[wookieejedi]

Release of Custom-Movements-SEXPs
Custom sexps and functions for FSO that allow for much easier ship movements and rotations.
v2.7 (December 13, 2024)




TLDR: Release of custom sexps which can make cap ship (or any ship) movements much easier and more natural looking.

Background
Do you ever get frustrated when trying and get large ship movements to look good? I've found this be especially tricky if you want the ships to act dynamically, if you want big ships to rotate in a way that looks natural, or if you want many big ships to follow a leader ship and stay in a relative formation. Dynamic waypoints provide an invaluable tool, yet ships will stop following a waypoint path once the path is complete or immediately turn around to start the path again. I wanted a single sexp that told a ship to track a waypoint or ship, thus the ship would travel to the waypoint and then move again if the waypoint moved.

It can be similarly tricky to get large ships to rotate to a certain orientation. The rotation maneuver sexp is useful but you aren't guaranteed that the ship will stop rotating when it reaches the desired orientation. Again, I wanted a single sexp that I could use once that would move a ship to a specified orientation with a natural looking movement.

Also, recent updates have focused on making scripted movements look natural and precise. For example, values in the sexp can be set to have ships precisely stop on waypoints, then use the natural AI methods to rotate. There’s also the addition of a 'semi-smart' waypoint order, where AI ships following waypoints will check for obstacles in their path, then stop if they are on course to hit something. Once the obstacle leaves then the path will resume.

To achieve these goals, I developed a suite of custom lua sexps, and hopefully you might find something useful to your own missions!


Overview
In this release I have included sexps to rotate ships to a specific orientation, have a waypoint track a ship, a ship track a waypoint, and a ship track another ship. Fun things you can do with these sexps is to have entire fleet all rotate to the same orientation, have a battle group of ships follow around a leader command ship, order AI capships to 'attack' an enemy craft by pulling up next to it and rotating 90 degrees to bring broadsides to bear, ordering a ship track a target orientation, and many other things.


Gritty Details
The following custom lua sexps are included:
 
move-to-orientation and move-to-face-object
Moves a ship to a given orientation over a specified time duration. This sexp only has to be called once and can be used to make a much more natural looking rotational effect for ships. By default this sexp will issue a play-dead-persistent order with priority 200, but this priority value can be changed and the order can also not be issued. Also by default it will use the ship's tabled rotational velocity to make the rotation look natural.

early-stop-move-to-orientation
Immediately terminates the custom `move-to-orientation` and 'move-to-face-object' sexps for a ship. Only use this sexp to prematurely stop these rotations for a ship.

add-waypoint-track-ship
Sets a waypoint to a position relative to a ship or waypoint continually. This sexp is an easier way to make a dynamic waypoint track a ship location. The waypoint will be moved to the specified coordinates relative to the ship at every time duration. If the ship is not present or destroyed, or departed then the waypoint will not update location.

remove-waypoint-track-ship
Removes a waypoint tracking of a ship. This sexp removes the effect of 'add-waypoint-track-ship'.

add-ai-goal-track-waypoint
Adds a custom ai-goal for a ship to track a waypoint path. The ship will move to the final point in the waypoint path and remain in that position. If the waypoint path is moved the ship will follow the waypoint path again. Useful for having ships follow dynamic waypoints. Note, this order can only be removed via the sexps 'remove-ai-goal-track-waypoint' or 'clear-goals'.

pause-ai-goal-track-waypoint
pauses a custom `add-ai-goal-track-waypoint` goal, which is very useful if you want to pause a ship-track-waypoint or ship-track-ship order without removing it and then having to re-add it will all options again. The specified ship will stop moving along the waypoint path and remain still (though it will still hold it's goal).

remove-ai-goal-track-waypoint
Removes a custom `add-ai-goal-Track-Waypoint` goal.

