diff --git a/addons/material_maker/engine/gen_base.gd b/addons/material_maker/engine/gen_base.gd
index e665262..72a5503 100644
--- a/addons/material_maker/engine/gen_base.gd
+++ b/addons/material_maker/engine/gen_base.gd
@@ -110,12 +110,19 @@ func get_parameter_def(param_name : String) -> Dictionary:
 	return {}
 
 func get_parameter(n : String):
-	return parameters[n]
+	if parameters.has(n):
+		return parameters[n]
+	else:
+		return get_parameter_def(n).default
 
 func set_parameter(n : String, v) -> void:
 	parameters[n] = v
 	source_changed(0)
 	emit_signal("parameter_changed", n, v)
+	if is_inside_tree():
+		var parameter_def : Dictionary = get_parameter_def(n)
+		if parameter_def.has("type") and parameter_def.type == "float":
+			get_tree().call_group("preview", "on_float_parameter_changed", "p_o%s_%s" % [ str(get_instance_id()), n ], v)
 
 func notify_output_change(output_index : int) -> void:
 	var targets = get_targets(output_index)
@@ -159,7 +166,7 @@ func get_input_shader(input_index : int) -> Dictionary:
 func get_shader(output_index : int, context) -> Dictionary:
 	return get_shader_code("UV", output_index, context)
 
-func generate_preview_shader(src_code, type) -> String:
+static func generate_preview_shader(src_code, type, main_fct = "void fragment() { COLOR = preview_2d(UV); }") -> String:
 	var code
 	code = "shader_type canvas_item;\n"
 	code += "render_mode blend_disabled;\n"
@@ -182,6 +189,7 @@ func generate_preview_shader(src_code, type) -> String:
 		shader_code += preview_code
 	#print("GENERATED SHADER:\n"+shader_code)
 	code += shader_code
+	code += main_fct
 	return code
 
 func render(output_index : int, size : int, preview : bool = false) -> Object:
diff --git a/addons/material_maker/engine/gen_shader.gd b/addons/material_maker/engine/gen_shader.gd
index 35c866b..a93e384 100644
--- a/addons/material_maker/engine/gen_shader.gd
+++ b/addons/material_maker/engine/gen_shader.gd
@@ -188,7 +188,7 @@ func subst(string : String, context : MMGenContext, uv : String = "") -> Diction
 			var value = parameters[p.name]
 			var value_string = null
 			if p.type == "float":
-				value_string = "%.9f" % value
+				value_string = "p_%s_%s" % [ genname, p.name ]
 			elif p.type == "size":
 				value_string = "%.9f" % pow(2, value)
 			elif p.type == "enum":
@@ -247,7 +247,9 @@ func _get_shader_code(uv : String, output_index : int, context : MMGenContext) -
 		if !context.has_variant(self):
 			# Generate functions for gradients
 			for p in shader_model.parameters:
-				if p.type == "gradient":
+				if p.type == "float":
+					rv.defs += "uniform float p_%s_%s = %.9f;\n" % [ genname, p.name, parameters[p.name] ]
+				elif p.type == "gradient":
 					var g = parameters[p.name]
 					if !(g is MMGradient):
 						g = MMGradient.new()
diff --git a/addons/material_maker/engine/gen_switch.gd b/addons/material_maker/engine/gen_switch.gd
index d17e246..2dce86d 100644
--- a/addons/material_maker/engine/gen_switch.gd
+++ b/addons/material_maker/engine/gen_switch.gd
@@ -39,7 +39,7 @@ func get_input_defs() -> Array:
 
