tutorial Sketchup to Cities: Skylines: The Easiest Way

[Elektrix 42]

Why You Shouldn't Use This Tutorial: A Preface [Important, please read!]
This tutorial does not necessarily create the highest-quality assets for the workshop. I'd encourage not publishing things made here. That being said, I still use this tutorial for things I use privately. Therefore, I have compiled a list of reasons when not to use this tutorial:

1. When you plan on releasing a finished asset to the workshop. This method creates unacceptable texture sizes; workshop assets with higher than 2k textures tend to use a ridiculous amount of ram.

2. When you have more than 15-20k vertices in your model. Frankly, you shouldn't be making any models with this many vertices unless you know what you're doing.

3. When you are making anything other than a building. This method just doesn't work with roads and never will. 

Please use Blender or 3DS Max, two mainstream modeling softwares, for any professional asset creation. You could even use Sketchup, but UV map in Blender or 3DS. It's not really as hard as it looks.

 

If you're still here, let's begin.

Prerequisites

• Sketchup 2018 or less
• Blender
• Cities: Skylines
• Texture Atlas for Blender. It comes default with Blender; it just needs to be turned on. See the link directly below this ↓ (at least on my computer screen) to learn how to install extensions.
• SCSH. <-- I made this. It's a Blender extension. Don't know how to install Blender extensions? Look no further than this StackOverflow answer 
• A model you made in Sketchup.

Quirks
You have to have every visible face textured or the face will be deleted by the script. Solid colors don't play nice with texture baking since they don't contain textures. This is subject to change in a future release so stay tuned. I too want to export solid faces.
Any face that you want to be visible must be front-facing (not dark greyish-blue with the default SketchUp material). It won't show up even if the backface texture somehow does miraculously get baked.

Smaller objects and buildings will look nicer than larger objects and buildings. That's what's going to happen for everything you make regardless of whether you make it in Sketchup or not.

I might have lied about it being four clicks to convert. It's more like seven to ten-ish. That's a lot more clicks, ohmygoshimgoingtodie

The Actual Tutorial

Step 1: Export your model from Sketchup. I'll be using the .dae format as I am poor and I can't afford Sketchup Pro. Make sure you triangulate all faces and export texture maps in the options menu. Do not use any other options as they can range from unnecessary to destructive. Edit: Make sure everything is exploded before you export. If you don't know what that means then you don't need to worry about it.

Step 2: Go to the Scene tab in the parameters menu on the far right. It looks like two primitives and a sun. Go to the bottom and hit "Blank Canvas". It's labelled with a big X. (Or you could hit A-A-X-D really fast, but this isn't a Blender tutorial. Do whatever is comfortable for you.) Import your .dae and hit "Quick Convert" in the panel on the right. It has a star next to it, you can't miss it. Make coffee or do something else while my plugin:

1. creates a big texture atlas using the texture atlas plugin (less than 1 second)
2. uv unwraps your model into the atlas using blender's builtin uv unwrapping algorithm (less than 3 seconds)
3. marks the initial uv map of each mesh as renderable while selecting the new map for the upcoming texture bake (less than 10 seconds)
4. bakes the texture to a 16384x16384 image for maximum resolution (feels like actually forever and felt even longer in testing, but it's only about 3-5 minutes for most)
5. joins all the meshes together (less than 1 second)

Step 3: Once the process finishes (again, it will take some time so don't freak out), export your model as a .dae. Make sure your Texture Mode is set to "UV Textures".

Step 4: You should be now left with an Import directory with your model and a near-200MB texture named TextureAtlas.png. Now for the love of all that is holy in the world open that bloated texture up in your favorite image manipulation program and scale it down to an acceptable resolution. 2048x2048 (2K) is pretty much going to be acceptable in most cases. The largest size you should try to get away with is about 1MB. Rename the texture to [whatever you named your sketchup model]_d.png and you're done. Import it to C:SL just like any other model, and make sure to scale it up by 2.54.

Eh, I've made better. There are a few underlying issues with this model (incorrectly oriented faces causing incorrect textures to be displayed on the stairs and metro sign, MoM trench tracks not working how I thought they did, etc, but this model serves its purpose as a demonstration.

Why don't I just render to 4096x4096 in the first place to skip the fourth step? I tested it and I felt that while it took significantly longer to render in 16384x16384, I tended to get better results if I rendered to the full resolution and scaled down later. If someone wants to give a technical explanation I'm all ears. At this point, I assume that Blender's raytracing algorithm will create less detailed results to begin with than the downscaling method used in GIMP or Photoshop. If you would rather use an initial texture size of 4096x4096 and skip this step, use Manual mode (sequentially click each button, and between "Create Atlas; Add All" and "Auto Unwrap to Atlas" go down to the Render tab and scroll to the bottom and change the resolution to whatever you want. Eventually that will be a GUI in my extension; I'm just too lazy to make it right now.

