Here is a mini tutorial originally posted by Rick Hargraves at Elvastower.
Hi all,
When Open Rails build version 360 became available, I started to see 'bugs' just as the rest of you have so, I said to myself, "Myself, let's try to squash one", and that's what I set out to do. These experiments were conducted on the Xtracks narrow gauge track system.
The Bug: Floor height of 'buildings' to rail tops didn't match between the two sims in trying to hide the ballast. Sooooo, here's what I found out.
MSTS on the left, ORTS on the right.
Creating a single faced object and placing it over a flat straight piece of track on level ground then playing with the Y axis adjustment, I found that the rail tops between the two sims are a little off. (And I mean a very little.)
Notice the rail top's 'flicker effect' in the MSTS pic but clean in the ORTS pic, below. (Again, it's barely measurable.)
(I still use the Imperial system of measurement so all the following figures are in inches. You'll have to convert 'em yourself.) Now, from dead zero on the ground, (Y=0), upward, the tippy tops of the rails in MSTS are sitting right at .903 inches.Because ORTS' track sits a tad bit higher, the tippy top of it's ballast sits rightat .75 inches. (These figures may vary by about .005 inches, either way, btw.) My point is, to build a 'floor' of a model that you only want to see the rails on/in, its top surface/face must be between .75-.903 inches if you want the 'building' to work in both sims properly. And, here's what I did. The following pix show how I set the floor face at exactly .85 inches from ground zero to get this model into both sims properly.
Here goes... Same 'bug', floor height incompatible with ORTS
Notice the ballast showing through on this model in ORTS as well when set up for MSTS. What I did this time instead of raising the whole structure, was to just raise the floor face surface up on the Y axis the difference between its thickness and the .85 inches I found to work from my first example above, (Post #1). (Floor thickness = .333 inches. Difference I adjusted the face on the Y axis was .517 inches which totals the .85 inches I needed.)
And, the results are as follows; 
Now, it's time for the default MSTS trackage that most are still using. No need to go into a lot of details with this track. The rail tops from the ballast's top surface is a bit taller and so is the ballast. So, using a minimum of .9166 inches will give you a clear clean visual from a far away view. (Like high in the air.) Anything below the .9166 inch mark will cause a disappearing act of your building's surface face to show the ballast again. In conclusion, if you were to build a structure and wanted only the rails to show, start this structure off with a .85 inch thick 'slab' or foundation for the Xtracks Narrow Gauge rail system and a .9166 inch thick 'slab' or foundation for the default Standard Gauge rail system.(I found a good clearance at 1.0 feet or one foot for standard gauge, also. There is a bit more room to move on standard gauge track and I would recommend a one foot thick foundation for this gauge.) If you're only going to use a top surface face, make sure its Y axis is at .85 inches for Xtracks. Again, an even foot would be excellent. If you're only going to use a top surface face, make sure its Y axis is at .9166 inches for default track. I'm convinced, here's proof in the pudding. Building structures can be adapted for both MSTS and ORTS. (Let's document it and sweep this 'bug' under the carpet.)
Thanks, all,