Fix terrain surface texture projection

tests/terrain_projection_validation.gd

@@ -0,0 +1,60 @@
+extends SceneTree
+
+const REGION := preload("res://world/regions/starter_island_region.tscn")
+
+
+func _initialize() -> void:
+	call_deferred("_run")
+
+
+func _run() -> void:
+	var region := REGION.instantiate()
+	root.add_child(region)
+	await process_frame
+	var terrain := region.get_node(
+		"Terrain/Visual/starter_island"
+	) as MeshInstance3D
+	assert(terrain != null)
+	assert(terrain.mesh.get_surface_count() == 5)
+	assert(terrain.mesh.surface_get_name(0) == "grass_lite")
+	assert(terrain.mesh.surface_get_name(1) == "dirt")
+	assert(terrain.mesh.surface_get_name(2) == "sand")
+	assert(terrain.mesh.surface_get_name(3) == "cliff_wall")
+	assert(terrain.mesh.surface_get_name(4) == "dirt_wall")
+
+	_validate_projected_material(terrain.get_surface_override_material(0))
+	_validate_projected_material(terrain.get_surface_override_material(2))
+	for surface: int in [1, 3, 4]:
+		assert(terrain.get_surface_override_material(surface) == null)
+		assert(terrain.mesh.surface_get_material(surface) is StandardMaterial3D)
+
+	print("Terrain projection validation: PASS")
+	region.free()
+	quit()
+
+
+func _validate_projected_material(material: Material) -> void:
+	assert(material is ShaderMaterial)
+	var shader_material := material as ShaderMaterial
+	assert(
+		shader_material.shader.resource_path
+		== "res://world/materials/terrain_surface_projection.gdshader"
+	)
+	assert(
+		is_equal_approx(
+			float(shader_material.get_shader_parameter("tile_world_size")),
+			2.5
+		)
+	)
+	assert(
+		is_equal_approx(
+			float(shader_material.get_shader_parameter("blend_sharpness")),
+			6.0
+		)
+	)
+	assert(
+		is_equal_approx(
+			float(shader_material.get_shader_parameter("top_projection_bias")),
+			2.0
+		)
+	)

tests/terrain_projection_validation.gd.uid

@@ -0,0 +1 @@
+uid://cto4rc6bn0n4o