I was playing around and fixing stuff in existing bullet projectile function and this is what i've got
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Looks pretty ok, will need some more tweaking but atm it was fastest solution that actually worked very nicely.
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How to?
1. I used a texture of a bullet for a projectile, fired it normally as i did before.
2. Used a second texture that fires and has range up to 8 meters infront of marine and imitates smoke, or a bullet trail, it also grows so it feels like the smoke is dissipating as well as going transparent.
Pretty happy with the result, improvement to this would be writting a shaders that dissipates smoke really well, but that's out of my league xD