Long story made short: Yallis posted on MM2C his reverse-engineering of the MM3 cars format, I wanted to go further: I begun reverse-engineering also the cities and making (or at least try to) a porting of MM3 to PC using the Unity engine. I have not made much so far, and I don't know if I will ever finish it, but here is a preliminary build. It features some menus, the vehicle selection screen, and a city viewing mode. Also here is the Unity project with (only) the source code.
UPDATE August 10, 2015: I made some fixes to the city loader (missing and messed up buildings are now fixed, and roads are placed properly) and added a simple loading screen at city loading.
Build 2 (Requires "Data" folder from Build 1)
Unity project code
UPDATE August 14, 2015: Implementing proper vehicle physics is not a walk in the park, especially with the new wheel collider in Unity 5. On Unity's asset store there is an excellent vehicle physics system, (here is a demo) but it costs 60 USD, and I don't feel like spending this sum of money on something I don't know if I will ever finish. If enough people are willing to donate something, I will buy the asset so I will be able to make in a reasonably short time at least a demo in which you can drive the cars in the cities.
Donation link removed on July 23, 2017
UPDATE August 14, 2015: carking1996 was so generous to provide himself all the 60 USD, I can proceed with adding driveable cars. Anyway, further donations are welcome if anyone wants to donate. (side note: I didn't check how much Unity effectively charged, it didn't show VAT, so it cost effectively 65.39 EUR = 72.92 USD, the difference of 11.79 EUR is not much, and I paid it)
UPDATE August 15, 2015: I just made a build in which you can drive cars. Cars are still in a very preliminary stage (no sound yet, as I have to decode the MM3 cars' sound script file, and the handling is not yet the same as the original MM3 one, also there are some shader bugs). You can download the build here. (Requires "Data" folder from Build 1)
UPDATE August 15, 2015: My box.com account has reached the 10GB monthly bandwith limit, so the box.com links don't work now. I reuploaded here the Build 3, and here the Data folder.
UPDATE August 30, 2015: Build 4 is available, you can download it here. (it requires the Data folder from Build 1) Here's the changelog:
- Loading screen modified, now it's rendered with proper size and aspect ratio (the selected car's loading screen now is also used)
The car color/skin selected in the menu now is also loaded ingame
Car tuning and stability improved - now cars behave much more like in the original MM3 (even if still not in the same way)
Added a small temporary km/h speedometer in the upper left corner of the screen
Car cameras fixed
Ingame camera FOV changed from 60