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secondlife/viewer-private#230: Amend terrain loading test plan

meow-7.2.2
Cosmic Linden 2024-04-26 12:03:19 -07:00
parent 6f51d909a2
commit 08e012b4fa
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doc/testplans/terrain_loading.md
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- Texture terrain should load
- PBR terrain should load if enabled
# Terrain Loading
## Behavior overview
- Texture terrain should load if applied
- PBR terrain should load if applied, even if the feature flag is disabled
- Related subsystem: A change to the PBR terrain loading system may affect the texture terrain loading system and vice-versa
- Related subsystem: Minimaps should load if terrain loads (may take longer)
- Related subsystem: Minimap should load if terrain loads
- They may not finish loading at the same time
## Implementation details
This section is provided mainly for clarification of how the terrain loading system works.
The simulator sends 4 terrain composition UUIDs to the viewer for the region. The viewer does not know ahead-of-time if the terrain composition uses textures or materials. Therefore, to expedite terrain loading, the viewer makes up to 8 "top-level" asset requests simultaneously:
- Up to 4 texture asset requests, one for each UUID
- Up to 4 material asset requests, one for each UUID
It is therefore expected that half of these asset lookups will fail.
The viewer inspects the load success of these top-level assets to make the binary decision of whether to render all 4 texture assets or all 4 material assets. This determines the choice of composition for terrain both in-world and on the minimap.
The minimap also attempts to wait for textures to partially load before it can render a tile for a given region:
- When rendering texture terrain, the minimap attempts to wait for top-level texture assets to partially load
- When rendering PBR material terrain, the minimap attempts to wait for any base color/emissive textures in the materials to partially load, if they are present
We don't make guarantees that the minimap tile will render for the region if any aforementioned required textures/materials fail to sufficiently load. However, the minimap may make a best-effort attempt to render the region by ignoring or replacing data.