Billboard jitters when modifying imageSubRegion

[syzdev]

I want to use CallbackProperty to modify imageSubRegion to implement dynamic Billboard, but I find that when the width and height of Billboard.image are large enough, Billboard will jitter after modifying imageSubRegion. And the larger the width and height of Billboard.image, the more violent the jitter.

I implemented a simple case to reproduce this problem, in this case I repeatedly drew a 128*128 image whiteShapes.png on the Canvas, and then used the CallbackProperty to modify the imageSubRegion to get a BoundingRectangle at different positions (Although different BoundingRectangle will get the same image content).

In the picture below, the width and height of Canvas are 6400. The picture has been drawn for a total of 2500 times, and you can see that the jitter is very obvious.

In the picture below, the width and height of Canvas are 512. The picture has been drawn for a total of 16 times, and you can see that it is very calm.

You can modify NumberOfRepeats in the sample code to see different situations. Jitter starts when NumberOfRepeats >= 5 in
my computer.

Sandcastle example: Cesium Sandcastle

Browser: Latest versions of Chrome

Operating System: Windows 11

[ggetz]

Thanks for the report @syzdev.

I'm seeing some flickering at a size of 512, although it's less apparent than the flickering at larger sizes.

I implemented a simple case to reproduce this problem, in this case I repeatedly drew a 128*128 image on the Canvas, and then used the CallbackProperty to modify the imageSubRegion to get a BoundingRectangle at different positions.

Would you mind explaining your use case? There may be a better way to achieve a similar end result.

[syzdev]

@ggetz Thank you for your attention!

I want to add dynamic images to the scene (such as .gif), and there are currently two implementation methods that I can think of:

1. HTML Overlays: However, this method places dynamic images outside the scene and cannot interact with the scene.
2. Billboard: The inspiration for all of this comes from #2319. Although this discussion has been going on for a long time, the implementation method is still feasible, but the problem described above may occur when the Canvas size is too large.

In the example provided by @mramato, due to the smaller image size and fewer frames, the Canvas size ultimately handed over to Billboard was not large, so this issue did not occur.

[ggetz]

Got it, thanks @syzdev!

I think is likely something we'd address as part of support for #2319. I would suggest moving this discussion there.

We're also happy to take intermediate PRs if you have the bandwidth to contribute. 😄

[syzdev]

Note: This may be a precision loss issue due to compression of texture coordinates.