So you want to create your own assets… but you’ve found 3DSMax or Blender too challenging? This is the guide for you!

I have played Cities Skylines on and off since 2015 and have been interested in 3D modeling ever since I saw some of the great user creations in SimCity 4. I first attempted to create a model (plug for my Chick-Fil-A!) for Cities in 2015 using Blender, but found that extremely challenging to figure out. After some further research, I found SketchUp which was far easier and faster to create models, but then I didn’t know how to texture appropriately for the game. I read guide after guide that explained how to export a model from Sketchup so that it could then be textured in Blender. I’d get the model imported, then have the same frustrations trying to texture/UV Map. Eventually I gave up.

Fast forward 5 years…. Once the pandemic hit, I was bored and looking for something to do/teach myself so I started back in to 3D modeling and eventually after some trial and error stumbled into the SketchUp only asset creation strategy that will be described in this guide.

• Sketchup (I use SketchUp Pro 2017, but assume other versions will work)
  
• Sketchup Extensions
  
  • Cities Skylines Tools[extensions.sketchup.com]
    
  • SketchUV[extensions.sketchup.com]
• Photo Exiting Software such as GIMP or Photoshop (I use Photoshop)

Thats it!

Launch SketchUp and create your model!

I will not go into deep detail on how to create a model as there are plenty of guides online that describe this. SketchUp’s interface was so simple that I was able to create my first building without really needing any guidance. Be mindful and do not create extreme detail and tons of faces in your model as it causes performance problems with the game and because of this, people may not want to download your asset. Most asset creators provide triangle count and texture size info on their workshop assets (you should too!) so you can look around the workshop and get a feel for what is acceptable. The Mesh Info Mod by Boogieman Sam is your friend!

Be sure to use the guide grid from the Cities Skylines Tools SketchUp extension. This will add markers on the ground that will help with sizing your asset appropriately for the game. It draws a grid that reflects the 8x8 meter squares found in the game. I highly recommend looking up real world measurements for doors, garages, and the like as you develop so that your building is a realistic size.

Completed Basic Model!

Create your texture atlas!

In your photo editing software, create a 256x2048 pixel (or whatever Cities Skylines approved size you want) canvas. Always use multiples of 32 (64,128,256,512,1024) for the height and width or the game will not render correctly. Keep texture images as small as you can! I like to go with 256 px width and let SketchUp repeat the main texture like brick or roof as this allows you to get a higher resolution. You DO NOT (and depending on your model SHOULD NOT) have to do it exactly this way. It just depends what works for you and your model, this particular method works fine for smaller models. Asset creation will involve a lot of trial and error. Some people may design their atlas to be a 1024x1024 square and make separate faces in the model to repeat their texture, there are always many ways to achieve a good-looking final result. Don’t be afraid to use the Mod Tools mod to export other creators work to see how they textured and created their models. Don’t steal and re-upload their work though!

Find a seamless texture for your walls and roof and any other images you may need like doors, garages, windows, interiors, etc. and add them to your GIMP or Photoshop document.

Once complete, your image may look something like this and can be saved as a PNG.

There are many complexities to the texture maps that I will not get into (great info here and here[cslmodding.info]), but in the simplest form, what we are creating here is called the diffuse texture atlas and the PNG export of this should be placed in the

C:\Users\<youruser>\AppData\Local\Colossal Order\Cities_Skylines\Addons\Import

folder along with your eventual exported model. This texture will need to have the same name as the model with “_d” for diffuse. So, for example...

Model Name: House.fbx
Diffuse Texture Atlas: House_d.png

Make sure your colors are not too bright, the game overbrightens and oversaturates all colors.

Now, import your PNG texture atlas image to SketchUp using the material import button shown to the right.

You can then use the paint bucket to apply your texture. Click, resize and drag it around as desired! You can see below how the brick texture is repeated many times over the single face of the house.


Finish applying your texture atlas to every face in the model. You will receive an error upon export if all faces are not covered by the same material! Try to make bricks and shingles realistic sizes, this may require going back to your texture atlas, adjusting, then re-importing the image to SketchUp. It’s all part of the process.

Export your completed and textured model via the Cities Skylines Tools extension (button shown below)! If all faces do not have a texture applied, the export will not work.

Import your asset to the game! Check out this Asset Editor Guide[skylines.paradoxwikis.com] for more info.

Creating a custom LOD model via SketchUp is kind of a pain, but using the SketchUV extension it is a bit easier. I won’t act like I fully understand how this works, and if you are using this guide, you probably don’t care either! Cities Skylines requires that the LOD texture be between 0-1 on the Texture Map. In SketchUp, it means that with how the texture repeats over and over, it needs to be on a specific one of those repeating texture blocks. If it is not, you will see odd behavior in the actual game (not the asset editor). To address this, select the face you want to map -> click the SketchUV rainbow button, -> right click your model face -> choose box map. This will put the texture between 0-1 and from there you can resize however you need.


Don’t let the texture repeat on any faces of your LOD! For my LOD, I typically just choose a small size like 128x128 and add my roof texture as the largest portion of the image since that is what will be seen most from a distance. For bricks and other textures, I just grab my diffuse map from the regular and do a Filter -> Blur -> Average and use that color in the LOD texture atlas. You will never need to see individual bricks on a LOD.

That’s it! You hopefully now have a model in game.

Please provide feedback if you think any of this guide is too vague or hard to understand and I will do my best to improve it. I'll also try to answer any questions you may have.

Navigate here [drive.google.com]for all the source files that went in to making this house so you can review and hopefully make sense of it all. While I didn’t go into detail on this (review the other guides referenced above and below!), additional texture maps for illumination, normal, and specular are included. You'll be able to see how this is done by opening the Photoshop documents and reviewing the layers as well. It would have been so much easier to learn this had someone posted a full dump of all the files that go in to a simple asset so I hope this helps someone out there! Also, if you plan to upload your assets to the steam workshop please check out this link and the others below.

Happy modding!

*** This is not the only way or necessarily the best way to create assets for the game, it is A way that I found to have the least degree of difficulty to make nice looking assets that are also compliant with the confines of the game ***

Source Files from this guide!
Yinzerr House[drive.google.com]

Visit my Workshop Page!
Yinzerr's Assets

Asset Creation Links:
Normal Map Creator[cpetry.github.io]
Texturing and Asset Creation 101
Asset Editor Wiki[skylines.paradoxwikis.com]
Detailed Window Illumination
Cities Skylines Modding[cslmodding.info]

Steam Workshop Helpful Links:
Publish Multiple Assets
Publish Building with Included Prop as a Single Workshop Item
Basics of Asset Editor and Uploading