Code Pieces

Various code i stole from everywhere.

Simple FPS Controller

from Pastebin

extends CharacterBody3D

const SPEED = 5.0
const JUMP_VELOCITY = 4.5

# Get the gravity from the project settings to be synced with RigidBody nodes.
var gravity: float = ProjectSettings.get_setting("physics/3d/default_gravity")

@onready var camera: Camera3D = $Camera3D

func _ready() -> void:
    Input.mouse_mode = Input.MOUSE_MODE_CAPTURED


func _unhandled_input(event: InputEvent) -> void:
    if event is InputEventMouseMotion:
        rotate_y(-event.relative.x * .005)
        camera.rotate_x(-event.relative.y * .005)
        camera.rotation.x = clamp(camera.rotation.x, -PI/4, PI/4)

    if Input.is_action_just_pressed("ui_cancel"):
        get_tree().quit()


func _physics_process(delta: float) -> void:
    # Add the gravity.
    if not is_on_floor():
        velocity.y -= gravity * delta

    # Handle Jump.
    if Input.is_action_just_pressed("ui_accept") and is_on_floor():
        velocity.y = JUMP_VELOCITY

    # Get the input direction and handle the movement/deceleration.
    # As good practice, you should replace UI actions with custom gameplay actions.
    var input_dir := Input.get_vector("left", "right", "forward", "back")
    var direction := (transform.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()
    if direction:
        velocity.x = direction.x * SPEED
        velocity.z = direction.z * SPEED
    else:
        velocity.x = move_toward(velocity.x, 0, SPEED)
        velocity.z = move_toward(velocity.z, 0, SPEED)

    move_and_slide()

Generate mesh with blend surfaces, example

from Pastebin

extends Node3D

#godot 4, generate mesh with blend surfaces, example
func _ready():
    var mesh_instance = MeshInstance3D.new()
    add_child(mesh_instance)

    var mesh = ArrayMesh.new()
    var arrays = []
    arrays.resize(Mesh.ARRAY_MAX)
    arrays[Mesh.ARRAY_VERTEX] = PackedVector3Array([Vector3(1,0,0), Vector3(0,0,0), Vector3(0,1,0)])
    var arrays1 = []
    arrays1.resize(Mesh.ARRAY_MAX)
    arrays1[Mesh.ARRAY_VERTEX] = PackedVector3Array([Vector3(-1,0,0), Vector3(0,0,0), Vector3(0,-1,0)])

    var blend_shape_arrays = []
    blend_shape_arrays.resize(Mesh.ARRAY_MAX)
    blend_shape_arrays[Mesh.ARRAY_VERTEX] = PackedVector3Array([
        Vector3(1, 0.5, 0),
        Vector3(0, 0.5, 0),
        Vector3(0, 1.5, 0)])

    var blend_shape_arrays1 = []
    blend_shape_arrays1.resize(Mesh.ARRAY_MAX)
    blend_shape_arrays1[Mesh.ARRAY_VERTEX] = PackedVector3Array([
        Vector3(1, -0.5, 0),
        Vector3(0, -0.5, 0),
        Vector3(0, -1.5, 0),])

    mesh.add_blend_shape('bs')
    mesh.add_blend_shape('bs1')
    #mesh.add_blend_shape('bs2')

    mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLE_STRIP, arrays, [blend_shape_arrays,blend_shape_arrays1])


    #mesh.add_blend_shape('bs2')
    #mesh.add_blend_shape('bs3')
    mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLE_STRIP, arrays1, [blend_shape_arrays,blend_shape_arrays1])
    mesh_instance.mesh = mesh
    mesh_instance.set("blend_shapes/bs", .5)
    print(mesh.get_blend_shape_count())

Trails

var trail_time = xxx

func _spawn_fading_trail(from: Vector3, to: Vector3) -> void:
    var mesh := ImmediateMesh.new()
    mesh.surface_begin(Mesh.PRIMITIVE_LINES)
    mesh.surface_set_color(Color(0.941, 0.992, 0.008, 0.792))
    mesh.surface_add_vertex(from)
    mesh.surface_add_vertex(to)
    mesh.surface_end()
    var trail := MeshInstance3D.new()
    trail.mesh = mesh
    trail.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
    if tracer_material:
        trail.set_surface_override_material(0, tracer_material)
        get_tree().current_scene.add_child(trail)

    # Quick fade out by scaling alpha over time
    var t := get_tree().create_timer(trail_time)
    t.timeout.connect(func(): trail.queue_free())