 func get_output_defs() -> Array:
 	var rv : Array = []
-	for o in range(parameters.outputs):
+	for o in range(get_parameter("outputs")):
 		var n = PoolByteArray([65+o]).get_string_from_ascii()
 		rv.push_back({ name=n, type="any" })
 	return rv
diff --git a/addons/material_maker/nodes/preview_f.shader b/addons/material_maker/nodes/preview_f.shader
index fc4f1d5..5f9a087 100644
--- a/addons/material_maker/nodes/preview_f.shader
+++ b/addons/material_maker/nodes/preview_f.shader
@@ -1,5 +1,4 @@
-void fragment() {
-	vec2 uv = UV;
+vec4 preview_2d(vec2 uv) {
 	$(code)
-	COLOR = vec4(vec3($(value)), 1.0);
+	return vec4(vec3($(value)), 1.0);
 }
diff --git a/addons/material_maker/nodes/preview_rgb.shader b/addons/material_maker/nodes/preview_rgb.shader
index 416d73e..7c08ec1 100644
--- a/addons/material_maker/nodes/preview_rgb.shader
+++ b/addons/material_maker/nodes/preview_rgb.shader
@@ -1,5 +1,4 @@
-void fragment() {
-	vec2 uv = UV;
+vec4 preview_2d(vec2 uv) {
 	$(code)
-	COLOR = vec4($(value), 1.0);
+	return vec4($(value), 1.0);
 }
diff --git a/addons/material_maker/nodes/preview_rgba.shader b/addons/material_maker/nodes/preview_rgba.shader
index be33b4b..f624707 100644
--- a/addons/material_maker/nodes/preview_rgba.shader
+++ b/addons/material_maker/nodes/preview_rgba.shader
@@ -1,5 +1,4 @@
-void fragment() {
-	vec2 uv = UV;
+vec4 preview_2d(vec2 uv) {
 	$(code)
-	COLOR = $(value);
+	return $(value);
 }
diff --git a/addons/material_maker/nodes/preview_sdf2d.shader b/addons/material_maker/nodes/preview_sdf2d.shader
index 33bbb32..9a3f852 100644
--- a/addons/material_maker/nodes/preview_sdf2d.shader
+++ b/addons/material_maker/nodes/preview_sdf2d.shader
@@ -1,10 +1,9 @@
-void fragment() {
-	vec2 uv = UV;
+vec4 preview_2d(vec2 uv) {
 	$(code)
 	float d = $(value);
 	vec3 col = vec3(cos(d*min(256, preview_size)));
 	col *= clamp(1.0-d*d, 0.0, 1.0);
 	col *= vec3(1.0, vec2(step(-0.015, d)));
 	col *= vec3(vec2(step(d, 0.015)), 1.0);
-	COLOR = vec4(col, 1.0);
+	return vec4(col, 1.0);
 }
diff --git a/addons/material_maker/nodes/preview_sdf3d.shader b/addons/material_maker/nodes/preview_sdf3d.shader
index 25d87c6..ca95ab8 100644
--- a/addons/material_maker/nodes/preview_sdf3d.shader
+++ b/addons/material_maker/nodes/preview_sdf3d.shader
@@ -20,8 +20,8 @@ vec3 normal(vec3 p) {
     return normalize(n);
 }
 
-void fragment() {
-	vec2 uv = UV-vec2(0.5);
+vec4 preview_2d(vec2 uv) {
+	uv -= vec2(0.5);
 	vec3 p = vec3(uv, 2.0-raymarch(vec3(uv, 2.0), vec3(0.0, 0.0, -1.0)));
 	vec3 n = normal(p);
 	vec3 l = vec3(5.0, 5.0, 10.0);
@@ -29,5 +29,5 @@ void fragment() {
 	float o = step(p.z, 0.001);
 	float shadow = 1.0-0.75*step(raymarch(l, -ld), length(l-p)-0.01);
 	float light = 0.3+0.7*dot(n, ld)*shadow;
-	COLOR = vec4(vec3(0.8+0.2*o, 0.8+0.2*o, 1.0)*light, 1.0);
+	return vec4(vec3(0.8+0.2*o, 0.8+0.2*o, 1.0)*light, 1.0);
 }
diff --git a/addons/material_maker/nodes/preview_sdf3dc.shader b/addons/material_maker/nodes/preview_sdf3dc.shader
index 7c6ebbe..246d536 100644
--- a/addons/material_maker/nodes/preview_sdf3dc.shader
+++ b/addons/material_maker/nodes/preview_sdf3dc.shader
@@ -31,8 +31,8 @@ vec3 rm_color(float c) {
 	return 1.0 * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), 1.0);
 }
 
