I've been meaning for weeks now to write up some notes about 10.40. I've also been trying to put the hood back on 10.40 so we can get it to public beta; instead the last few weeks have been a flying circus of driver bugs, expiring certificates, etc.
But we are making progress, so I'll start off in this post by describing a change in how DSFs are loaded and the wide DSF box.
A Tangent: Stuttering and Pauses
A post that involves X-Plane pausing during flight is going to invariably bring up a bunch of blog comments: "X-Plane stutters while I fly on my really expensive machine!" This is not good, and from what I've been hearing, it sounds like something got worse recently; this is something that we are investigating now.
But I also want to mention that historically, X-Plane has never been "no-pause". What we have done is periodically made the pauses much shorter; our goal is to get down to zero pauses, ever, but this will happen by finding every source of pausing and fixing them one at a time. In other words, we're in the middle of a process of improving smoothness, but even if one source of pausing is fixed, another source might still be causing problems.
DSF Loading: the Old Way
X-Plane has, since X-Plane 9, loaded DSFs in the background on a second core while you fly. This cuts down the amount of time it takes to change scenery. (Older versions of X-Plane would pause while scenery was loaded and shifted.)
The old DSF loader did have a few weaknesses though:
- The sim pauses while DSFs are deleted. As DSFs become bigger, this pause is becoming more noticeable.
- If the loader ever gets behind by two scenery shifts, it just waits until it catches up. This is where the dreaded "Async load timed out after 30 seconds" comes in - it indicates that the DSF loader was so far behind that it locked up for half a minute and didn't catch up.
- The old DSF loader loads one DSF at a time, tops.
DSF Loading the New Way
X-Plane 10.40 has the new DSF loader, which both loads and unloads DSFs on worker threads to keep flight smoother. It also will load more than one DSF at a time, limited only by the requirement that adjacent DSFs not be loaded at the same time.
X-Plane 10.40 also has the option of an extended DSF scenery region for sharper terrain; with this option off, two DSFs are loaded at one time during sim boot and one or two are loaded at a time while you fly. With the extended DSF region on, up to four DSFs are loaded at once during sim boot and one or two are loaded while you fly.
The extended DSF scenery region is optional; don't use this if you're using HD meshes or you're short on RAM. The new DSF loader is always on.