set-idle-track-orientation
Sets an idle/resting orientation for a ship tracking a waypoint, either as an absolute orientation or an orientation relative to a given ship. When a ship that is tracking a waypoint is not moving forward it will move to this idle orientation. If a relative orientation is specified the sexp will get the target ship orientation and then add the pitch, bank, and heading values set in this sexp to create a final idle/resting orientation.

unset-idle-track-orientation
Unsets/removes the idle/resting orientation for a ship tracking a waypoint. This sexp will result in a ship tracking a waypoint to not attempt to change it's orientation when not moving.

add-ai-goal-track-ship
Adds a custom ai-goal for a ship to track another ship. The ordered ship will move to follow the target ship and then once stopped will rotate to the target ship orientation, or a variant to that orientation. This is a higher level sexp that runs 'add-Waypoint-Track-Ship' with 'add-ai-goal-Track-Waypoint' and 'set-Idle-Track-Orientation'.

remove-ai-goal-track-ship
Removes a custom ai-goal for a ship to track another ship. This is a higher level sexp that runs 'remove-waypoint-track-ship' with 'remove-ai-goal-track-waypoint' and 'unset-idle-track-orientation'.

set-bank-constant
Sets the bank constant of a given ship. Bank constant is the amount of roll (bank) a ship does when turning (yawing).

set-deceleration-time
Sets the deceleration time of a given ship. Setting this to 0 will ensure that ships stop precisely at waypoints. Note, stopping may look a bit rigid if the ship is going very fast. You can reset the value to the tabled value by using a negative number.

set-acceleration-time
Sets the acceleration time of a given ship. Setting this to the same value on a group of ships can be useful to ensure consistent movement. You can reset the value to the tabled value by using a negative number.


Usage:
Download these two files from https://github.com/wookieejedi/FSO-Scripts/tree/master/Movements-SEXPs and then place them in your data/tables folder. Then just open FRED and you will see a new listing called LUA-Movements where all the sexps are located. There are detailed descriptions of each sexp and each argument.


Important! You need an FSO build of August 24, 2022 or newer for these to work.

I included an example mission that shows how to use the 'move-to-orientation' and the 'add-ai-goal-track-ship' which is a higher order sexp that runs 'add-waypoint-track-ship' with 'add-ai-goal-track-waypoint' and 'set-idle-track-orientation'.


Change Log

Code: [Select]

v2.7: Added 'pause-ai-goal-track-waypoint' and improved 'smart-stop' collision tests in close-quarters.
v2.6: Updated with new sexp 'set-acceleration-time' and allowed resetting to tabled value for this and 'set-deceleration-time'
v2.5: Updated internal code with some cleanup and extra error checking.
v2.4: Added `set-pos-to-rand-pos-in-b-box` lua sexp.
v2.3: Minor optimization and code cleanup. Also added `get-waypoint-speed-cap` and `set-pos-to-rand-pos-on-hull` lua sexps. 
v2.2: add new sexp 'move-to-face-object` and expanded ability of `add-waypoint-track-ship`.
v2.1: add semi-smart waypoint follow option.
v2.0: updated default rotation to fully use FSO ship AI, so rotations now look completely natural if using the default rotation time.
v1.8: added new sexps for precise big ship physics and changed default to not enable play-dead-persistent.
v1.7: Added safety checks to ensure scripts do not run in multiplayer.
v1.6: Fixed default calculation of ship tracking distance if none was specified.
v1.5: Fixed bug with auto turning time calculation.
v1.4: Exposed some more options to the user.
v1.3: Fixed occasional ship spinning occurrences.
v1.2: Added extra error checking for a few spots and more helpful debug messages.
v1.1: Added track orientation behavior. Now ships will also maintain the specified orientation to their specified target, even if the target rotates or moves. Thanks for the suggestion General Battuta!
v1.0: First release.


Finally, I would be happy to answer any questions and hope you can find something that is useful for your own missions!

[mjn.mixael]

Very cool. I almost certainly have use for some of these.

