Add //!steps directive, some code cleanup, updated README & examples

README.md

@@ -22,7 +22,7 @@ Just load an image using `//!load`, edit the shader code and hit `F5` to see the
 //!load <filepath>
 ```
 
-The image file will be read and available as the `TEXTURE` variable.
+The main image file will be read and available as the sampler2D `TEXTURE`.
 
 #### Load additional images
 
@@ -34,6 +34,28 @@ uniform sampler2D <name>;
 
 Have a look at the `place_texture.gdshader` example.
 
+### Have multiple steps with `//!steps n`
+
+You can apply your shaderfile multiple times. At every additional step, `TEXTURE` is the result of the previous step. This can be used to chain effects that cannot be easily chained otherwise.
+
+To query the current step index, a `STEP` uniform is automatically injected. If `steps` is set to `0`, your shader won't be applied at all.
+
+Example:
+
+```glsl
+//!load ...
+//!steps 5
+
+void fragment() {
+  if (STEP == 0) {
+    ...
+  } else if (STEP == 1) {
+    ...
+  }
+  // ... and so on
+}
+```
+
 ## Shaderlib
 
 This repo comes with a (still small) shader library including pre-written functions and more.  

examples/rgb_uv_distort.gdshader

@@ -1,13 +1,20 @@
 shader_type canvas_item;
 
+//!steps 9
 //!load ./swamp.jpg
 
-const float strength = 0.1;
+const float strength = 0.01;
 
 void fragment() {
+	float v;
+	if (STEP % 3 == 0) {
+		v = COLOR.r; // 3 times
+	} else if (STEP % 3 == 0) {
+		v = COLOR.g; // 3 times
+	} else {
+		v = COLOR.b; // 3 times
+	}
 	vec2 uv = UV;
-	float b = (COLOR.r + COLOR.g + COLOR.b) / 3.0;
-	uv.x = mix(uv.x, b, strength);
-	uv.y = mix(uv.y, b, strength);
+	uv.y -= v * strength;
 	COLOR = texture(TEXTURE, uv);
 }

scenes/main.tscn

@@ -42,7 +42,7 @@ script = ExtResource("8_mls06")
 [node name="EditorWindow" type="Window" parent="."]
 unique_name_in_owner = true
 disable_3d = true
-position = Vector2i(48, 80)
+position = Vector2i(48, 36)
 size = Vector2i(704, 704)
 script = ExtResource("6_8k0ha")
 

src/Compositor.gd

@@ -4,15 +4,10 @@ extends SubViewport
 @onready var image_sprite = %ImageSprite
 @onready var image_viewport_display = %ImageViewportDisplay
 
-var _fragment_function_regex: RegEx
+var _fragment_function_regex: RegEx = RegEx.create_from_string(r'\s*void\s+fragment\s*\(\s*\)\s*{\s*')
 
-func _init():
-	_fragment_function_regex = RegEx.new()
-	_fragment_function_regex.compile(r'\s*void\s+fragment\s*\(\s*\)\s*{\s*')
-
-func validate_shader_compilation() -> bool:
+func validate_shader_compilation(shader: Shader) -> bool:
 	# Inject code to validate shader compilation
-	var shader: Shader = Filesystem.shader.duplicate()
 	var shader_code = shader.code;
 	# -> get position of fragment shader
 	var fragment_function_match = _fragment_function_regex.search(shader.code)
@@ -29,19 +24,28 @@ func validate_shader_compilation() -> bool:
 	# test if uniform list is empty -> if it is empty, the shader compilation failed
 	return len(shader.get_shader_uniform_list()) > 0
 
+func inject_step_uniform(shader_code: String) -> Shader:
+	var shader = Shader.new()
+	# this should run after validate_shader_compilation()
+	var fragment_function_match = _fragment_function_regex.search(shader_code)
+	shader.code = shader_code.insert(fragment_function_match.get_start(), "\nuniform int STEP;")
+	return shader
+
 func update() -> Array: # returns error messages (strings)
-	if not validate_shader_compilation():
+	# inject STEP uniform & get number of steps
+	var shader: Shader = inject_step_uniform(Filesystem.shader_code)
+	var step: int = ShaderDirectiveParser.parse_steps_directive(shader)
+	# validate shader
+	if not validate_shader_compilation(shader):
 		return ["Shader compilation failed!"]
