REX Atmos CORE: the critic who came back and said "I Was WRONG"

In August 2025, a YouTuber called Easyjetsimpilot published a first look at REX Atmos CORE and did not like it. Twenty-two thousand people watched him say so. The AVSIM thread turned into an argument about whether he had even used the thing properly — one poster called the video a disgrace, another said it was obvious he was yanking sliders from one extreme to the other without noticing how they interact.

Then he made a second video. It is called "I Was WRONG About Rex Atmos Core in MSFS 2024". It has twenty-eight thousand views, six thousand more than the takedown.

That reversal is the most useful single fact about this product, and it cuts both ways. Atmos CORE is genuinely good, and it is genuinely awful to learn. Everyone who ends up liking it goes through the same arc: an hour of moving sliders that appear to do nothing until suddenly they do too much, then a downloaded community preset, then the moment the horizon stops looking like a video game. The people who never make it through that hour write reviews saying it is basic and unintuitive. Both groups are describing the same software accurately.

Atmos CORE is a year old this week — released 21 August 2025, $14.50, MSFS 2024 only. It is not a weather engine despite the name on the page, and it is not a ReShade filter despite what people keep saying in YouTube comments. It sits inside the simulator and changes how the atmosphere is rendered: Rayleigh scattering values, scattering height, light phase functions, particulate haze, ambient tinting. What it does not do is decide what the weather is. That job belongs to Asobo Live Weather, to a saved preset, or to ActiveSky — or to REX Weather CORE, which was billed as "upcoming" at launch and, twelve months later, has never been mentioned again.

We read twenty sources for this review: four store listings and their rating spreads, REX's own product page, news archive and changelog, one written review, four forum threads running from July 2025 to 5 May 2026, five video reviews including both halves of the recantation above, and two launch news pieces.

What you are actually buying

One small application, three modules, and a lot of sliders.

Price (REX Store)	$14.50 USD
Upgrade from Atmos MSFS 2020	50% off, about $7
simMarket / Orbx / Aerosoft	€12.41 · A$22.27 · $14.50
Simulator	MSFS 2024 only
Current version	8.1.2025.1210, Technical Update 1.0
Released	21 August 2025
Download size	75–112 MB depending on store
Internet	Required for install, registration and operation

The three modules are Weather (visual tuning of whatever live conditions you already have, plus a builder for custom scenarios you can share), Atmosphere (scattering height, Rayleigh RGB, phase functions, and a particulate engine for haze, dust and moisture), and Enviro (ambient light tinting and global tone, per channel or locked together). Presets save locally and to REX's cloud, and can autoload at launch.

Two things to understand before you spend the money. First, there is no cheaper or older version to consider — Atmos for MSFS 2020 is a different product for a different simulator, and owning it just gets you half off this one. Second, on 20 July 2026 REX flattened its entire catalogue to $14.50 a product, so the Atmos 2020 licence that unlocks your discount now costs the same as the thing it discounts.

What the community consistently praises

The visual result, and it is not subtle once configured. On the official MSFS forums, davidkenobi posted a side-by-side comparison on 29 August 2025; Yuudai5178 replied the next day calling the Atmos images more natural and the defaults "too overblown"; Floek2013 came back on 14 September preferring defaults in dramatic light but Atmos in daylight. That is what a real visual improvement looks like in a forum — people arguing about which conditions it wins in, not whether it does anything.

Threshold's Olai Dreisbach, reviewing on 2 February 2026, put a specific engineering claim behind the impression: Atmos CORE measurably reduces the "sepia mask" that afflicts MSFS 2024's night visuals. Not a matter of taste — a named rendering fault that this product improves. He also found that "the air gains depth and substance" and horizons blend more naturally.

Second, and this matters because the internet keeps getting it wrong: it is not a filter. Canbey Mehmet's simMarket review of 1 September 2025 is the clearest explanation anyone has written of the difference — ReShade and NVIDIA filters apply one treatment to the whole frame, whereas Atmos changes the sky and the sunrays themselves so that they light the terrain and objects differently. REX makes the same argument on their FAQ. In this instance the marketing is right and the sceptics are wrong.

Third, performance. Alessandro, simMarket, 30 August 2025: minimal impact on frame rates. REX's own FAQ concedes only a brief pause while a slider change is processed, after which frame rates return to normal. Across twelve months and every source we read, not one person complained about the performance cost. For a product that hooks the rendering pipeline, that is worth saying out loud.