[wookieejedi]

Great! If there is any extra functionality you wanted added that may be useful just let me know.

[Nightmare]

Good work!

[General Battuta]

Great! If there is any extra functionality you wanted added that may be useful just let me know.

My holy grail of movement SEXPs is 'hold relative orientation' (or 'hold relative aspect' or whatever). Tells a ship to position itself in a point, say, 500 meters beneath the target's origin, maintain that point relative to the target no matter how the target maneuvers, and hold its own orientation respect to the target.

Or, in other words: "go to 500 below the target's origin and keep your top facing that origin no matter what."

Probably really hard.

[wookieejedi]

Great! If there is any extra functionality you wanted added that may be useful just let me know.

My holy grail of movement SEXPs is 'hold relative orientation' (or 'hold relative aspect' or whatever). Tells a ship to position itself in a point, say, 500 meters beneath the target's origin, maintain that point relative to the target no matter how the target maneuvers, and hold its own orientation respect to the target.

Or, in other words: "go to 500 below the target's origin and keep your top facing that origin no matter what."

Probably really hard.

Alright, just added that functionality (github also updated). That is now the default behavior for `add-ai-goal-track-ship` and you can also turn that behavior on and off using `set-idle-track-orientation`. So now you can really tell a ship to go to a spot relative to another ship and keep it's nose pointed at it no matter what

[General Battuta]

Without looking - how do you specify whether you want the mover to aim their nose, top, bottom, or ass at the target? Or is it nose only?

[wookieejedi]

Without looking - how do you specify whether you want the mover to aim their nose, top, bottom, or ass at the target? Or is it nose only?

Good question, the user can specify what direction to aim. The inputs for `add-ai-goal-track-ship` takes, among other things, a pitch, bank, and heading that is relative to the target ship's orientation. So, say you wanted Ship A to pull up beneath Ship B and then rotate so it's butt is facing Ship B. To do that you would set the relative y location in `add-ai-goal-track-ship` to some negative value and then the pitch and heading of 0 and a pitch of 90 degrees (again these are relative to Ship B's orientation). These inputs to the sexp would tell Ship A to go to that position relative to Ship A and then point it's butt up in the air so the butt is facing Ship B.

The full sexp and all it's arguments for that higher order sexp are:

Code: [Select]

$Operator: add-ai-goal-track-ship
$Category: Change
$Subcategory: LUA-Movements
$Minimum Arguments: 3
$Maximum Arguments: 10
$Return Type: Nothing
$Description: Adds a custom ai-goal for a ship to track another ship. The ordered ship will move to follow the target ship and then once stopped will rotate to the target ship orientation, or a variant to that orientation. This is a higher level sexp that runs 'add-waypoint-track-ship' with 'add-ai-goal-track-waypoint' and 'set-idle-track-orientation'. This sexp uses a time interval of 1 second for updating positional data and a track distance of the radius of the ship following the track order. Note, use a waypoint path with only 1 waypoint. The order 'clear-goals' will also stop this custom order. Also the ship will continually maintain the specified orientation when at rest.
$Parameter:
+Description: Ship to order.
+Type: Ship
$Parameter:
+Description: Target ship to track.
+Type: Ship
$Parameter:
+Description: Waypoint path to use for the ship to follow.
+Type: Waypointpath
$Parameter:
+Description: Priority of order. Default is 100.
+Type: Number
$Parameter:
+Description: X offset in meters from the center of the target ship that the ordered ship will move to. Default is random value between the radius and diameter of the target ship.
+Type: Number
$Parameter:
+Description: Y offset in meters from the center of the target ship that the ordered ship will move to. Default is random value between the radius and diameter of the target ship.
+Type: Number
$Parameter:
+Description: Z offset in meters from the center of the target ship that the ordered ship will move to. Default is random value between the radius and diameter of the target ship.
+Type: Number
$Parameter:
+Description: Pitch of idle orientation in degrees relative to target ship orientation. Default is 0 (same pitch as target). Any value is valid and will be converted to range within 0-359.
+Type: Number
$Parameter:
+Description: Pitch of idle orientation in degrees relative to target ship orientation. Default is 0 (same bank as target). Any value is valid and will be converted to range within 0-359.
+Type: Number
$Parameter:
+Description: Pitch of idle orientation in degrees relative to target ship orientation. Default is 0 (same heading as target). Any value is valid and will be converted to range within 0-359.
+Type: Number


[General Battuta]

Fantastique! This will be amazing for capship choreography, especially in capship command missions.

