Improvement to terrain/imagery tile load ordering #4613
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From highest to lowest priority: 1. Tiles blocking refinement. 2. Tiles that are being rendered. 3. All other tiles.
Any chance you could make an annotated gif or video of this for outreach purposes? |
| // and because we (currently) must have all children in a quad renderable before we | ||
| // can refine, this pretty much means tiles we'd like to refine to, regardless of | ||
| // visibility. (high) | ||
| // 2. Tiles that we're rendering. (medium) |
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It might just be terminology, but, for my understanding, why are "tiles that we're rendering" in the load order at all? Aren't they already loaded?
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We can render a tile before it's fully loaded. For example, if we add an imagery layer, terrain tiles don't disappear or unrefine while we're loading the new layer. Also upsampling (for better or worse) means that we can render terrain tiles before the terrain data is completely loaded.
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Gotcha, so it's tiles that we're rendering and are pending an update.
| var i = 0; | ||
| var tile; | ||
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| for (i = tileLoadQueueHigh.length - 1; i >= 0; --i) { |
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Instead of having three loops here, can we just move this to a utility function and pass in the queue?
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Is it possible to add any other reasonable unit tests to verify that the right tiles are in the right queue? |
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@lilleyse can you also review this? It is potentially relevant to 3D Tiles. |
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Thanks @kring, just those comments. |
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These changes here and in #4616 look good. I don't much else to add but to confirm that everything does feel snappier. |
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I'm closing this because #4616 contains all of these changes plus some improvements, and if you actually merge this first, as I originally suggested, you'll probably get merge conflicts. |
This change groups tiles that need loading into three tiers:
high- Tiles that are blocking refinement (their parents don't meet SSE, but we can't refine because these tiles are not renderable yet)medium- Tiles that were selected for rendering this frame.low- All other tiles, such as parent tiles we refined and extra tiles needed to complete quads.Within each tier, tiles are loaded in traversal order, which currently is not ideal but improving that will be a separate PR.
It's surprisingly hard to benchmark reliably, but performance seems snappier, and if nothing else this strategy is a lot more justifiable than the "just load in traversal order" that we were doing before.
In TerriaJS and probably lots of other applications, it's common to have the camera in a particular place and everything loaded, and then enable another imagery layer. This PR makes that scenario noticeably quicker because it strictly loads the new layer on all the visible tiles first, before loading any extraneous nonsense. You can easily try this out in Viewer by switching the base map after the view is loaded.