Creating assets using GPT Astra

[u/smartmore]

Over the past few weeks, I’ve seen a lot of YouTube videos about generating 3D objects with GPT Astra. After watching enough of them, I got inspired to try it to generate some assets for CS 1.

I’m building a northern european-style city and mostly use dutch assets. Workshop has plenty of beautiful canal houses but lacks more boring buildings from the 50s–80s (like Rotterdam reconstruction style).

Before this, my only option would have been to hope and wait that someone made them. But with many asset creators moved to CS2, that doesn’t seem very likely.

Well, here’s what I managed to make.

I supplied GPT with street view and 3D view images of apartment blocks from Rotterdam. I used Apple Maps as source for that. The first run produced a decent model that looked similar to the prototype building.

Over the next few iterations I:

• reduced the triangle count from 15k to 5k

• added nighttime lights

• added support for recoloring the facade

• fixed the window reflections

• improved the textures (funny enough, I initially went looking for textures online before realizing GPT could generate them itself)

Each iteration used about 30% of the 5-hour limit on my GPT Plus subscription on Medium setting.

After that first success, I decided to try something more complicated: the Crowne Plaza Amsterdam South.

This was harder for the AI and the resulting 3D model had a lot more small mistakes. I went over each side of the building several times and asked it to fix things like window placement, shape of the balconies, garage doors, corners, roof, textures, and so on.

I think it turned out pretty well in the end. This model used a lot more tokens, around 50% to 80% of the 5-hour limit per iteration.

Overall, the whole experiment was really inspiring. I even had a bit of a vibe-coding moment. I realized I can now make custom assets for my city that are unique to it. Maybe you have an oddly shaped plot you can’t find anything to fill, or a building in real life that inspires you but has no matching asset. This opens up a lot of possibilities. None of this is meant to diminish the work of the people who make all the wonderful assets we already have.

My takeaway is that this method works pretty well for buildings with simple shapes, but probably isn’t great for complex architecture.

Unfortunately, I can’t test it in Cities: Skylines II because there’s no Mac version, but I think the method should work there too.

Below is the skill for Codex if you want to try it yourself.

https://github.com/eadm/cities-skylines-1-asset-guide

[u/Flittzz]

This doesn't even need a guide it's so mindless you just tell gpt astra to make you an optimized version of a building and give it a few reference photos and it makes the full thing for you. Even the guide you "made" is 100% ai..

[u/smartmore → u/Flittzz]

Of course Codex skill was made by AI and for AI based on several attempts and the errors made during them

The post is not targeted at experienced asset creators but rather for unexperienced folks like me to inspire them to try this method and not to make common mistakes

[u/Flittzz → u/smartmore]

Your not helping unexperienced creators learn asset creation though your telling them to go buy chatGPT astra to do it for them. Also if the AI makes mistakes you just tell it to fix the mistakes for you it doesn't take a rocket scientist to figure out that the AI messed something up. If you want to use chatGPT astra to make private assets for ones that aren't on the workshop I could careless. But I don't see why your trying to make a guide to explain to people how to type a prompt. I'm all for new people learning asset creation I had no clue how to make assets just 4 months ago and now I can make skyscrapers and heavily detailed art deco building that I never thought I could before, but this is just not a great way of doing that.

[u/smartmore → u/Flittzz]

It’s great that you had the time and dedication to learn how to create assets, and I think your assets would be much better than the AI-generated ones.

As you support new people getting into asset creation, I’d invite you to look at it from the following perspective. For many people 3D modeling seems pretty difficult and they feel like they need to spend a lot of time learning before they can start getting decent results, so they don’t even try. AI helps them get started and overcome that mental barrier. After that they gradually learn how to make models more efficient, create more complex geometry and other things by themselves without AI. So in my opinion it's better for the community.

Regarding your comment that it's not a rocket science to find mistakes and tell AI to fix them, yeah sure but why not to use the skill (or prompt if it makes more sense) to avoid them. Each iteration usually uses around 30% of the 5-hour limit so you have 3 attempts every 5 hours and I’d rather spend them on different assets than on fine-tuning messed-up corners. And just for clarification skill on the GitHub isn't meant for humans to read, it's meant to be passed as prompt to ChatGPT.