initial setup

project.godot

@@ -30,4 +30,6 @@ folder_colors={
 
 [rendering]
 
+renderer/rendering_method="gl_compatibility"
+renderer/rendering_method.mobile="gl_compatibility"
 environment/defaults/default_clear_color=Color(0.0605303, 0.0605304, 0.0605303, 1)

shaders/agent_shader.gdshader

@@ -0,0 +1,8 @@
+shader_type canvas_item;
+
+uniform sampler2D sim_texture;
+
+void fragment() {
+	vec3 c = texture(sim_texture, UV).rgb;
+	COLOR = vec4(c, 1.0);
+}

shaders/dissolve.gdshader

@@ -0,0 +1,11 @@
+shader_type canvas_item;
+
+uniform sampler2D sim_texture;
+
+uniform float decay_factor;
+
+void fragment() {
+	float c = texture(sim_texture, UV).r;
+	c = c * decay_factor;
+	COLOR = vec4(c, c, c, 1.0);
+}

shaders/dissolve.gdshader.uid

@@ -0,0 +1 @@
+uid://bj3v35wyy32la

shaders/trail_shader.gdshader

@@ -1,8 +0,0 @@
-shader_type canvas_item;
-
-void fragment() {
-	vec3 c1 = vec3(0.0, 0.4, 0.4);
-	vec3 c2 = vec3(0.4, 0.0, 0.4);
-	vec3 cout = mix(c1, c2, UV.x);
-	COLOR = vec4(cout, 1.0);
-}

shaders/view_simulation.gdshader

@@ -1,6 +1,6 @@
 shader_type canvas_item;
 
-uniform sampler2D view_texture;
+uniform sampler2D sim_texture;
 
 void fragment() {
 	vec3 v = texture(view_texture, UV).rgb;

slime_simulation.gd

@@ -1,12 +1,58 @@
 extends Node2D
 
-@onready var view := $View
-@onready var trail_shader: ShaderMaterial = $SubViewport/Pass1.material
+@export var render_width: int = 1920
+@export var render_height: int = 1080
+
+@export var decay_factor: float = 0.95
+
+@onready var view := $View
+@onready var pass_viewport := $SubViewport
+@onready var pass2_viewport := $SubViewport2
+@onready var agent_shader: ShaderMaterial = $SubViewport/Pass.material
+@onready var trail_shader: ShaderMaterial = $SubViewport2/Pass.material
+
+const MAX_TEXTURES: int = 2
+var next_texture: int = 0
+var frame_count: int = 0
 
-var view_texture: Texture2DRD = null
 
 func _ready():
-	pass
+	RenderingServer.call_on_render_thread(_initialize_render.bind(render_width, render_height))
+
 
 func _process(_delta: float) -> void:
-	pass
+	next_texture = (next_texture + 1) % MAX_TEXTURES
+	RenderingServer.call_on_render_thread(
+		_render_process.bind(next_texture, frame_count, decay_factor)
+	)
+
+	frame_count = frame_count + 1
+
+
+# Below is for rendering
+
+var rd: RenderingDevice = null
+var sim_texture: Texture2D = null
+
+
+func _create_initial_sim_texture(width: int, height: int) -> ImageTexture:
+	var sim_image := Image.create_empty(width, height, false, Image.FORMAT_RGBF)
+	sim_texture = ImageTexture.create_from_image(sim_image)
+
+	return sim_texture
+
+
+func _initialize_render(width: int, height: int) -> void:
+	rd = RenderingServer.get_rendering_device()
+
+	trail_shader.set_shader_parameter("sim_texture", pass_viewport.get_texture().get_rid())
+	trail_shader.set_shader_parameter("decay_factor", decay_factor)
+
+
+func _render_process(next_texture: int, frame_count: int, decay_factor: float) -> void:
+	if frame_count > 0:
+		agent_shader.set_shader_parameter("sim_texture", pass2_viewport.get_texture().get_rid())
+
+	trail_shader.set_shader_parameter("decay_factor", decay_factor)
+	trail_shader.set_shader_parameter("sim_texture", pass_viewport.get_texture().get_rid())
+	# agent_shader.set_shader_parameter("sim_texture", pass2_viewport.get_texture().get_rid())

slime_simulation.tscn

@@ -1,20 +1,39 @@
-[gd_scene load_steps=7 format=3 uid="uid://0q5qa7yiya83"]
+[gd_scene load_steps=12 format=3 uid="uid://0q5qa7yiya83"]
 