 	var errors = []
-	var fit_image = false
-	# load texture(s)
-	Filesystem.clear_additional_images()
-	# ... from //!load directive -> TEXTURE
-	var m = ShaderDirectiveParser.parse_load_directive(Filesystem.shader)
+	# load texture(s) from //!load directive -> TEXTURE
+	var m = ShaderDirectiveParser.parse_load_directive(shader)
 	if len(m) < 1:
 		errors.append("Didn't find a load directive!")
 		return errors
 	var original_image_path = Filesystem.get_absolute_path(m[1])
+	var fit_image = false
 	if original_image_path != Filesystem.last_original_image_path:
 		fit_image = true
 	var err = Filesystem.load_original_image(original_image_path)
@@ -50,7 +54,8 @@ func update() -> Array: # returns error messages (strings)
 		image_viewport_display.hide()
 		return errors
 	# ... from //!load+ directives
-	for n in ShaderDirectiveParser.parse_load_additional_directive(Filesystem.shader):
+	Filesystem.clear_additional_images()
+	for n in ShaderDirectiveParser.parse_load_additional_directive(shader):
 		err = Filesystem.load_additional_image(n[1], Filesystem.get_absolute_path(n[2]))
 		if err != "":
 			errors.append(err)
@@ -60,22 +65,27 @@ func update() -> Array: # returns error messages (strings)
 	image_sprite.texture = Filesystem.original_image
 	image_sprite.offset = Filesystem.original_image.get_size() / 2
 	self.size = Filesystem.original_image.get_size()
+	# create shader material
 	var mat = ShaderMaterial.new()
-	mat.shader = Filesystem.shader
-	# ... as shader parameters
+	mat.shader = shader
+	# add images as shader parameters
 	for key in Filesystem.additional_images:
 		mat.set_shader_parameter(
 			key, # uniform param name
 			Filesystem.additional_images[key])
-	# assign material
-	image_sprite.material = mat
-	# Get viewport texture
-	await RenderingServer.frame_post_draw # for good measure
-	Filesystem.result = get_texture().get_image()
-	image_sprite.material = null
-	image_sprite.texture = ImageTexture.create_from_image(Filesystem.result)
-	if fit_image:
-		camera.fit_image()
+	# iterate n times
+	for i in range(step):
+		# set STEP param
+		mat.set_shader_parameter("STEP", i)
+		# assign material
+		image_sprite.material = mat
+		# Get viewport texture
+		await RenderingServer.frame_post_draw # for good measure
+		Filesystem.result = get_texture().get_image()
+		image_sprite.material = null
+		image_sprite.texture = ImageTexture.create_from_image(Filesystem.result)
+		if fit_image:
+			camera.fit_image()
 	camera.update_vd_zoomlevel()
 	image_viewport_display.show()
 	# done

src/Editor.gd

@@ -208,7 +208,7 @@ func _input(event):
 		_on_save_shader_button_pressed()
 
 func update_code_edit():
-	code_editor.text = Filesystem.shader.code
+	code_editor.text = Filesystem.shader_code
 
 enum Status {OKAY, ERROR, UNKNOWN = -1}
 
@@ -239,14 +239,14 @@ func _on_open_shader_button_pressed():
 	open_shader_dialog.show()
 
 func _on_save_shader_button_pressed():
-	Filesystem.shader.code = code_editor.text
+	Filesystem.shader_code = code_editor.text
 	if Filesystem.last_shader_savepath == "":
 		_on_save_shader_as_button_pressed()
 	else:
 		_on_save_shader_dialog_file_selected(Filesystem.last_shader_savepath)
 
 func _on_save_shader_as_button_pressed() -> void:
