illumination during the day.

If you don't import an illumination map, it will default to no illumination.

Example illumination map for a torch.

Reflectivity, black means no reflection and white means max reflection.

The specular highlight from the sun is very big and bright, so you might want to use very low (0-10%) specularity for surfaces facing upwards.

If you don't import a specular map, it will default to no specularity.

Also sometimes called a bump map, adds fake depth or form by affecting how the lighting appears.

This can be made from the diffuse or a height map (brighter colors will look extruded out more) using a normal map generator online , a photoshop plugin like xNormal , or standalone software such as CrazyBump .

The normal map generator should be set to +X +Y, which means no color channel inversions are required. Read more in the normal map article .

High specularity and normal map don't work well together because of the compression, so you might want to paint over shiny parts with a solid color before generating a normal map or paint over these parts 128,128,255 on the final normal map.

If you don't import a normal map, it will default to a flat normal map - no bump.

You should place the mesh and texture files in the import folder located here:

%LocalAppData%\Colossal Order\Cities_Skylines\Addons\Import

The AppData folder is hidden by default, you can access it by copying and pasting the path into the file explorer, or pressing Windows + R and typing in appdata.

Files ready for import.

After you choose your mesh, depending on how it was exported, you might need to set the correct scale and rotation, scale 100 and rotating 3 times around X-axis are common necessities.

Importing a mesh in asset importer.

Various things can be changed with the use of ModTools scene explorer Ctrl+E or running scripts in the console F7, or specific mods.

ModTools scene explorer and console.

Scripts for commonly used prop shaders:

• Default
• Fence conforms to the ground. If you use the "high/low vegetation" props as the template when importing, the resulting props will have fence shader, but will also be height-adjustable using Move It!, which is unusual for props using the fence shader.
• Decal projects the texture onto the ground.

Comparison between Default (left), Fence (middle) and Decal (right) prop shaders.

You can add multiple prop assets to your prop as variations using a probability value. The probability is a percentage out of 100, but the main prop has no probability so it gets whatever is left over, so if you have two variations with a 25% probability each, the main prop will get a 50% probability. The variations will be embedded into the main prop, but also show up as separate props in the menu.

Run this script using the ModTools console F7 to set the variation amount, and also calculate equal probability automatically.

Prop variations menu in the asset editor.

The filename input is on the bottom left, this is what the actual file will be called. It's not recommended to use spaces, dots, or special symbols.

Save asset window.

Once the asset is saved, the .crp file will appear in the local assets folder:

%LocalAppData%\Colossal Order\Cities_Skylines\Addons\Assets

The AppData folder is hidden by default, you can access it by copying and pasting the path into the file explorer, or pressing Windows+R and typing in appdata.

CRP files in the local assets folder.

Once you have saved the asset and reloaded the game, you can publish the asset.

Go to the content manager > assets and find your asset, then click share.

Share button in content manager.

There is a folder icon again on the snapshot image, bottom right corner. Here you can change the Steam preview image, which is the thumbnail visible on steam. The largest size the image will be visible is 437x437 (on the front page) but it will get upscaled to 512x512 by Steam so that's the size you should use.

There is also the content folder, which is where the actual asset file is. You can paste multiple .crp files here if you would like to upload a pack of assets.

Publish window and content folder.

This is not something you can change.

It's the hidden internal name used to refer to your asset in savefiles.

It's the reason why a local asset is not the same as a workshop published asset.

For local assets: filename.Asset Name_Data
For published workshop assets: SteamID.Asset Name_Data

Comparison between local (top) and workshop published (bottom) prefab names shown in ModTools.