[wookieejedi]

Thanks, glad it will be helpful. If you or anyone else comes across anything that you’d like added just let me know and I can see what I can do!

[0rph3u5]

I am certainly going to get some use out of these for Pendragon - even though my stated goal is to get rid of capital ships more and more...

[wookieejedi]

Excellent! Also I just updated the main -sct file on github. V1.2 provides additional validity checks for certain functions and more helpful debug messages.

[Nightmare]

Sorry to bump here, but what would you think of having a common HLP scripting repo on github or elsewhere?

[wookieejedi]

No worries, I'd say that's a good idea. Even just a stickied board where there are links to active scripters's githubs could work, too. Perhaps opening up a topic and getting other's feedback would be beneficial, too.

[Nightmare]

Will do!

[wookieejedi]

Note, updated script to version 1.3, which fixes occasional ship spinning occurrences.

[EatThePath]

These seem very useful, thank you for making them. I have some questions, though.

What is relative orientation relative to? Are you setting what where ship A is going to point it's nose relative to it's vector to ship B, or are you setting ship A's orientation to be an offset to ship B? I can imagine both being useful, the former for things like broadside fighting and the latter for holding formations of ships. I think you can probably ultimately accomplish both with either, but some are more straight-forward to use in certain ways than others.

With relative position offsets for tracking, does that relative position account for the orientation of the target ship as well, or is it in defaultly oriented coordinates just centered on the tracked ship?

Lastly, I find myself wanting a version of ai-goal-track that takes a distance rather than a vector for positional offset.

[wookieejedi]

Thanks, and all good questions.

What is relative orientation relative to?

Relative orientation is relative strictly to the target's orientation (so an offset to ship B). For example, if you want Ship A to be broadsides against Ship B then you would tell the sexp to use relative orientation and set the heading value as 90. Ship A will move to the waypoint, then rotate to an orientation that is 90 degrees different than Ship B.

Yes, relative position offsets account for the target ship's direction. So if you want Ship A to follow right behind Ship B then make the offset have a z value of some negative number. For example, if I set it to -300 for the z offset it will be 300 meters behind the ship, no matter what orientation that target ship is in.

For your last point, I think I see what you mean, but could you give an example just so I am sure?

[EatThePath]

For examples example, say I want a Ravana fly to 2000 m away from a target and point it's nose at that target, without caring if the target is twisting around itself, or a moloch to hold a broadside at a specific distance in a similar situation.

[wookieejedi]

For examples example, say I want a Ravana fly to 2000 m away from a target and point it's nose at that target, without caring if the target is twisting around itself, or a moloch to hold a broadside at a specific distance in a similar situation.

Ah I see, thank you for the examples. That would indeed be useful, and I have added that as an option in v1.4. There are two options to set to achieve that behavior. The sexp `ai-goal-track` now has two additional optional arguments to set to achieve that kind of behavior.

• Whether or not to use relative offsets. Default is true, which means all offsets will be relative to the target ship's orientation. To force the use of absolute offsets and not take account the ship's orientation, set to false.

• Boolean if the ship should actively mantain this orientation when at rest. Default is true. Keeping this value to true is useful for having a ship mantain an orientation relative to another ship, even if the target ship rotates. 

Also the option to disable or set the priority of the play_dead order used during ship rotations as also been added to the ship_track_ship sexp.