with custom thumbnails, you mean that the image that appears on the blueprint tab or in the workshop page? If it's the one on the blueprint tab, the blueprint is most likely broken (although i would need the link to check, since if you are careful it is possible to change that image without breaking it)

I was talking about the image that appears on the blueprint, i was also thinking that it was the blueprint being broken but i cannot load anything that has a custom thumbnail,
i was able to use one of them before but it no longer works

Originally posted by Weaponized Idiot:

I was talking about the image that appears on the blueprint, i was also thinking that it was the blueprint being broken but i cannot load anything that has a custom thumbnail,
i was able to use one of them before but it no longer works

could you send me the link of the blueprint?

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2697121971&searchtext=citi+car
Here, i made this one and it was working before i reopened the game later day, i also couldnt use a crane that i have downloaded from the most popular list (Also had custom thumbnail)

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2689089317&searchtext=Crane
And here is the crane im talking about

My creation might not be able to load, i dont know what kind of a system trailmakers uses for blueprints so i just overwrote the image in an editor

yeah, both of those blueprints are completely broken. They have none of the data the game actually loads, so no wonder the game isn't able to load anything. Furthermore they are missing the alpha channel, which the game expects blueprints to have. If it's not there, the game will completely refuse to even attempt to load the blueprint, because even if the data is still there the format will be wrong and the game won't be able to load it properly. Additionally, the crane doesn't even have the correct resolution, which also makes the game refuse to load it.

In general, unless you know extremely well what you are doing, attempting to modify the blueprint images will completely break them. The data the game loads is stored in the colors of completely transparent pixels, so any sort of image compression will get rid of it. Due to that, you need to make sure that whatever program you use to modify the image doesn't use any sort of compression when exporting them. Additionally, you need to make sure that you don't touch those pixels at all when modifying the image, which are the pixel at the top right corner of the image and at the bottom of the image (the size of this section depends on how much data needs to be stored. Usually it's a couple rows of pixels, but in some cases it can cover 25% or more of the image vertically). If you want to have a custom thumbnail on steam, there is a better method which don't rely on modifying the blueprints themselves (and thus won't be displayed on the blueprints tab, but will be on the workshop). This method is way easier than attempting to modify the blueprints directly and doesn't have any restrictions over the resolution of the image or what pixels you can modify

So its the blueprints that is broken, if overwriting it is most likely isnt going to work, how can i update it without risking loss of data, i tried searching for ways to replace the thumbnails and couldnt find anything for trailmakers

Originally posted by Weaponized Idiot:

So its the blueprints that is broken, if overwriting it is most likely isnt going to work, how can i update it without risking loss of data, i tried searching for ways to replace the thumbnails and couldnt find anything for trailmakers

the method is a bit comboluted, but once you do it for the first time it's fairly straightforward:

First create the thumbnail you want and a txt file, then rename that txt file to have a .vdf extension and open it with notepad. On that file write this (workshop id is the id of the blueprint you want to update, it's the number at the end of the workshop link after "?id="):
Then download steamcmd which is a command line version of the steam client made by valve from here and extract it into a folder. Go to that folder with cmd and run it (just type 'steamcmd' while on the same folder), this will update it and start it. After that type 'login username password steamGuardCode' (if you don't use steam guard 2FA you can skip that), this might log you out of the normal steam client. After that just type 'workshop_build_item "C:\\path\\to\\file.vdf"' which will update the workshop item according to the .vdf file (in this case it will just update the thumbnail as that's the only option present, there are a lot more things you can change with this method). Finally you can quit the program by typing 'quit'

Thanks for the help, one last question, how can i update the broken blueprint with the VDF?

Originally posted by Weaponized Idiot:

Thanks for the help, one last question, how can i update the broken blueprint with the VDF?

in game workshop->my uploads->select the creation->edit->edit blueprint->select working blueprint->upload. After that you can use the vdf file method to update the thumbnail

Thank you for your support