some diffuse added for funzies

shaders/agent_shader.gdshader

@@ -1,8 +1,17 @@
 shader_type canvas_item;
 
+// Snippets of code drawn from https://gist.github.com/Bleuje/1e497df4505ca24c39ab3930a95700b3
+
 uniform sampler2D sim_texture;
 
-void fragment() {
+float gn(in vec2 coordinate, in float seed){
-	vec3 c = texture(sim_texture, UV).rgb;
+    return fract(tan(distance(coordinate*(seed+0.118446744073709551614), vec2(0.118446744073709551614, 0.314159265358979323846264)))*0.141421356237309504880169);
-	COLOR = vec4(c, 1.0);
+}
+
+void fragment() {
+	vec3 orig = texture(sim_texture, UV).rgb;
+	float agent = orig.r;
+	float trail = orig.g;
+	
+	COLOR = vec4(agent, trail, orig.b, 1.0);
 }

shaders/dissolve.gdshader

@@ -5,7 +5,16 @@ uniform sampler2D sim_texture;
 uniform float decay_factor;
 
 void fragment() {
-	float c = texture(sim_texture, UV).r;
+	vec3 orig = texture(sim_texture, UV).rgb;
-	c = c * decay_factor;
+	float trail = texture(sim_texture, UV).g;
-	COLOR = vec4(c, c, c, 1.0);
+
+	float sum = 0.0;
+	for(int i=-1;i<=1;i++) {
+		for(int j=-1;j<=1;j++) {
+			sum += texture(sim_texture, UV).g;
+		}
+	}
+	trail = sum / 9.0;
+	trail = trail * decay_factor;
+	COLOR = vec4(orig.r, trail, orig.b, 1.0);
 }

slime_simulation.gd

@@ -12,8 +12,8 @@ extends Node2D
 @onready var trail_shader: ShaderMaterial = $SubViewport2/Pass.material
 
 const MAX_TEXTURES: int = 2
-var next_texture: int = 0
+var _next_texture: int = 0
-var frame_count: int = 0
+var _frame_count: int = 0
 
 
 func _ready():
@@ -21,12 +21,12 @@ func _ready():
 
 
 func _process(_delta: float) -> void:
-	next_texture = (next_texture + 1) % MAX_TEXTURES
+	_next_texture = (_next_texture + 1) % MAX_TEXTURES
 	RenderingServer.call_on_render_thread(
-		_render_process.bind(next_texture, frame_count, decay_factor)
+		_render_process.bind(_next_texture, _frame_count, decay_factor)
 	)
 
-	frame_count = frame_count + 1
+	_frame_count = _frame_count + 1
 
 
 # Below is for rendering
@@ -42,14 +42,14 @@ func _create_initial_sim_texture(width: int, height: int) -> ImageTexture:
 	return sim_texture
 
 
-func _initialize_render(width: int, height: int) -> void:
+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:
+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())
 

slime_simulation.tscn

@@ -32,7 +32,7 @@ size = Vector2(1920, 1080)
 [sub_resource type="ShaderMaterial" id="ShaderMaterial_g2c28"]
 shader = ExtResource("3_s6nlv")
 shader_parameter/sim_texture = SubResource("Texture2DRD_s6nlv")
-shader_parameter/decay_factor = 0.95
+shader_parameter/decay_factor = 0.99
 
 [node name="SlimeSimulation" type="Node2D"]
 script = ExtResource("1_s6nlv")