Liquid not rendered properly on top of Airflow Tiles or Solar Panels (+how to fix)

this is NOT a sim bug, the sim works perfectly fine , is however entirely irrelevant for this issue as it has nothing to do with rendering.

its more of a quirk/bug in how the liquid shader works. in short, the different border thresholds that affect the rendering of these liquid tiles overlap with each other, leading to the liquid not rendering.

the top border threshold of the liquid rendered is determined by the mass of the tile, the less mass, the higher the distance from the top border of the tile.

normally the liquid shader connects to the center of a solid tile (you can see that sometimes with poi doors or the modded airlock door).

this can obviously not be done for tiles that are a gas ( vacuum counts as gas ), so no connecting to the center if the tile + a minimum buffer in the bordering liquid tile is applied. this (rather generous) buffer offset is put there to prevent the liquid from clipping into the gas tile.(this is what you describe as "falling", its technically not falling but it just appears during that as liquids fall always in gas)

now, these 2 factors collide here:

assuming there are 100px of height in the tile

the liquid mass defines the liquid height to f.e. 80px below the top tile border for a low mass liquid.

the "prevent liquid rendering inside gas tiles" part however sets a minimum of f.e. 25px from the tile border that is adjacent to this tile for the lower border of the liquid, making both exclusion zones overlap with each other,  0-25px blocked by tile offset from the gas below, 20-100px blocked by low mass, resulting in no liquid being rendered.

the uneven "blobs" exist because, while these offsets are a set number, the liquid shader applied some variance when rendering the borders to not have straight lines

Edited July 12, 2023 by SGT_Imalas

I see. I couldn't find the place where liquid drawing was handled in the C# code (the few placer that seemed relevant are apparently actually unused code), so I assumed it was the C++ sim code that handled the liquid drawing.

That said, even though I got wrong where this is handled, I don't see how it changes much what I said about how it could be improved.

2 hours ago, SGT_Imalas said:

normally the liquid shader connects to the center of a solid tile (you can see that sometimes with poi doors or the modded airlock door).

this can obviously not be done for tiles that are a gas

Obviously? This is a screenshot of an Airflow Tile hacked to make the tile solid ("simCellOccupier.doReplaceElement = true;").
 

If I look hard, I can see the water inside the tile, but this is still a big improvement over the current situation. And unlike the floating or invisible water, I could even convince myself that this is actually correct. So this in fact can be done for gas tiles that are LiquidImpermeable buildings, wherever it is that this is handled.

In fact, since any larger amount of water cannot ever(?) have gas below it or to the side of it for more than a split of a second, liquid could probably always be made to reach into gas tiles that are not above, and it would look fine. But, really, either way, even if imperfect, would be an improvement over what it is now.

EDIT: With Solar Panel this is somewhat ugly, although I'd still consider that to be an improvement. Presumably this could be handled by reaching only very little into LiquidImpermeable building tiles (which would also handle the mentioned POI or Airlock mod door drawing).

Edited July 12, 2023 by llunak

31 minutes ago, llunak said:

Obviously? This is a screenshot of an Airflow Tile hacked to make the tile solid ("simCellOccupier.doReplaceElement = true;").

yes obviously, as these tiles are now solid tiles and dont allow any form of gas inside of them.

airflow tiles (and the vacuum of solar panels) are always handled as the gas that occupies the cell, not the tile building, as they cannot physically occupy the tile they are in (since that would break the "airflow" part of them)

If you would change the shader to behave like that it would break every single border to all gas tiles, as the shader can only check if the tile is a gas or not

Edited July 12, 2023 by SGT_Imalas

6 minutes ago, SGT_Imalas said:

yes obviously, as these tiles are now solid tiles and dont allow any form of gas inside of them.

airflow tiles (and the vacuum of solar panels) are always handled as the gas that occupies the cell, not the tile building, as they cannot physically occupy the tile they are in (since that would break the "airflow" part of them)

So? I wrote "hacked" because it's a temporary hack to show how that would be rendered, not because I suggest that as a solution.

6 minutes ago, SGT_Imalas said:

If you would change the shader to behave like that it would break every single border to all gas tiles, as the shader can only check if the tile is a gas or not

Which is why my actual suggestion was to extend the place to check whether a tile is solid or LiquidImpermeable. Surely the shader can check more if made so.

Just for the record, I've implemented a workaround for this in a mod https://steamcommunity.com/sharedfiles/filedetails/?id=3163125334 , which handles it by changing the tile type.

Changed Status to Fixed