-void fragment() {
-	vec2 uv = UV-vec2(0.5);
+vec4 preview_2d(vec2 uv) {
+	uv -= vec2(0.5);
 	vec2 rm = raymarch(vec3(uv, 2.0), vec3(0.0, 0.0, -1.0));
 	vec3 p = vec3(uv, 2.0-rm.x);
 	vec3 n = normal(p);
@@ -41,5 +41,5 @@ void fragment() {
 	float o = step(p.z, 0.001);
 	float shadow = 1.0-0.75*step(raymarch(l, -ld).x, length(l-p)-0.01);
 	float light = 0.3+0.7*dot(n, ld)*shadow;
-	COLOR = vec4(mix(rm_color(fract(rm.y)), vec3(0.9), o)*light, 1.0);
+	return vec4(mix(rm_color(fract(rm.y)), vec3(0.9), o)*light, 1.0);
 }
diff --git a/addons/material_maker/nodes/preview_tex3d.shader b/addons/material_maker/nodes/preview_tex3d.shader
index 1151e89..552e505 100644
--- a/addons/material_maker/nodes/preview_tex3d.shader
+++ b/addons/material_maker/nodes/preview_tex3d.shader
@@ -24,8 +24,8 @@ vec3 normal(vec3 p) {
     return normalize(n);
 }
 
-void fragment() {
-    vec2 uv = UV-vec2(0.5);
+vec4 preview_2d(vec2 uv) {
+    vec2 uv -= vec2(0.5);
     vec3 p = vec3(uv, 2.0-raymarch(vec3(uv, 2.0), vec3(0.0, 0.0, -1.0)));
     vec3 n = normal(p);
     vec3 l = vec3(5.0, 5.0, 10.0);
@@ -33,5 +33,5 @@ void fragment() {
     float o = step(p.z, 0.001);
     float shadow = 1.0-0.75*step(raymarch(l, -ld), length(l-p)-0.01);
     float light = 0.3+0.7*dot(n, ld)*shadow;
-    COLOR = vec4(calcColor(vec4(p, 0.0))*light, 1.0);
+    return vec4(calcColor(vec4(p, 0.0))*light, 1.0);
 }
diff --git a/material_maker/main_window.gd b/material_maker/main_window.gd
index 7700f3e..48f236a 100644
--- a/material_maker/main_window.gd
+++ b/material_maker/main_window.gd
@@ -583,33 +583,33 @@ func update_preview_2d(node = null) -> void:
 					node = n
 					break
 		if node != null:
-			var result = node.generator.render(0, 1024, true)
-			while result is GDScriptFunctionState:
-				result = yield(result, "completed")
-			var tex = ImageTexture.new()
-			result.copy_to_texture(tex)
-			result.release()
-			preview_2d.set_preview_texture(tex)
-			preview_2d_background.set_preview_texture(tex)
+			preview_2d.set_generator(node.generator)
+			preview_2d_background.set_generator(node.generator)
 		else:
-			preview_2d.set_preview_texture(null)
-			preview_2d_background.set_preview_texture(null)
+			preview_2d.set_generator(null)
+			preview_2d_background.set_generator(null)
 
 func update_preview_3d(previews : Array) -> void:
+	var visible_previews = []
+	for p in previews:
+		if p.is_visible_in_tree():
+			visible_previews.push_back(p)
+	if visible_previews.empty():
+		return
 	var graph_edit : MMGraphEdit = get_current_graph_edit()
 	if graph_edit != null and graph_edit.top_generator != null and graph_edit.top_generator.has_node("Material"):
 		var gen_material = graph_edit.top_generator.get_node("Material")
 		var status = gen_material.render_textures()
 		while status is GDScriptFunctionState:
 			status = yield(status, "completed")
-		for p in previews:
+		for p in visible_previews:
 			gen_material.update_materials(p.get_materials())
 
 var selected_node = null
 func on_selected_node_change(node) -> void:
 	if node != selected_node:
 		selected_node = node
-		preview_2d.setup_controls(node.generator if node != null else null)
+		preview_2d.set_generator(node.generator if node != null else null)
 		update_preview_2d(node)
 
 func _on_Projects_tab_changed(tab) -> void:
diff --git a/material_maker/preview/preview_2d.gd b/material_maker/preview/preview_2d.gd
index bfcd9f3..46e29a3 100644
--- a/material_maker/preview/preview_2d.gd
+++ b/material_maker/preview/preview_2d.gd
@@ -1,24 +1,39 @@
 extends ColorRect
 
-var generator = null
+export(String, MULTILINE) var shader : String = ""
 
-func set_preview_texture(tex: Texture) -> void:
-	material.set_shader_param("tex", tex)
+var generator : MMGenBase = null
 
