Add water in a slightly hacky way

World.gd

@@ -0,0 +1,20 @@
+extends Spatial
+
+
+const ray_length = 2000
+
+
+func _physics_process(delta):
+	if Input.is_mouse_button_pressed(1):
+		# If the left mouse button was pressed, cast a ray towards the mouse position
+		var mouse_pos = get_viewport().get_mouse_position()
+		
+		var camera = $LerpedFollow/LerpedCamera
+		var from = camera.project_ray_origin(mouse_pos)
+		var to = from + camera.project_ray_normal(mouse_pos) * ray_length
+		
+		var result = get_world().direct_space_state.intersect_ray(from, to)
+		
+		if not result.empty():
+			# If there was a collision, set the depth of the water at that position
+			$Water.set_depth_at_position(result.position, 0.0)

World.tscn

@@ -1,4 +1,4 @@
-[gd_scene load_steps=23 format=2]
+[gd_scene load_steps=25 format=2]
 
 [ext_resource path="res://Player.tscn" type="PackedScene" id=1]
 [ext_resource path="res://Planets.gd" type="Script" id=2]
@@ -11,6 +11,8 @@
 [ext_resource path="res://Resources/gas_planet_flowmap.png" type="Texture" id=9]
 [ext_resource path="res://Resources/gas_planet_base.png" type="Texture" id=10]
 [ext_resource path="res://LerpedFollow.gd" type="Script" id=11]
+[ext_resource path="res://addons/interactive_water/Water.tscn" type="PackedScene" id=12]
+[ext_resource path="res://World.gd" type="Script" id=13]
 
 [sub_resource type="CubeMesh" id=1]
 size = Vector3( 10, 0.5, 10 )
@@ -101,6 +103,7 @@ glow_strength = 1.1
 glow_bloom = 0.1
 
 [node name="World" type="Spatial"]
+script = ExtResource( 13 )
 
 [node name="MovingPlatformPivot" type="Position3D" parent="."]
 transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, -125, 37, 60 )
@@ -204,3 +207,7 @@ target_paths = [ NodePath("../EnemyPos1"), NodePath("../EnemyPos2") ]
 
 [node name="Player" parent="." instance=ExtResource( 1 )]
 transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 3, 0 )
+
+[node name="Water" parent="." instance=ExtResource( 12 )]
+transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, -66, -50.5288 )
+plane_size = 200.0

addons/interactive_water/PersistentShaderTexture.tscn

@@ -0,0 +1,21 @@
+[gd_scene load_steps=2 format=2]
+
+[ext_resource path="res://addons/interactive_water/WaterHeights.gd" type="Script" id=1]
+
+[node name="PersistentShaderTexture" type="Node"]
+script = ExtResource( 1 )
+
+[node name="Viewport" type="Viewport" parent="."]
+size = Vector2( 1, 1 )
+transparent_bg = true
+handle_input_locally = false
+hdr = false
+disable_3d = true
+usage = 0
+render_target_v_flip = true
+render_target_update_mode = 3
+
+[node name="Texture" type="ColorRect" parent="Viewport"]
+margin_right = 128.0
+margin_bottom = 128.0
+rect_min_size = Vector2( 128, 128 )

