Weather: snow should not collect on mesh water (pools, ponds, fountains) #936

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opened 2026-10-22 04:04:05 +00:00 by sky_line · 0 comments

sky_line commented

2026-10-22 04:04:05 +00:00

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Snow collects on top of pool / pond surfaces made from mesh or prims ("mesh water"), not just region water (#783).

The viewer can't know an object is water, so combine a heuristic with an explicit opt-out:

Heuristic: horizontal surfaces that are transparent (alpha blend, or PBR transmission) AND have an animated texture (scrolling) count as liquid; very glossy as a weaker signal. Transparent + animated catches most pools without catching glass skylights (glass should still hold snow).
Explicit tag: an object description keyword (e.g. #nosnow / #water) and an entry in the parcel weather tag spec so scripts can mark surfaces, for anything the heuristic misses or gets wrong.
Behaviour: snow landing on a liquid surface disappears (as on region water); no snow mesh, no shader coat, and slumping never pushes snow onto it.

The decision is made when an object enters the snow maps (ingest / shelter raster), not per frame.

Snow collects on top of pool / pond surfaces made from mesh or prims ("mesh water"), not just region water (#783). The viewer can't know an object is water, so combine a heuristic with an explicit opt-out: 1. **Heuristic:** horizontal surfaces that are transparent (alpha blend, or PBR transmission) AND have an animated texture (scrolling) count as liquid; very glossy as a weaker signal. Transparent + animated catches most pools without catching glass skylights (glass should still hold snow). 2. **Explicit tag:** an object description keyword (e.g. `#nosnow` / `#water`) and an entry in the parcel weather tag spec so scripts can mark surfaces, for anything the heuristic misses or gets wrong. 3. **Behaviour:** snow landing on a liquid surface disappears (as on region water); no snow mesh, no shader coat, and slumping never pushes snow onto it. The decision is made when an object enters the snow maps (ingest / shelter raster), not per frame.

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2026-10-22 04:04:05 +00:00

sky_line added this to the Slipstream project

2026-10-22 04:04:05 +00:00

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sky_line/Slipstream#936

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