Shader precompilation (without bug)

COGITO/Assets/Shader/ShaderLoader.tscn

@@ -0,0 +1,43 @@
+[gd_scene load_steps=6 format=3 uid="uid://b3bej4wl0tvj0"]
+
+[ext_resource type="Script" path="res://COGITO/Assets/Shader/ShaderPrecompiler.gd" id="1_5rykf"]
+
+[sub_resource type="QuadMesh" id="QuadMesh_8skhu"]
+size = Vector2(0, 0)
+
+[sub_resource type="ViewportTexture" id="ViewportTexture_dghy8"]
+viewport_path = NodePath("SubViewport")
+
+[sub_resource type="StandardMaterial3D" id="StandardMaterial3D_k37ri"]
+resource_local_to_scene = true
+albedo_texture = SubResource("ViewportTexture_dghy8")
+
+[sub_resource type="QuadMesh" id="QuadMesh_upqev"]
+
+[node name="ShaderCache" type="MeshInstance3D"]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, -1)
+mesh = SubResource("QuadMesh_8skhu")
+surface_material_override/0 = SubResource("StandardMaterial3D_k37ri")
+script = ExtResource("1_5rykf")
+
+[node name="SubViewport" type="SubViewport" parent="."]
+
+[node name="QuadRender" type="MeshInstance3D" parent="SubViewport"]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, -20, 0)
+layers = 262144
+mesh = SubResource("QuadMesh_upqev")
+skeleton = NodePath("../..")
+
+[node name="VisibleOnScreenNotifier3D" type="VisibleOnScreenNotifier3D" parent="SubViewport"]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, -20, 0)
+layers = 262144
+aabb = AABB(-0.5, 0, -1, 1, 1, 2)
+
+[node name="Camera3D" type="Camera3D" parent="SubViewport"]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, -20, 0)
+cull_mask = 262144
+current = true
+
+[connection signal="screen_entered" from="SubViewport/VisibleOnScreenNotifier3D" to="." method="_on_visible_on_screen_notifier_3d_screen_entered"]
+[connection signal="screen_exited" from="SubViewport/VisibleOnScreenNotifier3D" to="." method="_on_visible_on_screen_notifier_3d_screen_exited"]
+[connection signal="tree_exiting" from="SubViewport/VisibleOnScreenNotifier3D" to="." method="_on_visible_on_screen_notifier_3d_tree_exiting"]

COGITO/Assets/Shader/ShaderPrecompiler.gd

@@ -0,0 +1,47 @@
+extends Node3D
+class_name ShaderPrecompiler
+
+static var scene = preload("./ShaderLoader.tscn")
+static var shader_compiler_scene = null
+static var quad = null
+
+var materials : Array[ShaderMaterial]
+
+const placement = Vector3.ONE*9999
+const SHADER_LAYER = 19
+
+var is_rendering : bool = false # debugging
+static var queued = false
+
+# UNKNOWN: MultimeshInstances? Particles?
+static func precompile(tree : SceneTree, shader : ShaderMaterial):
+	if shader_compiler_scene == null:
+		shader_compiler_scene = scene.instantiate()
+		tree.root.get_camera_3d().add_child(shader_compiler_scene)
+		quad = shader_compiler_scene.get_node("./SubViewport/QuadRender")
+
+	shader_compiler_scene.materials.push_back(shader)
+	if not queued:
+		queued = true
+
+func _process(delta):
+	if not queued:
+		return
+	if len(shader_compiler_scene.materials) == 0:
+		queued = false
+		shader_compiler_scene.queue_free()
+	else:
+		var mat = shader_compiler_scene.materials.pop_back()
+		print(mat)
+		shader_compiler_scene.material_override = mat
+
+func _on_visible_on_screen_notifier_3d_screen_entered():
+	is_rendering = true
+
+func _on_visible_on_screen_notifier_3d_screen_exited():
+	is_rendering = false
+
+
+func _on_visible_on_screen_notifier_3d_tree_exiting():
+	if shader_compiler_scene == self:
+		shader_compiler_scene = null

COGITO/Assets/Shader/ShaderSpace.gd

@@ -10,6 +10,10 @@ class_name ShaderSpace
 ## If you're looking for viewmodel rendering, use ViewmodelSpace.gd
 ## @experimental
 
+## Godot's rendering engine will only compile a shader when it appears in the camera for the first time which can cause stutters.
+## This flag will force Godot to render all shaders when this space enters the scene.
+## If you have a lot of shaders, 
+@export var precompile_on_enter : bool = true
 var _bake : bool = false
 ## This will 'bake' the custom materials this script generates -- otherwise the materials are generated when this node enters the scene. 
 ## WARNING: Please note any changes you make to the *baked* versions of the Materials will not stay if/when you revert back to unbaked. 
@@ -119,10 +123,14 @@ func convert_surface(mat : Material):
 		if Engine.is_editor_hint() and not _bake:
 			# un-baking
 			return mat.get_original_material()
+		elif precompile_on_enter and not Engine.is_editor_hint():
+			ShaderPrecompiler.precompile(get_tree(),mat)
 		return mat
 	if not mat is StandardMaterial3D:
 		print("WARNING: Cannot convert ", mat, " to shader material")
 	else:
 		var newmaterial = Material3DConversion.convert_to_shadermat(mat,injected_vars,injected_vertex)
+		if precompile_on_enter and not Engine.is_editor_hint():
+			ShaderPrecompiler.precompile(get_tree(),newmaterial)
 		return newmaterial