How can this method be improved?
There are a few things that I'd like to change in the future of the Blender extension especially. In the future, I'd like to be able to bake solid colored faces but that would require a rewrite of a significant portion of the script.

I want to be able to generate LODs. At this point, you have to simply repeat the process with a LOD model entirely. Since this is exactly what you have to do when you make 3D models in any other modeling software, I'm more or less fine with the work. I do find that the game-generated LODs are more or less fine for my city, which is why I typically don't make them for personal models like the metro station viewable above.

It would be really cool if I could make this into a Sketchup extension. However, learning the ins and outs of texture baking and atlas creation was not really on my list of todos for this semester, especially since I already have college classes to think about and other C:SL-related projects to tackle. I still plan to finish my script that unsubscribes from unused assets and make it understand packs. I still plan to do some simple modding eventually.

I'd also love to implement a better UV unwrapping algorithm, as the most important thing here is that the materials are preserved with their correct scaling and not that each face gets its own distinct texture. This would allow for much smaller resolution textures (smaller file sizes) without decreasing texture fidelity. Or, on the other side, similar resolution textures with heightened texture fidelity.

Q&A
Q: Can I use models from the Sketchup 3D Warehouse?
A: For personal use (not for publishing to the steam workshop), always yes. If you plan to publish the asset to the Steam Workshop, please get the permission of the original author first.

Q: I'm getting weird black lines on the model in Cities: Skylines.
A: The best way I've personally found to get rid of the black lines is to manually subdivide large faces in Sketchup. That way the face can be broken up into different areas of the UV map when the model is imported to Blender.

Or you could open up the diffuse texture in your favorite image manipulation program, select by color (choosing black) and delete those pixels, causing transparent areas where the black areas used to be. Then duplicate the layer, select the one underneath the texture, and blur it. This works... sometimes. It should look like this:

Q: How do I get textures for solid faces?
A: You can use "unique textures" in Sketchup, or you could search online for a solid color texture and make a new texture. This, again, is a limitation that I hope to remove in the future.

Q: I don't have my texture in the Import folder after I export?
A: Look at the GIF in Step 3 and make sure you're exporting as a .dae.

Q: My texture won't load in the game?
A: Your texture is most likely not named correctly. Make sure it is marked as a diffuse map for that model by giving it the same name as the model with the suffix _d. It may also be too big. 200 MB is completely unacceptable as a texture size unless you're making something absolutely massive. It may also not be in a power of 2. Acceptable texture dimensions are mixed-and-matched from this list: 256, 512, 1024, 2048, 4096.

Q: My model is way too big in tris but it shouldn't be?
A: Go into Edit Mode in Blender, select the entire model, and hit Remove Doubles. You can search for it in the Space menu if you don't know where to find the button. If your faces are incorreclty oriented in Sketchup you'll end up with a garbled mess which is why I didn't automate that portion.

Q: How can I manually UV map since 4K res is too big?
A: Use manual mode (sequentially click the bottom buttons) and skip "Auto Unwrap to Atlas" and instead substitute manual UV mapping (if you so chose to torture yourself like that). It's not fun to manually unwrap Sketchup models in Blender, so you're kinda better off starting off in Blender to begin with and modeling the whole thing there.

Q: My textures are still low res?
A: You'll definitely not want super long faces. That doesn't play well with Blender's UV unwrapping algorithm (for obvious reasons?). Manually subdivide those faces in Sketchup or manually UV map in Blender. If you have an absolutely MASSIVE model then you might not want 4K textures, but to be quite honest that's all you really should be using, so...

All right, hopefully that covers everything. This is my first time making my own post on Simtropolis instead of commenting on someone else's, so I hope everything here is correctly formatted and factual. Also, hopefully this tutorial will help people other than just me  

If you have any questions or tips or comments I'm all ears. I consider myself to be ridiculously lazy so it is in my best interest to implement anything possible to save myself and other people time and most importantly effort.

[boformer 3,169]

Excellent tutorial. That looks very helpful. If I ever get back to modelling, this will be the way to go.

@Avanya please pin.

[Ronyx69 2,413]

On 12/1/2018 at 5:30 PM, Elektrix said:

Now for the love of all that is holy in the world open that bloated texture up in your favorite image manipulation program and scale it down to an acceptable resolution. 4096x4096 is pretty much acceptable in most cases. The largest size you should try to get away with is about 6MB, in my humble opinion

Are you seriously trying to say 4k is an acceptable resolution? Especially for that concrete box of a station?