addons/interactive_water/Water.gd

@@ -0,0 +1,71 @@
+extends Spatial
+
+
+# Saves every frame as a PNG in the project directory. Use for debugging (with caution)
+export var output_debug_textures := false
+export var first_output_frame := 0
+
+export var plane_size := 2.0
+
+var _frame_number := 0
+var _positions_to_set = []
+
+
+func set_depth_at_position(pos: Vector3, depth: float):
+	# Transform the global position into 2D points on the water surface with values between 0 and 1
+	pos -= translation
+	
+	var position_2d = Vector2(pos.x, pos.z)
+	
+	position_2d += Vector2(plane_size, plane_size) / 2.0
+	position_2d /= plane_size
+	
+	if position_2d.x < 1.0 and position_2d.y < 1.0 \
+			and position_2d.x >= 0.0 and position_2d.y >= 0.0:
+		_positions_to_set.append([position_2d, depth])
+
+
+func _ready():
+	$WaterMesh.mesh.size = Vector2(plane_size, plane_size)
+	
+	# Apply the scale and positioning to the collider
+	$WaterMesh/StaticBody.scale.x = plane_size / 2.0
+	$WaterMesh/StaticBody.scale.y = plane_size / 2.0
+	$WaterMesh/StaticBody.scale.z = plane_size / 2.0
+	
+	$WaterMesh/StaticBody.translation.y = 0.6 * 40.0
+
+
+func _physics_process(delta):
+	# Get result of previous frame
+	var result = $WaterHeights.get_texture()
+	
+	# Set it as the data of the water mesh
+	$WaterMesh.material_override.set_shader_param("water_heights", result)
+	
+	# Calculate a new frame. First, get the data of the last frame and modify it accordingly
+	var image_data = result.get_data()
+	
+	# Set outstanding pixels
+	for position_and_depth in _positions_to_set:
+		var pos = position_and_depth[0]
+		var depth = position_and_depth[1]
+		
+		image_data.lock()
+		image_data.set_pixel(floor(pos.x * 512), floor(pos.y * 512), Color(depth, 0.0, 0.0, 0.0))
+		image_data.unlock()
+	
+	_positions_to_set.clear()
+	
+	# Create an ImageTexture for this new frame
+	var previous_frame = ImageTexture.new()
+	previous_frame.create_from_image(image_data)
+	
+	# Set the previous texture in the shader so that a new texture will be available next frame
+	$WaterHeights.set_previous_texture(previous_frame)
+	
+	# Debug output if needed
+	if output_debug_textures and _frame_number > first_output_frame:
+		image_data.save_png("res://debugframes/frame%s.png" % [_frame_number])
+	
+	_frame_number += 1

addons/interactive_water/Water.shader

@@ -0,0 +1,18 @@
+shader_type spatial;
+
+uniform sampler2D water_heights;
+
+
+float read_height(sampler2D tex, vec2 uv) {
+	return texture(tex, uv).r + texture(tex, uv).g / 255.0;
+}
+
+void fragment() {
+	ALBEDO = vec3(0.5, 0.7, 1.0) * (read_height(water_heights, UV) - 0.6) * 3.0;
+}
+
+void vertex() {
+	float vertex_distance = length(VERTEX) * 0.06;
+	
+	VERTEX += NORMAL * (read_height(water_heights, UV) * 40.0 - pow(2, vertex_distance));
+}

addons/interactive_water/Water.tscn

@@ -0,0 +1,38 @@
+[gd_scene load_steps=9 format=2]
+
+[ext_resource path="res://addons/interactive_water/Water.shader" type="Shader" id=1]
+[ext_resource path="res://addons/interactive_water/Water.gd" type="Script" id=3]
+[ext_resource path="res://addons/interactive_water/WaterUpdateMaterial.tres" type="Material" id=4]
+[ext_resource path="res://addons/interactive_water/PersistentShaderTexture.tscn" type="PackedScene" id=5]
+
+[sub_resource type="ViewportTexture" id=1]
+viewport_path = NodePath("WaterHeightViewport")
+
+[sub_resource type="ShaderMaterial" id=2]
+resource_local_to_scene = true
+shader = ExtResource( 1 )
+shader_param/water_heights = SubResource( 1 )
+
+[sub_resource type="PlaneMesh" id=3]
+subdivide_width = 512
+subdivide_depth = 512
+
+[sub_resource type="PlaneShape" id=4]
+
+[node name="Water" type="Spatial"]
+script = ExtResource( 3 )
+
+[node name="WaterMesh" type="MeshInstance" parent="."]
+material_override = SubResource( 2 )
+mesh = SubResource( 3 )
+material/0 = null
+
+[node name="StaticBody" type="StaticBody" parent="WaterMesh"]
+transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.6, 0 )
+
+[node name="CollisionShape" type="CollisionShape" parent="WaterMesh/StaticBody"]
+shape = SubResource( 4 )
+
+[node name="WaterHeights" parent="." instance=ExtResource( 5 )]
+size = Vector2( 512, 512 )
+shader_material = ExtResource( 4 )

