I made some small updates to the existing Diamond DA42-VI from the fgmembers repository.
Here is the download link: https://www.dropbox.com/s/kexmdyjlzhc7d2u/Diamond-Da42.zip?dl=0
And here are screenshots with the updated version: https://imgur.com/a/xD3HK
Updates description:
1) Current version has the performance too low compared to the new VI version (http://www.diamondaircraft.com/aircraft/da42/) so I made it go faster.
Unfortunately I don't know yet how to only increase the speed at high altitude so now it goes slightly faster than it should at low altitudes and slower than it should at high cruise altitude so somewhere in between it has the perfect speed
In the future I (or somebody else) might try to tweak it further for example by using a supercharged engine (my first attempts where not very successful).
These updates have no connection with my previous jsbsim model for the same plane from about 2 years ago which I have unfortunately lost.
2) Current version only had 50 gal of fuel capacity but the real plane can have a maximum capacity of 79.4 gal so I increased to about 80. The real plane can not use 3 gal but it also probably uses less fuel than the simulated yasim one (because it's diesel and yasim doesn't know that) so I hope it's close to reality (I didn't test the range yet).
Also current model used Avgas and I changed to Jet fuel since that is what this diesel model uses.
3) The real plane looks white and shiny but current liveries look slightly gray and a bit matte so I increased the contrast and saturation of the blue and red liveries and made a small change to how the engines look in the green one.
4) The most obvious update for which I have posted the screenshots is that I updated its looks by adding the new ALS effects (http://wiki.flightgear.org/ALS_technical_notes):
-New rain effect for the windshield visible from inside and outside. To tweak the rain drops flow use nasal\rain.nas and try new values.
-Inside shadows and irradiance on everything including all buttons, chairs, levers and human models. To implement this and other features I have changed many files, for every tiny button so someone should check if I didn't broke something.
-Shiny fuselage with reflections and rain effects. I am not completely happy with the new effect because the real model is white and shiny but this one is slightly metallic and shiny and I don't know how to make it white. The old version was white (and if your shaders for the model are at the minimum it will still be white) but it had no shine and no reflections.
-Reflections in the windshield for the inside and the outside. Since I am not good with 3d or 2d graphical editing I used the C172 cubemaps which is very close in size and window arrangement but someone who knows how to make new cubemaps for the shadow and the reflections should make them if they want.
-I changed the interior textures because in screenshots the interior seems to be covered usually in light brown leather or leather imitation so I tried to imitate that as best as I could while keeping the current 3d models because I don't know how to change them. Maybe changing the seats with others more similar to the real model would be good but I didn't found any. Also I tried to change the passengers (because they all look like clones) by using models from the generic folder but I don't know how, I only managed to transfer a head in one of my attempts
I am not using Rembrandt because it doesn't work with ALS and I have understood it's no longer maintained so I have no idea how my changes affected the Rembrandt version.
I have also contacted the original author, Helijah in case he (or who is responsible) wants to merge the changes in the main repository.
I might have made mistakes so I hope someone more knowledgeable than me can fix and improve it, for me this is the first time I make so many graphical changes to a plane and I mostly made them by reading other models and lots of trial and error.
I would have liked to add fog and ice because it's easy but I don't know how this happens in a real plane so I wouldn't know if I implemented correctly or not.
It's not very likely that I will make more changes (I might try some tweaks with the supercharger but I don't know if it will work) but if I do I will post here.
I hope other people will improve this model since it's my favorite general aviation plane