Dissolution

extends Node

var shapes: Node3D


func _ready() -> void:
	_add_environment()
	_add_light()

	var material: ShaderMaterial = ShaderMaterial.new()
	material.shader = Get.shader('dissolve')
	material.set_shader_parameter('noise_texture', _make_noise())

	shapes = Node3D.new()
	add_child(shapes)

	var meshes: Array[Mesh] = [SphereMesh.new(), BoxMesh.new(), TorusMesh.new()]

	for i in meshes.size():
		var item: MeshInstance3D = MeshInstance3D.new()
		item.mesh = meshes[i]
		item.material_override = material
		item.position = Vector3((i - 1) * 1.9, 0, 0)
		shapes.add_child(item)

	var camera: Camera3D = Camera3D.new()
	camera.position = Vector3(0, 1.1, 4.6)
	add_child(camera)
	camera.look_at(Vector3.ZERO, Vector3.UP)
	camera.current = true

	print('the noise texture comes from GDScript, the discard happens in the shader')


func _process(delta: float) -> void:
	for shape in shapes.get_children():
		shape.rotate_y(delta * 0.6)


func _make_noise() -> NoiseTexture2D:
	var noise: FastNoiseLite = FastNoiseLite.new()
	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX
	# a high frequency shreds the mesh into dust and the burning edge goes with it
	noise.frequency = 0.012

	var texture: NoiseTexture2D = NoiseTexture2D.new()
	texture.noise = noise
	texture.seamless = true
	texture.width = 256
	texture.height = 256

	return texture


func _add_environment() -> void:
	var sky_material: ProceduralSkyMaterial = ProceduralSkyMaterial.new()
	sky_material.sky_top_color = Color(0.04, 0.05, 0.1)
	sky_material.sky_horizon_color = Color(0.12, 0.14, 0.22)
	sky_material.ground_bottom_color = Color(0.02, 0.02, 0.04)
	sky_material.ground_horizon_color = Color(0.09, 0.1, 0.15)

	var sky: Sky = Sky.new()
	sky.sky_material = sky_material

	var env: Environment = Environment.new()
	env.background_mode = Environment.BG_SKY
	env.sky = sky
	env.ambient_light_source = Environment.AMBIENT_SOURCE_SKY
	env.ambient_light_energy = 0.7
	env.glow_enabled = true

	var world: WorldEnvironment = WorldEnvironment.new()
	world.environment = env
	add_child(world)


func _add_light() -> void:
	var light: DirectionalLight3D = DirectionalLight3D.new()
	light.rotation_degrees = Vector3(-45, -35, 0)
	light.light_energy = 1.8
	add_child(light)

shader_type spatial;
render_mode cull_disabled;

uniform sampler2D noise_texture;
uniform vec3 base_color: source_color = vec3(0.12, 0.32, 0.75);
uniform vec3 edge_color: source_color = vec3(1.0, 0.5, 0.1);
uniform float edge_width = 0.07;
uniform float speed = 0.35;

void fragment() {
	float n = texture(noise_texture, UV).r;
	// the range stops at 0.72, at 1.0 the whole mesh is gone and the scene is empty
	float threshold = mix(0.05, 0.72, abs(sin(TIME * speed)));

	if (n < threshold) {
		discard;
	}

	float edge = 1.0 - smoothstep(threshold, threshold + edge_width, n);

	ALBEDO = base_color;
	ROUGHNESS = 0.4;
	EMISSION = edge_color * edge * 4.0;
}