4k is insanity and should only be used for huge insanely detailed buildings, the largest texture I've ever used is 4096x2048 for one of the crazy big sedona cliffs, and that's a very special case.

Normally for buildings i've used 2048x1024 a couple times I think, mostly it's 1024x1024 or 1024x512.

I don't use sketchup or blender so the rest of the tutorial might be good, but I can't believe this got pinned to the top, it will definitely give many people the wrong idea and create an influx of terribly optimized assets.

[boformer 3,169]

1 hour ago, Ronyx69 said:

Are you seriously trying to say 4k is an acceptable resolution? Especially for that concrete box of a station?

Calm down. I agree with you that a 4k texture is too big. 1k is more than enough for average buildings, and the LOD texture should be really small (256 or 128).

I think this is still a great tutorial and workflow, especially with the texture baking.

[Elektrix 42]

I completely agree with you, 4K is entirely unacceptable for well-mapped assets and suggests that your model needs to be better optimized. Since writing that part of the tutorial, I've changed the method in which I scale down textures and after having recently tested it again I can confirm that the difference between 4K and 2K is negligible and frankly unnecessary for most models. I will be updating the tutorial accordingly.

The reason why I used 4K to begin with was because at the time of writing that part (back in November), I was using a very bad downscaling algorithm and/or was baking the textures directly to 2K (producing worse results). I updated part of it when I started baking to 16K and scaling down, but forgot to update the final res, I suppose. Blender's UV map generation doesn't produce well-optimized maps, so I can say with definite certainty that 99% of the time going under 2048x1024 is going to look ugly for most buildings unless you're UV mapping by hand (which is possible but not recommended for Sketchup).

It's also fair to note that if optimization is what you're going for, it's a lot better to do things traditionally and by hand. I wouldn't recommend Sketchup for anything other than creating scale buildings or whatever happens to be in your imagination. It's versatile and easy to use, but it's certainly not an industry-grade 3D modeling application. If you're doing anything else (road modding, tree making, etc) it's better to use Blender or 3DS Max. This tutorial is called "the easiest way" for a reason, and me writing it was much less "let's ruin the C:SL workshop by introducing bloated and awful assets stolen from the 3D Warehouse" and much more "wow, I finally finished a way for people not skilled at 3d modeling or texturing to make what they want for C:SL". I hope that this will promote the second, and not the first.

[i509VCB 2]

Of course I had to spend an hour to model up something to test with. And it works. No awkward output, texture applies with no issues. Larger object I modeled doesn't have any texture artifacts that I can see. Textures did not misalign in the process either, so very precisely textured buildings will export as they look.

The only issue I had (probably with blender and not the tool) was the textures not showing up in blender preview. Though the textures export basically the way they appear in Sketchup.

This tool will not create Alpha, Color, Illumination, Normal and Specular maps, so do not expect your buildings to light up at night, or have clear glass. Though I did expect that coming into this as that is more advanced asset creation. (Of course I am still trying to learn how to create these maps)

Once you learn how to make the other texture maps, you could model about anything and plop it into Cities skylines with no issues.

Even if only 50 people use this tool ever, there will be some great buildings that come from it. After a bit of time.

Well time to start making more of those airport assets. 

[Darf 1,439]

Well, this is by no means the easiest way (though it is a way). SketchUp plays a lot nicer with 3dsMax. There's no export process and import just imports all assets with applied textures, ready for baking. No plugins needed. I also agree with Ronyx that this is not the way you want to learn new users to start creating assets. Sketchup is one of the worst programs to texture. It has a very nice poly editor that's good for architecture, but that's about it.

[Elektrix 42]

Unless this has changed since the last time I researched it, 3ds Max is not free for non-students or educators, which is why I don't really consider it a long-term viable solution even though it is certainly a valid way to port assets and its UV unwrapping algorithm is far better than that of Blender. I will most certainly not be paying upwards of $200/month for it after I get my degree as that's not really a price that I can afford in the foreseeable future and I suspect that unless it's a major priority many others won't be subscribing to it either if they're on a tight budget. That's why I used Blender here— not only is it easier to automate with short Python scripts (bringing users nearer to a one-click solution), but it is also free for everyone. The application itself is also much smaller (I believe it's a difference of several GB last update of 3ds Max?) and for users with limited file space, it's also important to budget that. However, I may be wrong; I haven't used 3ds Max in quite some time, having preferred Blender immensely for versatility and extendability (and load time on my computer ).

