Posted a suggestion to @jojos38 since he has some fine mods for BNG. Suggestion to get dirt and so on blended to cars can be seen here: https://beamng.com/threads/better-sounds-mod-4-4-work-with-0-11-0-5.38669/page-45#post-827542 The question though is if its possible to access and alter textures in Beamng, using lua. Can anyone here shed some light on this?
Technically you can alter the RGBA values of 'instance' materials (ie. the ones we use on vehicle's body, to allow the selector - those are special materials that should not be overused). So it would also be possible to control the alpha value of a texture as well (some plane mods uses that to blend in a 'blurred prop' texture AFAIK). Although the problem is not much the part where you change those values on runtime, but the layers available. You have 4 layers of textures available per material, which some vehicles uses all, others are around 3 layers. Each layer is an additional render pass, so using more equals to less graphical performance.
So basically one layer per effect (dirt, scratches..), which does require a layer to be available. Have i understood this right, that all layers are active from start and what you do to blend the purposed dirt layer is that you change the alpha value (which is possible to do on the go/while runnig Beamng)? --- Post updated ---