-func on_resized() -> void:
-	material.set_shader_param("size", rect_size)
-	setup_controls(generator)
-
-func setup_controls(g : MMGenBase) -> void:
+func set_generator(g : MMGenBase) -> void:
+	if generator != null and is_instance_valid(generator):
+		generator.disconnect("float_param_changed", self, "on_float_param_changed")
+	var source = { defs="", code="", textures={}, type="f", f="1.0" }
 	if is_instance_valid(g):
 		generator = g
 		var param_defs : Array = generator.get_parameter_defs()
 		for c in get_children():
 			c.setup_control(generator, param_defs)
+		generator.connect("float_param_changed", self, "on_float_param_changed")
+		var gen_output_defs = generator.get_output_defs()
+		if ! gen_output_defs.empty():
+			var context : MMGenContext = MMGenContext.new()
+			source = generator.get_shader_code("uv", 0, context)
+			while source is GDScriptFunctionState:
+				source = yield(source, "completed")
+			if source.empty():
+				source = { defs="", code="", textures={}, type="f", f="1.0" }
 	else:
 		g = null
 		for c in get_children():
 			c.setup_control(generator, [])
+	material.shader.code = MMGenBase.generate_preview_shader(source, source.type, shader)
+
+func on_float_parameter_changed(n : String, v : float) -> void:
+	material.set_shader_param(n, v)
+
+func on_resized() -> void:
+	material.set_shader_param("size", rect_size)
+	set_generator(generator)
 
 func value_to_pos(value : Vector2) -> Vector2:
 	return rect_size*0.5+value*min(rect_size.x, rect_size.y)/1.2
diff --git a/material_maker/preview/preview_2d.tscn b/material_maker/preview/preview_2d.tscn
index 4bcc1f4..6fb149a 100644
--- a/material_maker/preview/preview_2d.tscn
+++ b/material_maker/preview/preview_2d.tscn
@@ -3,28 +3,14 @@
 [ext_resource path="res://material_maker/preview/preview_2d.gd" type="Script" id=1]
 
 [sub_resource type="Shader" id=1]
-code = "shader_type canvas_item;
-
-uniform sampler2D tex;
-uniform vec2 size;
-
-void fragment() {
-	float ms = max(size.x, size.y);
-	vec2 uv = fract(0.5+1.2*(UV-vec2(0.5))*ms/size.yx);
-	float is = min(size.x, size.y)/1.2;
-	vec2 m2 = min(fract(uv), 1.0-fract(uv));
-	vec4 image = texture(tex, uv);
-	vec3 image_with_background = mix(vec3(mod(floor(uv.x*32.0)+floor(uv.y*32.0), 2.0)), image.xyz, image.a);
-	float lines_color = 0.5*(cos(5.0*TIME+100.0*(uv.x+uv.y))+1.0);
-	COLOR = vec4(mix(image_with_background, vec3(lines_color), step(is*min(m2.x, m2.y), 1.0)), 1.0);
-}"
 
 [sub_resource type="ShaderMaterial" id=2]
 resource_local_to_scene = true
 shader = SubResource( 1 )
-shader_param/size = Vector2( 585, 492 )
 
-[node name="Preview2D" type="ColorRect"]
+[node name="Preview2D" type="ColorRect" groups=[
+"preview",
+]]
 material = SubResource( 2 )
 anchor_right = 1.0
 anchor_bottom = 1.0
@@ -39,4 +25,16 @@ script = ExtResource( 1 )
 __meta__ = {
 "_edit_use_anchors_": false
 }
+shader = "uniform vec2 size;
+
+void fragment() {
+	float ms = max(size.x, size.y);
+	vec2 uv = fract(0.5+1.2*(UV-vec2(0.5))*ms/size.yx);
+	float is = min(size.x, size.y)/1.2;
+	vec2 m2 = min(fract(uv), 1.0-fract(uv));
+	vec4 image = preview_2d(uv);
+	vec3 image_with_background = mix(vec3(mod(floor(uv.x*32.0)+floor(uv.y*32.0), 2.0)), image.xyz, image.a);
+	float lines_color = 0.5*(cos(5.0*TIME+100.0*(uv.x+uv.y))+1.0);
+	COLOR = vec4(mix(image_with_background, vec3(lines_color), step(is*min(m2.x, m2.y), 1.0)), 1.0);
+}"
 [connection signal="resized" from="." to="." method="on_resized"]