Fourth, price. At $14.50, and roughly $7 for Atmos 2020 owners, this is one of the cheapest ways to change how MSFS 2024 looks. Lázaro, whose simMarket review is otherwise the harshest technical critique in the record, still opened it with "It's a simple buy for only 15 Euro."

And fifth, support — when you get through to it. MichaelEleven7 could not launch the application at all on 10 January 2026, contacted REX, and reported back on 1 February that he had been walked through the fix on a Microsoft Teams call by, in his words, a very nice guy from Canada. He then went on to call the atmospheric scattering effect a huge difference and well worth the money.

What keeps coming up as a problem

The sliders — still open, and this is the review's central complaint

Two independent sources, five months apart, measured the same defect and reached almost the same number.

Lázaro, simMarket, 29 August 2025, one week after release: the light settings in the Enviro tab use "like 2-3% of the range with the rest giving unusable results", and he asked for manual numeric entry. Threshold, 2 February 2026: slider ranges cover unnecessarily wide areas with the functional zone occupying only ten to twenty per cent of the control, so that "even a tiny slider movement can dramatically alter the image, yet the sliders move in increments that are far too large".

That is not a matter of taste and it is not a learning curve. It is a control that is calibrated wrong, and it is the single reason the first-look videos went badly.

No manual — still open

Lázaro again, 29 August 2025: "Give me a tutorial or a manual to explain stuff. If there is a manual, I couldn't find it in the app." Threshold found that the manual offers minimal guidance on what the functions actually do. On AVSIM on 20 October 2025, John-Allen was told his crash was caused by a missing Edge WebView2 dependency and replied, reasonably, that he had never heard of dependencies and is not a programmer. A product whose controls are this sensitive needs documentation, and there is none worth the name.

Presets are static — still open, and it was the top request in launch week

This is the one that turns people away before they buy. Bobsk8, AVSIM, 27 August 2025: if you do not want it to look the same on every flight, you have to change the preset yourself. AnkH the same day: he does not want to adjust settings for each time of day, each weather condition and each season. Alti, 28 August 2025, in the most constructive version of the complaint, described exactly what he wants — save profiles for rain, haze, snow, morning, evening, and have the program react to the simulator's clock and conditions and transition between them — and concluded that without it, REX had not convinced him. Yuudai5178 on the MSFS forums was waiting for "dynamic mode" on 30 August 2025. bobcat999 noted the same day that Atmos loses its balance when the sim moves from day to night.

Gilandred replied on 27 August 2025 that the developers had said they wanted to add dynamic changes in future. A year on, REX's product page still lists "in-flight dynamic evolution" under Future-ready.

Preset handling is unreliable — still open, and getting worse in the record, not better

Onur's simMarket review of 22 March 2026 is the most recent substantive report we have: presets sometimes fail to apply when switching between them, and profiles have to be reselected every time the program launches. That is seven months after release and three months after the only update.

One update in twelve months — still open

REX's news archive is public and complete. Atmos CORE was announced 1 August 2025, released 21 August 2025, and updated exactly once: Technical Update 1.0 on 29 December 2025. Everything REX has published since is marketing — a screenshot contest winner on 9 February 2026, a 30% sale on 17 April, a preset initiative on 7 June, a price cut on 20 July.

The gap matters because of what that one update contained. It restored SU4 compatibility and fixed custom weather rendering in all three modes — METAR, Simple and Advanced — plus a required description field that prevented presets being saved at all and a UI validation fault that stopped the Save button enabling. Those are not polish items. For part of autumn 2025 the weather half of a weather product did not render correctly and you could not reliably save your work.

The SU5 answer never came in public — still open

On 30 April 2026 REX posted to their Discord, quoted verbatim into the MSFS forums thread on 5 May by WhaleCowboy: "We are currently testing SU5 with the current official release of REX Atmos Core to confirm full functionality. All customers may continue using the application until further notice. We will provide an update on Monday along with an official statement if any issues are identified."

That Monday was 4 May 2026. As of 19 August 2026, REX's public news page contains no SU5 statement of any kind, and no software update has followed. It is possible the promised statement was posted on Discord, which is closed to us — but a buyer reading REX's own website today has no way of knowing whether the product they are about to purchase is current with their simulator. That is a fixable problem and it has not been fixed in three and a half months.