I respectfully disagree; forcing users to believe that for some reason or another Blender/3ds Max and an ultimate standard of perfection are necessary for any "legitimate" asset creation is not only discouraging, but has, I personally believe, created the large divide in quality that is evident on the Steam workshop, so I feel that the current method isn't necessarily the right way to start either. This high quality abundant throughout the community is preferable, yes; but it's not necessarily easy for new creators without much/any knowledge of 3D modelling+texturing to be acclimated to the community. Not that I have ever been disappointed by the incredible quality of the workshop, or that I think there are no newcomers to the community whatsoever who are skilled at modeling and texturing, or that I think newcomers should be pandered to, or that I think publishing this tutorial will solve the issue, or that I think learning Blender or a related tool is that hard. I just think it's an entirely artificial divide that is unnecessary in a game modding community. For job applications and work, sure, but this is a community for hobbyists modding an individual game that we play for fun. If someone publishes an item to the workshop that any individual feels is not to their standard of quality, I see no reason why they can't simply dislike the asset or not subscribe to/follow the person. I don't wish to cause any animosity or argument, and I don't wish to sound arrogant or demeaning in any way; I just would like to explain my position here. 

Would you like me to update the tutorial with a disclaimer as to what cannot and should not be made in Sketchup? That may offer a solution that everyone is fine with.

@i509VCB: I currently create illumination and specular maps by setting all windows to an absolutely ridiculously colored texture (like hot pink or in the below gif light blue) that is close to a solid color that I can easily spot in generated maps. Since the faces with said texture stand out so well, I can either manually select them or select by color and fill those areas with white (window). That will make a specular map for many purposes. The texture will be overridden by the window texture anyway. Then it's just a matter of filling each window with greyscale colors for the illumination map or creating a textured illumination map if you know your textured map well. 


Generating normal maps, specular maps, or illumination maps using baking requires a bit more knowledge of Blender than I assume potential users of the plugin have. Textures in Sketchup only have diffuse components so you would need to generate each other component manually or using image editing and then apply them to each respective material. Not that it's impossible to automate in some circumstances, but I didn't really think it was necessary or viable.

Edit: The reason why you were unable to see the textures in the Blender window is because you were very likely still in Material display mode. Change this option at the bottom of the 3D view:
 

[Darf 1,439]

Well, that's certainly an argument you can make for using blender and your tool will certainly help with that. The student version technically is limited to 3 years, but not enforced (atleast I think). Sketchup won't be free much longer except for the web version either. My argument for using 3ds is that it converts very nicely. Not only does 3ds import textures, but also components and other geometry and hierarchy.

I certainly would not recommend people baking textures, if you don't know what you are doing. UV unwrapping by hand is usually better. While your tool and guide are not made for it, it will certainly give people an easy way to download 3d models from the 3d warehouse and convert to ingame models (and publish to the workshop). These models don't look good on a 2048x2048 texture and are quite big usually. Not only do you use somebody elses work, but it's very bad for performance aswell. I'd argue that some effort required in that case is a good thing. I certainly don't hold it against people that are new to modeling to post unoptimized models, but that blatant copying from warehouse I'd rather see go away.

[i509VCB 2]

I've played around with the tool a little more and asked some questions elsewhere.

Are you considering on adding an aspect ratio choice (Such as 16384x8192 as an export for the Texture Atlas) or is this something you have tried already. One other person I talked to mentioned something about UV Stacking which should allow the texture size to be smaller.

[Elektrix 42]

I will repeat:

On 12/2/2018 at 2:36 PM, Elektrix said:

This tutorial is called "the easiest way" for a reason, and me writing it was much less "let's ruin the C:SL workshop by introducing bloated and awful assets stolen from the 3D Warehouse" and much more "wow, I finally finished a way for people not skilled at 3d modeling or texturing to make what they want for C:SL". I hope that this will promote the second, and not the first.

 

@i509VCB Sorry, I had finals and other personal obligations that caused me not to be able to respond in a timely manner, so I apologize if you're still confused. You can already do this using manual mode. Hit the first two buttons in manual mode, then go to the Render tab (has a camera on it), scroll to the bottom, and change xRes and yRes (which should be 16384 and 16384) to whatever resolution you want before you bake. Then you can go through the rest of the Manual buttons sequentially or do the process manually from there.

As for automatic UV stacking, that would require me to write my own UV unwrapping algorithm which I would rather not have to bother with as Blender's algorithm is already quite complicated as it is. However, I will do some cursory research on UV automation for Blender and if it's possible I might make a project on it. Heck, I'm on break, I really don't have much better things to do anyway.