-	Filesystem.shader.code = code_editor.text
+	Filesystem.shader_code = code_editor.text
 	if Filesystem.last_shader_savepath == "":
 		save_shader_dialog.current_file = "filter.gdshader"
 	else:
@@ -257,7 +257,7 @@ func _on_fit_image_button_pressed():
 	camera.fit_image()
 
 func _on_apply_shader_button_pressed():
-	Filesystem.shader.code = code_editor.text
+	Filesystem.shader_code = code_editor.text
 	var errors = await compositor.update()
 	if len(errors) > 0:
 		update_status(Status.ERROR, "\n".join(errors))

src/Filesystem.gd

@@ -1,7 +1,7 @@
 extends Node
 
 @onready var template_shader: Shader = load("res://src/shader/template.gdshader")
-@onready var shader: Shader = template_shader.duplicate()
+@onready var shader_code: String = template_shader.code
 
 var original_image: ImageTexture
 var additional_images: Dictionary
@@ -13,7 +13,7 @@ var last_shader_savepath = ""
 var last_original_image_path = ""
 
 func reset():
-	self.shader = self.template_shader.duplicate()
+	self.shader_code = self.template_shader.code
 	self.last_image_savepath = ""
 	self.last_shader_savepath = ""
 	self.last_original_image_path = ""
@@ -61,9 +61,7 @@ func save_result(path: String):
 func load_shader(path: String):
 	print("Load ", path)
 	var file = FileAccess.open(path, FileAccess.READ)
-	var shader_code = file.get_as_text()
-	self.shader = Shader.new()
-	shader.code = shader_code
+	self.shader_code = file.get_as_text()
 	if "/" in path: # update current working directory
 		self.cwd = path.substr(0, path.rfind("/"))
 	self.last_shader_savepath = path
@@ -71,7 +69,7 @@ func load_shader(path: String):
 func save_shader(path: String):
 	print("Save ", path)
 	var file = FileAccess.open(path, FileAccess.WRITE)
-	file.store_string(self.shader.code)
+	file.store_string(self.shader_code)
 	if "/" in path: # update current working directory
 		self.cwd = path.substr(0, path.rfind("/"))
 	self.last_shader_savepath = path

src/ShaderDirectiveParser.gd

@@ -1,16 +1,11 @@
 extends Node
 
-var _load_regex: RegEx
-var _load_additional_regex: RegEx
-
-func _ready():
-	self._load_regex = RegEx.new()
-	self._load_additional_regex = RegEx.new()
-	self._load_regex.compile(r'\/\/!load\s(.*)')
-	self._load_additional_regex.compile(r'\/\/!load\+\s(\w*)\s(.*)')
+var _load_regex: RegEx = RegEx.create_from_string(r'\/\/!load\s(.*)')
+var _load_additional_regex: RegEx = RegEx.create_from_string(r'\/\/!load\+\s(\w*)\s(.*)')
+var _iterate_regex: RegEx = RegEx.create_from_string(r'\/\/!steps\s([0-9]+)\s*')
 
 func parse_load_directive(shader: Shader) -> PackedStringArray:
-	var regex_match = self._load_regex.search(Filesystem.shader.code)
+	var regex_match = self._load_regex.search(shader.code)
 	if regex_match == null:
 		return []
 	return regex_match.strings
@@ -20,3 +15,10 @@ func parse_load_additional_directive(shader: Shader) -> Array[PackedStringArray]
 	for m in self._load_additional_regex.search_all(shader.code):
 		results.append(m.strings)
 	return results
+
+func parse_steps_directive(shader: Shader) -> int:
+	var regex_match = self._iterate_regex.search(shader.code)
+	if regex_match == null:
+		return 1
+	else:
+		return max(0, int(regex_match.strings[1]))