Expand generated terrain with biome-driven props

world/generation/terrain_biome_definition.gd

@@ -0,0 +1,27 @@
+class_name TerrainBiomeDefinition
+extends Resource
+
+@export var stable_id: StringName
+@export var label := ""
+@export var required_chunk_tags := PackedStringArray()
+@export var forbidden_chunk_tags := PackedStringArray()
+## Larger values give this biome more territory around its seeded anchor.
+@export_range(0.1, 10.0, 0.1) var region_weight := 1.0
+@export var prop_rules: Array[TerrainBiomePropRule] = []
+
+
+func supports_chunk_tags(chunk_tags: PackedStringArray) -> bool:
+	for required_tag: String in required_chunk_tags:
+		if required_tag not in chunk_tags:
+			return false
+	for forbidden_tag: String in forbidden_chunk_tags:
+		if forbidden_tag in chunk_tags:
+			return false
+	return true
+
+
+func prop_rule_for_group(group: StringName) -> TerrainBiomePropRule:
+	for rule: TerrainBiomePropRule in prop_rules:
+		if rule != null and rule.procedural_group == group:
+			return rule
+	return null