Implement standing on moving platform

This worked immediately, wtf

MovingPlatform.gd

@@ -4,6 +4,7 @@ class_name MovingPlatform
 
 var time_passed := 0.0
 var distance_to_pivot := 0.0
+var velocity := Vector3.ZERO
 
 export(float) var move_speed = 2.0
 export(NodePath) var solar_system
@@ -20,11 +21,17 @@ func _process(delta):
 	time_passed += delta
 	var speed_multiplier = (1.0 / distance_to_pivot) * move_speed
 	
+	var translation_before = translation
+	
 	translation = Vector3(0.0,
 			cos(time_passed * speed_multiplier) * distance_to_pivot,
 			sin(time_passed * speed_multiplier) * distance_to_pivot
 	)
 	
+	velocity = (translation - translation_before) / delta
+	
+	print(velocity)
+	
 	# Rotate according to gravity
 	var gravity_acceleration = get_node(solar_system).get_gravitation_acceleration(global_transform.origin)
 	

Planet.gd

@@ -1,4 +1,11 @@
 extends StaticBody
+class_name Planet
 
 
 export(float) var mass
+export(float) var rotate_speed := 0.0
+
+
+func _process(delta):
+	rotate_y(rotate_speed * delta)
+	

Player.gd

@@ -18,6 +18,8 @@ var time_since_jump_start := 0.0
 var initial_jump_burst = 10.0
 var jump_exponent = 0.05
 
+var current_target_velocity := Vector3.ZERO
+
 export(NodePath) var solar_system
 
 
@@ -32,7 +34,10 @@ func _input(event):
 
 func apply_acceleration(acceleration):
 	# First drag, then add the new acceleration
-	velocity *= 1 - drag
+	# For drag: Lerp towards the target velocity
+	# This is usually 0, unless we're on something that's moving, in which case it is that object's
+	#  velocity
+	velocity = lerp(velocity, current_target_velocity, drag)
 	velocity += acceleration
 
 
@@ -61,7 +66,12 @@ func _physics_process(delta):
 	
 	# Handle jumping
 	if jumping:
-		var e_section = max(exp(log(initial_jump_burst - 1 / jump_exponent * time_since_jump_start)), 0.0000001)
+		# Continuously apply an impulse by adding velocity: a lot at first, then less until it's 0
+		# Use max() to avoid NaN from being applied once no more impulse should be added
+		var e_section = max(
+			exp(log(initial_jump_burst - 1 / jump_exponent * time_since_jump_start)),
+			0.0
+		)
 		velocity += -gravity_acceleration.normalized() * e_section
 		time_since_jump_start += delta
 	
@@ -70,8 +80,17 @@ func _physics_process(delta):
 	#move_and_slide(velocity, -gravity_acceleration.normalized(), true)
 	var collision = move_and_collide(velocity * delta)
 	
-	if collision and not jumping:
+	if collision:
+		if collision.collider.is_in_group("MovingPlatform"):
+			# Inherit the moving platform's velocity
+			current_target_velocity = collision.collider.velocity
+			velocity = current_target_velocity
+		if not jumping:
 			on_ground = true
+	else:
+		# We're not colliding with anything, so drag takes us towards 0
+		current_target_velocity = Vector3.ZERO
+		
 	
 	# Clamp the velocity just to be save
 	velocity.x = clamp(velocity.x, -MAX_VEL, MAX_VEL)
@@ -84,5 +103,6 @@ func _physics_process(delta):
 	var angle = local_down.angle_to(down)
 	var axis = local_down.cross(down).normalized()
 	
-	if axis != Vector3.ZERO: # Happens if we're perfectly aligned already (local_down and down are equal)
+	# An axis of 0 happens if we're perfectly aligned already (local_down and down are equal)
+	if axis != Vector3.ZERO:
 		rotate(axis, angle)

World.tscn

@@ -108,7 +108,9 @@ glow_bloom = 0.1
 [node name="MovingPlatformPivot" type="Position3D" parent="."]
 transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, -20, 0 )
 
-[node name="MovingPlatform" type="KinematicBody" parent="MovingPlatformPivot"]
+[node name="MovingPlatform" type="KinematicBody" parent="MovingPlatformPivot" groups=[
+"MovingPlatform",
+]]
 transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 30, 0 )
 script = ExtResource( 5 )
 solar_system = NodePath("../../Planets")

project.godot

@@ -14,6 +14,11 @@ _global_script_classes=[ {
 "language": "GDScript",
 "path": "res://MovingPlatform.gd"
 }, {
+"base": "StaticBody",
+"class": "Planet",
+"language": "GDScript",
+"path": "res://Planet.gd"
+}, {
 "base": "Spatial",
 "class": "SolarSystem",
 "language": "GDScript",
@@ -21,6 +26,7 @@ _global_script_classes=[ {
 } ]
 _global_script_class_icons={
 "MovingPlatform": "",
+"Planet": "",
 "SolarSystem": ""
 }