addons/interactive_water/WaterHeights.gd

@@ -0,0 +1,30 @@
+extends Node
+
+# A texture which is continuously (statefully) updated by a shader.
+#
+# Typical usage: Retrieve the current result with `get_texture` and, at the end of the frame,
+# re-insert that texture (updated if needed) with `set_previous_texture`.
+#
+# Note that the given shader needs to accept a `previous_frame` sampler2D. This represents the
+# result of the last frame which is used for generating the new result.
+
+
+export var size := Vector2(64, 64)
+export var shader_material: ShaderMaterial
+
+
+func _ready():
+	$Viewport/Texture.rect_min_size = size
+	$Viewport/Texture.rect_size = size
+	$Viewport.size = size
+	
+	assert(shader_material)
+	$Viewport/Texture.material = shader_material
+
+
+func get_texture():
+	return $Viewport.get_texture()
+
+
+func set_previous_texture(texture):
+	$Viewport/Texture.material.set_shader_param("previous_frame", texture)

addons/interactive_water/WaterUpdate.shader

@@ -0,0 +1,63 @@
+shader_type canvas_item;
+render_mode unshaded, blend_disabled;
+
+uniform sampler2D previous_frame;
+
+uniform float water_height = 0.6;
+
+uniform float height_damping = 0.13;
+uniform float velocity_damping = 0.8;
+uniform float spread = 0.94;
+
+// Height and Velocity are encoded in two components each, so RG is height and BA is velocity.
+// This is needed to get a workable accuracy.
+float read_height(sampler2D tex, vec2 uv) {
+	return texture(tex, uv).r + texture(tex, uv).g / 255.0;
+}
+float read_velocity(sampler2D tex, vec2 uv) {
+	return texture(tex, uv).b + texture(tex, uv).a / 255.0;
+}
+float get_encoded_remainder(float num) {
+	return fract(num * 255.0);
+}
+
+void fragment() {
+	// Read values here
+	float height_here = read_height(previous_frame, UV);
+	float velocity_here = read_velocity(previous_frame, UV);
+	
+	// Apply force towards the base height
+	// This follows from the damped harmonic oscillator equation F = -kx-bv
+	float force = -height_damping * (height_here - water_height) - velocity_here * velocity_damping;
+	float acceleration_here = force;
+	
+	// In addition to each individual height behaving like a spring, neighbouring heights are
+	// "connected by springs" as well:
+	
+	// Read more samples
+	float uv_mod = 1.0 / float(textureSize(previous_frame, 0).x);
+	
+	float height_up = read_height(previous_frame, UV + vec2(0.0, uv_mod));
+	float height_down = read_height(previous_frame, UV + vec2(0.0, -uv_mod));
+	float height_left = read_height(previous_frame, UV + vec2(-uv_mod, 0.0));
+	float height_right = read_height(previous_frame, UV + vec2(uv_mod, 0.0));
+	
+	// Calculate differences
+	float up_delta = spread * (height_up - height_here);
+	float down_delta = spread * (height_down - height_here);
+	float left_delta = spread * (height_left - height_here);
+	float right_delta = spread * (height_right - height_here);
+	
+	// Use the biggest delta to apply to this height
+	float sum_delta = max(max(left_delta, right_delta), max(up_delta, down_delta));
+	
+	// Apply velocity and height
+	velocity_here += sum_delta + acceleration_here;
+	height_here += velocity_here;
+	
+	// Write to the texture
+	COLOR = vec4(
+		height_here, get_encoded_remainder(height_here),
+		velocity_here, get_encoded_remainder(velocity_here)
+	);
+}

addons/interactive_water/WaterUpdateMaterial.tres

@@ -0,0 +1,10 @@
+[gd_resource type="ShaderMaterial" load_steps=2 format=2]
+
+[ext_resource path="res://addons/interactive_water/WaterUpdate.shader" type="Shader" id=1]
+
+[resource]
+shader = ExtResource( 1 )
+shader_param/water_height = 0.6
+shader_param/height_damping = 0.13
+shader_param/velocity_damping = 0.8
+shader_param/spread = 0.94