White pixel flickering artifacts with "DitherFade" material layer

[j9liu]

This may be related to #1104, but that issue is about seeing temporal dithering artifacts with forward rendering + AA. There are actually dithering artifacts that happen with temporal rendering.

Reported on the forum here. The user sees bright white pixels flickering throughout the tileset, which are especially visible when the lighting is dark. This is with:

• Unreal Engine 5.3
• Cesium for Unreal 2.4.1
• Google Photorealistic 3D Tiles
• Temporal Super Resolution enabled in project settings (this is how it's set in the samples)
• Enable LOD Transitions on the tileset set to false

To reproduce the view, set the georeference to
Latitude: 59.908135
Longitude: 10.721472
Height: 99.238093

( Zoom in to see more clearly. From a distance it will look like you have dust on your computer. :') )

The workaround was to delete the "DitherFade" material layer from the default tileset material.

One action item is to test if the plugin version matters, since the user says it worsened with time. Engine version may matter too.

[csciguy8]

Sounds very much like,
#1359

[j9liu]

Trying to do some experimentation to resolve this issue. I made some test modifications to our ML_DitherFade Blueprint.

From what I understand, the "Fade Percentage" seems to roughly translate to the intended opacity of the tile, or the amount that the tile has faded in. I noticed that even when the Fade Percentage is 1.0, it still goes through the "Dither Temporal AA" block, which causes the flickering. Indeed when I hardcode the opacity mask to be 1.0, that flickering goes away.

So with that in mind, I tried to catch when the percentage is 1.0. If it is, I hardcode the opacity mask to 1.0

This does remove the flickering at the highest level of detail. But unfortunately, it impacts the transitions themselves, making them look a lot less smooth. (Between multiple levels of detail you can see clear "jumps" where that percentage is 1.0).

So I don't know what the fix is 😅 Ideally, that "Dither Temporal AA" block wouldn't apply dithering if the fade percentage was zero. I'll keep digging

[j9liu]

I noticed an interesting comment in "Dither Temporal AA"...

So I tried something silly by inverting the fade percentage (using a 1 - x node) ... and it weirdly works? The tilesets no longer flicker at the highest level of detail! This is true regardless of whether Enable LOD Transitions is true.

For the acutal transitions, I can't tell the difference between the previous implementation and mine. But maybe I've been staring at this for too long. 😅