Propellers and reprojection

Here’s a blog post that I found while looking into this issue, it explains it from a modeler’s view:

The money quote:

So what I want to see is a transparent disc of the correct propeller colour(s), with the colour density at each radius matching the relative amount of prop blade and empty space at that radius.

(Not sure if that’s possible with the tech we have, but can the disc have realistic reflections?)

There’s another argument for “transparent disc” style prop animations: even when you turn off reprojection, even if you’re flying on a flat display, the Asobo graphics engine seems to produce a distortion effect. Go flying in VR on a cloudy day at dawn or dusk, and try setting the prop rpm so the prop animation rotates slowly (e.g. in the JustFlight Arrow: 2400-2500 rpm). The distortions are most visible wherever there’s contrast. This is what triggered me to look into this issue: I had turbulent cloud layers ahead of me which were bathed in red sunlight, and the whole cloud mass was wobbling and writhing. (At the time, I didn’t realize that a different rpm setting would’ve mititgated the effect.)

When using new Motion Reprojection available from 22.5 fps as new 106 version for OpenXR, propellers produce plenty of artifacts, specially at cloudy weather and other planes tags. These kind of mods (10 Propeller Mods for the FS2020 Standard Edition: NEW! - Microsoft Flight Simulator (2020) - The AVSIM Community) solve the issue quite well. Can MSFS provide solution for this at all planes without need for mods?

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It’s not only the propellers. With motion reprojection everything becomes blurry and shimmering. It looks horrible. I tested it a few times and always quickly disable it. Also it adds additional CPU load so you actually loose quite a lot of real frames.

I use automatic render scale in OXR (force render scale unchecked) and 100% TAA in MSFS. Looks great and is smooth enough (2080Ti, R5900X).

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Don’t agree. MR is awesome, and provided an awesome immersion. But it only will work if you can stay safely 99% of time above 22.5 fps (before 106 version 30 fps were needed). If using high resolution VR headsets like Reverb G2, a very powerful PC rig is needed (3080/3090), and even that render resolution has to be decreased some (from 90% to 80% with my 3080). But awesome smoothness is worthy IMHO. Small artifacts can appear around wings, but they are not a problem. Large artifacts at propellers at cloudy weather and other planes tags are very annoying…

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Otherwise, it is very easy to fix it yourself:

  1. Open the aircraft Texture folder (usually TEXTURE)

  2. Locate the filenames with “PROP” something (most likely) and extension .DDS.

  3. Sometimes there are “SLOW” and “FAST” variants, ignore any “SIDE” variant.

  4. And/or you might want to also look for those named “BACK” or “_B” which usually are the propeller textures seen from the cockpit.

  5. Copy each of these for backup then open each of these with Paint.net

  6. In the Layers pane, click on the Wrench tool and change Opacity between 64 and 127*
    Screenshot 2021-05-13 202433 Screenshot 2021-05-13 202541

  7. Save (CTRL+S) and make sure the first drop down on the top left is set to DXT5 format

  8. Then close (CTRL+W).

*most of the time you’d try 64 first and see

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Wow!! MANY thanks. Will try with my spitfire…

What saving parameters must I use? image

Paint should save in the same format as the source, for the rest, it doesn’t matter much for a highly transparent prop texture. Just keep the default and press OK to get started with (provided you’ve made a backup of your textures just in case you want to restore them latere)

This update just doesn’t work with my setup. I get CTD every time I try, and the weird wobbling is far more distracting than whatever decrease in jitter might be happening. I don’t experience much if any jitter with reprojection off. My issue is driver timeout errors with Radeon drivers. I have a 6800 card fully powerful enough for acceptable FR’s, but can’t avoid CTD without lowering settings to 70/70 in render scaling and all other sim settings to medium or low. Radeon drivers are ■■■■ for VR.

I tried to edit Just Flight JF_PA28_Arrow prop texture with Paint.net. However, when saving, it requires to choose one of many formats like:

  • BC1 (Line, DXT1) - when I save in this format (1st on the list) - I just get the empty backgorund
  • BC2
  • BC3
    and many more.
    Unfortunattely Paint.net is not informing what was the orignsal file type. Which format should I choose to save?

In practice just CTRL+S then ENTER works fine for me.

I usually don’t change anything because I suppose the one it has selected in the “saving” panel is already appropriate for the texture type (with or without transparency is the most determining factor here). In most cases for the propeller you’d use DXT5 and this is fine.

Seems like a working choice for saving:

I still need to identify which one requires editing:
image

With my suggestions, this would be: PROP_BACK and PROP_SLOW_B

Before and after:
image

Now I have to test in the sim.

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night and day!

I only use 64 by default now on all the propellers I want to change. Did you use 64 as well?

64, as you recommended. Defaul is totally unrealistic, even without reprojection. I fly in RW, the propeller is barelly visible, more like a faint blurry disk than a strobo-blades. I don’t have a camera shutter in my eyes, so the strobe effect is not visible in RW (anybody can check it looking at the fast rotating home/office fan).

Aurel at JustFlight forum even recommended a texture showing a bladeless disc:

image

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This is a great idea! I modified my PA28 textured in Photoshop with NVidia DDS plugin, basically does the same thing. You need to do all textures that have BACK or _B or similar. Those are the ones yo usee from the cockpit.

But it’s just as easy to do a bladeless disc. Will look just are realistic, if not more so, and should not produce any artifacts at all, hopefully. With my modified texture, I sill see some artifacts very rarely.

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I realized I’ve commented in the “My VR Index” topic but not here, so here is the info, so that it consolidates in the relevant topic:

ref: My 2070 SUPER VR settings and suggestions (Index - SteamVR) 🟢 - #556 by CptLucky8

The “hack” therefore is nothing else than raising the transparency of the rotating blade texture so that it has lees impact on the pixels. I’ve found empirically that changing the opacity of the texture to 64/255 is very effective in practice.

Besides, although it sounds like a “hack” I see this more as a needed change even in 2D: your eyes IRL don’t see the stroboscopic illusion FS2020 is rendering, only a camera is capturing such illusion IRL. In turn, in changing the transparency you not only solve and workaround the limitations of the motion smoothing technology, but you also cure the inaccurate representation (IMHO) of a rotating blade in the game.

Having said this it wouldn’t be hard for the game to do this for you automatically though:

  • Enforce that aircraft modelers tag their rotating blades object as “rotating blades” (which they already do if I’m not mistaken so that the game can choose among a set of more or less blurry textures ‘matching’ the rotation speed)

  • When in VR, automatically change the alpha transparency of the texture like we’re manually doing otherwise.

In the meantime…

https://flightsim.to/file/20109/vr-friendly-prop-mod-for-jf-turbo-arrow-s

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All the ones I’ve done so far.

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