Performance and stability

Frame rates: a genuine strength, and unanimously so. Nobody in any source we read reported a performance cost.

Getting the thing to launch: a genuine weakness, and repeatedly so.

The worst stretch was October 2025. Atmos CORE would open and close after about six seconds. John-Allen reported it on AVSIM on 19 October after a complete uninstall and reinstall; Bigmack had the same fault the next day, posted on REX's Discord, was told to submit a ticket, and heard nothing back. Two causes emerged, neither documented by REX: a missing Microsoft Edge WebView2 runtime, which Sparkrite traced through Event Viewer on 20 October, and a versioning mess that agutz untangled on 22 October — the SU4-beta-compatible build was time-limited, it expired, users were pushed back onto a build that did not work with SU4 beta, and REX then revoked the limit and asked everyone to re-download.

Launch failures continued past the fix. MichaelEleven7, 10 January 2026: crashes on loading, on the official stable release. KarlYoghurt, 17 January: "Same problem, client crash." Zeanuck, 31 January: a "not a verified user" error despite valid registration, no field to enter a serial, and ten minutes from asking for a refund — while also objecting to being asked to grant the application firewall access. SierraBravo8594, 1 February: half a day of installing and uninstalling before discovering the cause was Windows running a secure DNS.

Interference with the simulator's own weather is rare but real. MichaelEleven7, on balance a fan, noted it happened once across many flights. MichaelBGL reported on 4 February 2026 that injected clouds vanished after five seconds, and resolved it himself the next day by reinstalling and disabling his VPN client.

The pattern is consistent: the software is fragile about its environment — WebView2, DNS, firewall, VPN — and REX does not document any of it.

Who should buy it

If you already own REX Atmos for MSFS 2020 and liked it: buy it, at roughly $7. You already know what the sliders do and you already know you enjoy this kind of fiddling. There is no cheaper way to move that habit into MSFS 2024.

If you enjoy tuning, download community presets, and take screenshots: buy it. This is the profile the record is unambiguous about. The people who use shared presets as a starting point are the ones who say it transformed their sim, and Easyjetsimpilot's second video is essentially a public demonstration of that transition.

If MSFS 2024's night lighting bothers you: buy it. Threshold's finding on the sepia mask is the most concrete technical benefit anyone has documented, and $14.50 is little to spend on a specific fault you already notice.

If you want your sim to look better without ever opening another application: do not buy this. You will load it once, drag the Enviro sliders through their unusable ninety per cent, decide it is broken, and be right about your own experience. The dynamic behaviour that would make this a set-and-forget product has been listed as "upcoming" for a year. Wait for it, or spend the money elsewhere.

If you are buying it expecting a weather engine: do not. It renders and tunes weather; it does not source it. If you want real-world weather injection you still need Asobo's live weather or ActiveSky, and Atmos CORE will sit on top of either.

If you are still on MSFS 2020: this is not for you. It is 2024 only. The 2020 Atmos is a separate purchase, now also $14.50.

Where it stands today

The honest summary of twelve months is that REX built a good renderer and a bad instrument panel, and then stopped. The engine-level approach is real, the visual gain is real, the performance cost is not, and the price is fair. Set against that: sliders whose usable range is a few per cent of their travel, no documentation, static presets, a fragile launch sequence that trips over WebView2 and DNS and VPNs, one software update since August 2025, and a promised SU5 statement that never appeared anywhere a prospective customer can read it.

The store numbers are unusually informative here, and for once the badge is harsher than the arithmetic. simMarket displays a flat "4" across eight reviews; the actual spread is four five-star, two four-star and two three-star, which averages 4.25. Look at what the middle ratings say and the split is perfectly clean: the three-star and four-star reviewers all praise the output and all complain about the interface. Maximilian, 16 September 2025, scored it 2.5 out of 5 in his own text while conceding that a good configuration produces beautiful, distinctive atmospheres. João, 15 March 2026, put it in eight words: a good product behind a bad user experience.

So: buy it if you are the kind of person who will spend an evening with sliders and a community preset library, and skip it if you are not. That is a real recommendation, not a hedge — the two groups genuinely get different products for their $14.50. And if REX ever ships the dynamic, weather-reactive presets they described a year ago, this review's score goes up by half a point on the day it lands, because everything else is already there.