2nafish117 / godot-verlet-rope

Rope system inspired by half life 2

NOTE this plugin is meant for godot 3.x, and is not maintained for 4.x.

this is a great port of the plugin to 4.x https://github.com/Tshmofen/verlet-rope-4

Godot Verlet Rope

A fast implementation of verlet integration based rope physics, similar to the one seen in half life 2.

Quick Start

1. Add either rope node (VerletRopeGd/VerletRopeCs) to the scene and set the AttachEndTo property in the inspector to any Spatial derived node (hint: use another rope node to chain the ropes or a position node to end the chain).
2. To use a custom rope texture you will have to set the Albedo of the material in the inpector. Use a tiling texture and set the UV0 x property to change the tiling (some example tiling textures can be found in the demos).
3. If you are creating a custom rope material, remember to set Cull Mode to disabled for the rope to render on both sides (this mainly helps to see ropes clearly in editor mode).
4. Save an OpenSimplex noise as resource so you can reuse the same wind resource for all ropes. This allows for a global level wind so all ropes react to the same wind.
5. Add a VisibilityNotifier as a child to make rope draw only when the main camera is viewing it.
6. NOTE: Rotations on rope have been disabled because rotating it doesn't correctly end the rope at the attach_end_to point. Rotations are also not really needed, just move the endpoints instead.
7. NOTE: If you do make changes to VerletRopeGd.gd or VerletRopeCs.cs make sure to close and reopen the scene in the editor to stop some errors from piling up in the logs.

Featues

1. Verlet integration based particle simulation
2. Full rope simulation within the editor, set Simulate to off to stop the simulation.
3. Set number of particles, length, width and iterations for the rope.
4. PreprocessIterations processes the rope in _ready so it doesnt start out in a non rest position, a value of 20 is good enough, a higher value makes the scene load time longer.
5. Always faces the current camera in play mode
6. Automatically tesselates some sharp parts of the rope using Catmull rom splines to keep the rope looking smooth (use the SubdivLodDistance to change beyond what distance this tesselation stops).
7. VisibilityNotifier enables and disables drawing of the rope when the current camera is not viewing the rope. The rope automatically grows and shrinks the aabb, so you dont have to set the extents of the VisibilityNotifier yourself)
8. Enable/disable/configure forces like gravity, wind, air drag.
9. Rudimentary collisions using raycasts (only tests collisions if a collider enters its aabb), you need to enable this with ApplyCollisions.

Rope export params and functions

export variables	what it does
attach_start	attach/detach the start point
attach_end_to	attach end to any another Spatial by node path
rope_length	length of the rope
rope_width	width of the rope
simulation_particles	number of particles to simulate the rope. Odd number (greater than 3) is recommended for ropes attached on both sides for a smoother rope at its lowest point
iterations	number of verlet constraint iterations per frame, higher value gives accurate rope simulation for lengthy ropes with many simulation particles. Increase if you find the rope is sagging or stretching too much
preprocess_iterations	number of iterations to be precalculated in _ready() to set the rope in a rest position. Value of 20-30 should be enough.
simulation_rate	rate of simulation. lower the value if the rope is not going to move a lot or it is far away
stiffness	should be named elasticity. it is a fraction that controls how much the verlet constraint corrects the rope. value from 0.1 to 1.0 is recommended
simulate	on/off the simulation. NOTE: rope is still being drawn every frame if this is off.
draw	on/off the drawing. you will still see the rope because ImmediateGeometry.clear wasnt called, but the rope isnt being drawn every frame. NOTE: rope is still being simulated if this is off.
subdiv_lod_distance	does catmull rom spline smoothing (for required segments) at distances less than this
apply_gravity	on/off gravity
gravity	gravity vector
gravity_scale	a factor to scale the gravity vector
apply_wind	on/off wind
wind_noise	OpenSimplexNoise resource for the wind. noise period controls the turbulence(kinda). save resource to disk and share across ropes for a global wind setting.
wind	the wind vector
wind_scale	a factor to scale the wind vector
apply_damping	on/off air drag/damping. sometimes helps when rope bugs out to bring it back to rest.
damping_factor	amount of damping
apply_collision	on/off collision with bodies. collisions work best on smooth surfaces without sharp edges. collisions are checked only when a body enters the ropes AABB (axis aligned bounding box)
collision_mask	the collision mask to be used for collisions

functions	what it does
get_end_location	gets the coordinates of the end in global space
is_attached_start	is the start attached
is_attached_end	is the end attached

Creating ropes in code

# instance and add rope to scene
var rope = load('<path to verlet_rope.gd>').new()
add_child(rope)

# set its params
rope.preprocess_iterations = 0
rope.stiffness = 1.0
rope.rope_width = 0.02
rope.transform.origin = Vector3.ZERO
rope.attach_end_to = end_node.get_path()
rope.rope_length = 6.0
rope.simulation_particles = 7
var wind_noise = OpenSimplexNoise.new()
wind_noise.octaves = 1
wind_noise.period = 0.6
wind_noise.persistence = 1.0
rope.wind_noise = wind_noise
rope.wind = Vector3.RIGHT
rope.wind_scale = 5.0