• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

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P3D v4 SDK V-4.5 MDL Modifier idea. Throwing this out there.

Hey all,

We get these really nice, updated SDK's for Max for compiling models for Prepar3D. But lots of people still use FSX, so we have to bounce between the newest SDK and the old 1.4 SDK so that we can also make a model that works in V1 and also in FSX. (A lot of people still in V1 per old computers and vintage DirectX). With that, we are really still stuck with using the FSX / V1.4 version SDK if building models for both FSX and V4.5. No matter what, we have to create a version of model that works in the oldest version SDK, which means we have to make alternate Materials for things that go over the 64K poly limit, etc, etc, etc. Also V3 had new materials which crash the V1 system (and FSX) so we couldnt use that either. Only SDK V1.4 works with FSX. So we might as well build models in that mode instead of the cool new V4.5 SDK.

But... What if we had a program that could 'scrub' and modify a V4.5 MDL file and convert it to V1.4/FSX? Not a recompiler. Only something that would change label types of Materials inside the MDL file. All the rest would be unchanged, (if that can be done).

I was toying with the idea of possibly hand editing a model file to see if it could be done.

I know MCX can reconvert a model from 4.5 to FSX, but it re-runs it through the FSX level SDK. Any materials that have maxed out polygon numbers will have to be redone as it crashes the compiler. Also, for some reason, the compiler system in MCX will have errors in the MouseRects for some reason. The system that MCX uses still re-uses the old system. It doesnt do a scrub and re-write, modification process.

Just wanted to throw that out there... See what you all think.

I am so tired of redoing planes with the antique V1.4 compiler.... Surely there is another way. Surely a V4.5 can be adapted by a form of editing to work in FSX/V1.4.


One solution is to stop FSX development. With MSFS2020, I think that FSX will not continue to be used .... or as FS2004 with FSX.
A lot of people will change to adop FS20, P3D or X-Plane, in my own opinion :confused:


Resource contributor
I think you’re stuck with building for both sdks for the moment, unless you can afford to drop FSX development. Only you know the numbers there, and I’m not going to ask. I do think when 2020 launches there should be a move to that which sinks FSX pretty quickly, but patience, mon brave!


Resource contributor
Things are much as they are in Bonnie Scotland - toilet paper is scarce, soap and hand sanitiser likewise. I had no idea people ate so much of the stuff. Schools are closing for the foreseeable tomorrow, all leisure facilities too, so the taxi bill for running the family to their after-school activities will disappear, and the roads were noticeably quieter yesterday because people are working from home where possible. Just like Phoenix, AZ!

At work, each company vehicle has a supply of hand sanitiser because we work in people’s homes a lot. One of the boss’s good ideas! Yesterday I was on an island where toilet paper was still available, so I bought a ginormous pack of 9 rolls.:rotfl:

Now wash your hands again!! And take care of yourself, Bill!
lolol... Roger that. I was blessed with a 9 pack the other day at WallyWorld.

I didnt know you were in Scooot-lahnd! Nice... Do they make you all wear nice plaid dresses over there still? Or was that a thing of the past..? We havent gone through the dresses stage yet.

We had some intense rain. Its becoming like the Highlands... All green. No more beige dust. A blessing, as I think it cleanses the air, keeps the airborn plague from doing its damage. Today though is clear.

Stay safe. Lets all get through this safely. Enjoy the 2 week home vacation if at home...


Resource contributor
Much as some politicians would like to make us dress, speak and act in certain fashions, we gentle Scots smile quietly at such prescriptions, make rude gestures and sink the heid in them. Then we vote the scallywags oot! So should you visit this fabled land, you will find place names in Gaelic where none was spoken in 200 years (and gey few speak it yet) and the Police are also the Poileas (according to their patrol cars.) I got married in a kilt and hivna worn yin since, being a most impractical garment in my line of work. Of course there are Gaelic-speaking areas where life proceeds at a lesser pace; there's no hurry at aal, at aal, och no; not like these hasty Spaniards with their manãna. But even there you will search high and low for kilt wearers except at social functions.

If you welcome rain, we can ship lots more your way; we have plenty to spare!

I was able to save it in TXT and then back into MDL format.

All materials that it uses are in there in English. But thats about it. No mention of how the materials are linked to parts, etc. Nothing about material settings and things.

Animations appear at the end.

I had heard that it was Materials that were the primary cause of crashing MDL files. If.... one could re-write (edit) the Materials of a P3D V4.5 to be V1.4 format, it 'should' work...

Materials in Viking.JPG

This is near the top/front of the file, showing materials it uses. I have a massive amount of them in this plane. :S

Below is machine code of the model. I can only guess its vertices and bits. Mappings...



This is near the back of the MDL file (bottom and end zone).

The idea reminds me of back in the FS2004 days, hand editing files to compile HUGE MDL files. I was up to half million poly's in a 65K limit FS9 MDL, lolol... Wild times. We would splice several models together into one massive model.


Staff member
FSDevConf team
Resource contributor
Hi Bill,

It's not that simple. The binary format of how materials and polygon indices are saved is different. So you can't just copy paste some bits around. That would also break the length fields that are in the mdl file and make them corrupt.

A tool like MCX is your best approach. It should split up parts that have too many polygons automatically.

The mouserect things sounds like a bug to be looked at.
Hey Arno,

Roger that. Thanks for the input.

I was actually working with MCX today, coincidentally. I was converting the models from V4.5 to FSX, but for some reason, they are invisible in FSX. They compiled fine, which blew me away. Usually it takes 1 to several days of getting parts divided into new materials so they will compile through the V1.4 compiler. But this time, they just went through. Slightly smaller file sizes.

I tried the models in FSX Steam first, didnt work. (They just had a 1.8 gig update). So I tried FSX standard, and they were invisible in there also. Before posting this, I reexported again, tried them again, still invisible, and also tested the planes in P3D V4 and they show up fine. So some little something is causing them to not show in FSX but otherwise they are good models.

AND>......... The mouserects were all good! Nice fix. I was working on models with the last version MCX, not this newest one.
I checked the max texture limit's in both FSX versions. One was 1024, changed to 4096. Other was already 4096. Retested, nothing. No joy.