**Title:** Dynamic Liquid

**Description:** 

**Details:**
This mod implements a simple approach to making the various liquid node types (water, lava) behave in a more realistic manner. In a nutshell, it sets an Active Block Modifier running for liquid nodes that implements the following behavior:

* If there is a "flowing" or air node below a "source" liquid block, swap the liquid block with the node below it (ie, the liquid drops)
* Else swap with a random flowing or air node beside it.

This causes "source" blocks for liquids to randomly shuffle around when they don't completely fill a horizontal layer, and causes them to drain rapidly down holes or flow rapidly down hillsides. Normal "flowing" behaviour is unchanged so even though this mod is just moving cubes around the surface of the water looks reasonably smooth. The ABM only runs for blocks that are adjacent to flowing nodes and does very few calculations so it's also reasonably lightweight - I'm essentially borrowing the engine's built-in liquid flow detection to determine when my own code needs to run.

Each type of liquid can have this behaviour enabled independently of each other. By default lava is configured to flow more slowly than water, but this can be changed in the mod's settings.

## Damp Clay Counters Ocean Loss

If basic water is set as dynamic, it loses its "renewability" - water nodes don't replicate like they normally do. If you are concerned about the global water level dropping over time as water pours down into undersea caverns, or just generally don't like the idea of water being a finite resource (even with an ocean's worth to start with), this mod includes an optional feature that turns natural clay deposits into "springs". Clay deposits get an Active Block Modifier that checks if there's air or shallow water above them and refills them with newly spawned water source blocks.

If this clay is dug out by players and reconstituted into clay blocks elsewhere, the "spring" behaviour won't occur for these - it only happens for clay spawned by mapgen while this feature is enabled. (In technical terms, when clay springs are enabled the map generator replaces generated clay with an otherwise identical "damp clay" node type that drops regular clay when dug. The ABM only affects this "damp clay" node type.)

There's also a "spring" block that's available only via the creative menu or /give command. This block has an ABM that ensures there's always a single block of water generated directly above it, regardless of where the block is placed.

Note that other than this clay spring feature and the override of water's "renewability" this mod doesn't affect any default node definitions, so any other mods dealing with liquids should still function as they did before. If you disable any of the liquid types they will just "freeze" in whatever position they were in at the time.

## "Flow-through" Blocks

There are many blocks in the game that one would think should not serve as an impenetrable barrier to water flow, but which do. For example: metal bars, grass, leaves. The "flow-through" feature of this mod makes them permeable, allowing water_source and lava_source blocks to "teleport" from one side of a flow-through block to the other. Liquid source blocks will only teleport through a single layer of flow-through node and only in the cardinal directions.

Other mods can mark blocks as flow-through by adding them to the "flow_through" group.

## Lava/Water Interaction

Due to the way default lava/water interaction works a single block of lava_source would be able to wander endlessly around on the surface of the ocean turning the uppermost layer of water into stone. Similarly, a single block of water_source could wander around on the surface of a lava pool turning the uppermost layer into obsidian. This is an undesirable outcome so the dynamic_liquid mod includes a more sophisticated replacement to the default lava-cooling ABM.

lava_flowing nodes are now eliminated entirely by nodes marked cools_lava, they do not leave behind default:stone. This means that infinite stone generation is no longer possible using arrangements of lava and water.

lava_source nodes are turned into obsidian only by water_source nodes; water_flowing nodes are eliminated by lava_source nodes without affecting them. The water_source node is destroyed in the process. This means that if you want to cool a large amount of lava you're going to need a correspondingly large amount of water.

For modders, you can now fine-tune the effects of blocks on lava (and vice versa) using the following groups:

* "group:dynamic_cools_lava_flowing" - causes lava_flowing nodes to vanish. The old "group:cools_lava" has this effect.
* "group:dynamic_lava_flowing_destroys" - causes lava_flowing nodes to destroy nodes belonging to this group.
* "group:dynamic_cools_lava_source" - causes lava_source nodes to turn into obsidian. The old "group:cools_lava" does *not* have this effect.
* "group:dynamic_lava_source_destroys" - causes lava_source nodes to destroy nodes belonging to this group.


**Tags:** environment
**Repository:** https://github.com/minetest-mods/dynamic_liquid
**License:** MIT