 [ext_resource type="Script" uid="uid://c6et88s5hp5c7" path="res://slime_simulation.gd" id="1_s6nlv"]
-[ext_resource type="Shader" uid="uid://cwt4a55lblykn" path="res://shaders/trail_shader.gdshader" id="3_vkm4v"]
+[ext_resource type="Shader" uid="uid://cwt4a55lblykn" path="res://shaders/agent_shader.gdshader" id="2_pxe3a"]
+[ext_resource type="Shader" uid="uid://bj3v35wyy32la" path="res://shaders/dissolve.gdshader" id="3_s6nlv"]
 
 [sub_resource type="QuadMesh" id="QuadMesh_h0wwo"]
 size = Vector2(1920, 1080)
 
 [sub_resource type="ViewportTexture" id="ViewportTexture_s6nlv"]
-viewport_path = NodePath("SubViewport")
+viewport_path = NodePath("SubViewport2")
+
+[sub_resource type="FastNoiseLite" id="FastNoiseLite_s6nlv"]
+offset = Vector3(97.54, 0, 0)
+fractal_octaves = 2
+
+[sub_resource type="NoiseTexture2D" id="NoiseTexture2D_g2c28"]
+width = 1920
+height = 1080
+generate_mipmaps = false
+noise = SubResource("FastNoiseLite_s6nlv")
 
 [sub_resource type="ShaderMaterial" id="ShaderMaterial_evymn"]
-shader = ExtResource("3_vkm4v")
+shader = ExtResource("2_pxe3a")
+shader_parameter/sim_texture = SubResource("NoiseTexture2D_g2c28")
 
 [sub_resource type="QuadMesh" id="QuadMesh_s6nlv"]
 size = Vector2(1920, 1080)
 
+[sub_resource type="Texture2DRD" id="Texture2DRD_s6nlv"]
+
+[sub_resource type="ShaderMaterial" id="ShaderMaterial_g2c28"]
+shader = ExtResource("3_s6nlv")
+shader_parameter/sim_texture = SubResource("Texture2DRD_s6nlv")
+shader_parameter/decay_factor = 0.95
+
 [node name="SlimeSimulation" type="Node2D"]
 script = ExtResource("1_s6nlv")
 
@@ -24,13 +43,27 @@ mesh = SubResource("QuadMesh_h0wwo")
 texture = SubResource("ViewportTexture_s6nlv")
 
 [node name="SubViewport" type="SubViewport" parent="."]
+disable_3d = true
 transparent_bg = true
 handle_input_locally = false
 snap_2d_vertices_to_pixel = true
 size = Vector2i(1920, 1080)
 render_target_update_mode = 4
 
-[node name="Pass1" type="MeshInstance2D" parent="SubViewport"]
+[node name="Pass" type="MeshInstance2D" parent="SubViewport"]
 material = SubResource("ShaderMaterial_evymn")
 position = Vector2(960, 540)
 mesh = SubResource("QuadMesh_s6nlv")
+
+[node name="SubViewport2" type="SubViewport" parent="."]
+disable_3d = true
+transparent_bg = true
+handle_input_locally = false
+snap_2d_vertices_to_pixel = true
+size = Vector2i(1920, 1080)
+render_target_update_mode = 4
+
+[node name="Pass" type="MeshInstance2D" parent="SubViewport2"]
+material = SubResource("ShaderMaterial_g2c28")
+position = Vector2(960, 540)
+mesh = SubResource("QuadMesh_s6nlv")

slime_simulation_cs/show_simulation_cs.gdshader

@@ -1,4 +1,5 @@
 shader_type canvas_item;
+
 uniform sampler2D trail_tex;
 
 void fragment() {