Despite there already being a thread on how to make a .tga tunnel many people are still unsure on how to make a .tga file, so I am going to make a proper tutorial on this. Also, this is a method that
Sheepocalypse uses and that he shared on Discord (not the whole thing), so thanks a lot to him!
How to make a .tga tunnelPreparation: Take a folder with a working .tga tunnel, copy and paste it, change the background.jpg and mask/tunnel.jpg to whatever you want
Step 1: Open paint.net (or pretty much any program that can make .tga files)
Step 2: Take a mask/tunnel.jpg that you want to use
Step 3: Choose the part where you want the spheres to go under it and color it white. Everything else should be black.
Step 4: Save it as mask_alpha.tga and most preferrably set it to a different location than the map folder that you are using
Step 5: Set the bit depth to Autodetect
Step 6: Open GIMP (you can also make .tga files by using Photoshop, but I don't know how to do it)
Step 7: Open the working tunnel that you have
Step 8: Open the .tga file that you made using paint.net as a new layer
Step 9: Merge the layers
Step 10: Export it as the .tga file in your map folder, causing it to overwrite. When a window pops up, don't change anything.
And that's about it! It should somewhat look like this.
If it still doesn't work, then
there's no help for you just wait until konisbored releases a video about how to make them, or it's the map.ui throwing a fit.
I spent a decent amount of time making this thread, hope you like it!