 

One thing that I will most certainly be implementing in the near future is an automatic mesh splitter by texture. Basically, if a material that was applied in Sketchup has suffix _rotors then unwrapping and baking will be applied separately and all rotors sections will become their own mesh so that a submesh can be created so that we can get working windows. That's a longwinded way of saying that I'm attempting to add rotors and additive shader support in a straightforward manner. I should have a POC up hopefully at the end of the day. Maybe.

[Mr_Maison 2,426]

Thanks for this method. I usually export from Sketchup to Blender to UV map and export. The reason I export from Blender is because Sketchup files tend to be bigger. I tried the plugin by ThomThom that exports right out of Sketchup and discovered the exact same model had a larger tri count than exporting from Blender. (perhaps it have something to do with the fact I exported as OBJ?) Did you test the tri count differences from one format to another? The one thing that have me intrigued about this method is the texture baking. If I can just use Sketchup like I do when making architectural rendering and not worry about using only one map, this will change how I make buildings for the game. My only concern is texture quality, that's why I never used baking before. But I see you address that concern.

[Elektrix 42]

The reason why exporting straight from Blender tends to have less tris is because Sketchup tends to create duplicate vertices when exporting .dae or .obj models (for unknown reasons, but I think it's likely because of the way texturing works internally). If I remember correctly, all you have to do to get the tris down after exporting is just to hit Remove Doubles in edit mode after you've re-mapped the shape, although that process may need to occur slightly sooner in the process as I haven't done it in a while. From one format to another I believe the difference is negligible and would be resolved with Remove Doubles anyway. I use .dae here because it's in the free version of Sketchup, but the process could be used with .obj or .fbx exports as well.

As for texturing, I've found that if models I make in Blender that I UV map manually tend to look best and are optimized well at 2ⁿx2^m pixels, then typically a Sketchup version created with my plugin looks best and is best optimized at 2ⁿ⁺²x2^m+2 pixels, and the larger texture size is typically passable, in terms of RAM consumption. I rarely have textures (2K or 4K for personal use) that are much greater in size than maybe 2 MB. But ultimately, the objectively best texturing work and UV mapping (at least at this stage of the tools available to us) is done by hand.

Sorry for the hurried response, I'm between classes currently  

[RaeFromStateFarm 3]

I get an error whenever i quick convert

[Elektrix 42]

6 hours ago, RaeFromStateFarm said:

I get an error whenever i quick convert

enable texture atlas plugin.

[RaeFromStateFarm 3]

1 hour ago, Elektrix said:

enable texture atlas plugin.

Now that i've done that this happens  

 

[Elektrix 42]

you have too many polygons, the tool is overloaded and will produce bad results. use a planar decimate modifier until you're well under 20k tris.

[kinnemf 0]

I installed the plug in and the box is checked but the tool either isn't showing up or I can't find it. 

[Elektrix 42]

it's likely that you didn't save user settings. you probably just can't find the tool, it's under the scene tab in blender 2.79.

going to be updating this tutorial severely.

[RaeFromStateFarm 3]

On 3/14/2019 at 9:00 PM, Elektrix said:

you have too many polygons, the tool is overloaded and will produce bad results. use a planar decimate modifier until you're well under 20k tris.

Still happens after i reduced it to less than 10k tris

[Elektrix 42]

don't rename your sketchup model

[matthiasbasler 2]

Hi Elektrix, just stumbled about your thread and your Blender extension after getting a headache baking my texture manually and re-texturing my SU model with it (which stems from the Google Earth modeling times). This seems like a huge time saver for me.

Anyway, it is a relatively simple model - a hundred faces before export  (360 triangulated). I tried to follow your tutorial closely, exploded components and triangulated during export. I used the older SketchUp Pro 8 and tried both .dae and .obj export.

I can do all the "manual" steps in your list up to "Batch Mark Correct UVs ..." where I get the attached error:

Seems somewhat similar to the one posted by "RaeFromStateFarm". I use version 0.5.0 of your Blender extension in Blender 2.79.
Can someone please give me a hint what could be wrong? Could it be there's some solid colored face left in the model?

Matthias.

[The Legendary Frank King 0]

Thanks for this tutorial.  I keep getting a similar error to the one listed above when you said there were too many Polys. Even when my model has less than 10K Polys.

I only got the quick convert to work once.  This error appears on the last step when I go through the script step by step.  I've done a decimate on a lot of files and I'm getting this error even on files with less than 6K Polys.  Any help would be greatly appreciated.  Thanks

 

[hvdnghia 0]

Photo to City skyline ? SIR ?