sample test rope circle uv texture.

circle_ring_rope.gd

@tool
extends MeshInstance3D

@export var rope_length: float = 5.0  # Total length of the rope
@export var segments: int = 20  # Number of segments
@export var radius: float = 0.1  # Thickness of the rope
@export var sides: int = 8  # Number of sides for the rope's cross-section

func _ready() -> void:
	generate_rope()

func _process(_delta: float) -> void:
	if Engine.is_editor_hint():  # Update in editor for @tool
		generate_rope()

func generate_rope() -> void:
	# Create or get the ImmediateMesh
	if mesh == null:
		mesh = ImmediateMesh.new()
	else:
		mesh.clear_surfaces()

	# Begin drawing the mesh
	mesh.surface_begin(Mesh.PRIMITIVE_TRIANGLES)

	# Generate points along a simple straight line (modify for curves if needed)
	var points: Array[Vector3] = []
	for i in range(segments + 1):
		var t: float = float(i) / segments
		points.append(Vector3(0, -t * rope_length, 0))  # Straight down

	# Generate the rope mesh by creating a tube along the points
	for i in range(segments):
		var p0: Vector3 = points[i]
		var p1: Vector3 = points[i + 1]

		# Calculate the direction and basis vectors for the cross-section
		var dir: Vector3 = (p1 - p0).normalized()
		var right: Vector3 = dir.cross(Vector3.UP).normalized()
		if right == Vector3.ZERO:  # Handle edge case for vertical direction
			right = dir.cross(Vector3.FORWARD).normalized()
		var up: Vector3 = dir.cross(right).normalized()

		# Create vertices for the current and next cross-section
		for j in range(sides):
			var angle0: float = j * TAU / sides
			var angle1: float = (j + 1) * TAU / sides

			# Vertices for the current segment's cross-section
			var v0: Vector3 = p0 + radius * (cos(angle0) * right + sin(angle0) * up)
			var v1: Vector3 = p0 + radius * (cos(angle1) * right + sin(angle1) * up)
			var v2: Vector3 = p1 + radius * (cos(angle0) * right + sin(angle0) * up)
			var v3: Vector3 = p1 + radius * (cos(angle1) * right + sin(angle1) * up)

			# Normals (pointing outward from the rope's surface)
			var n0: Vector3 = (cos(angle0) * right + sin(angle0) * up).normalized()
			var n1: Vector3 = (cos(angle1) * right + sin(angle1) * up).normalized()

			# UVs (simple cylindrical mapping)
			var uv0: Vector2 = Vector2(float(j) / sides, float(i) / segments)
			var uv1: Vector2 = Vector2(float(j + 1) / sides, float(i) / segments)
			var uv2: Vector2 = Vector2(float(j) / sides, float(i + 1) / segments)
			var uv3: Vector2 = Vector2(float(j + 1) / sides, float(i + 1) / segments)

			# Add triangles with correct counterclockwise winding order for front face
			# Triangle 1: v0, v2, v1 (counterclockwise when viewed from outside)
			mesh.surface_set_normal(n0)
			mesh.surface_set_uv(uv0)
			mesh.surface_add_vertex(v0)
			mesh.surface_set_normal(n0)
			mesh.surface_set_uv(uv2)
			mesh.surface_add_vertex(v2)
			mesh.surface_set_normal(n1)
			mesh.surface_set_uv(uv1)
			mesh.surface_add_vertex(v1)

			# Triangle 2: v1, v2, v3 (counterclockwise when viewed from outside)
			mesh.surface_set_normal(n1)
			mesh.surface_set_uv(uv1)
			mesh.surface_add_vertex(v1)
			mesh.surface_set_normal(n0)
			mesh.surface_set_uv(uv2)
			mesh.surface_add_vertex(v2)
			mesh.surface_set_normal(n1)
			mesh.surface_set_uv(uv3)
			mesh.surface_add_vertex(v3)

	# End the surface
	mesh.surface_end()

	# Assign a material (optional, for visibility in editor)
	if material_override == null:
		var mat = StandardMaterial3D.new()
		mat.albedo_color = Color.GRAY
		mat.cull_mode = StandardMaterial3D.CULL_BACK  # Ensure backface culling
		material_override = mat