NPC cargo: three questions

[LinuxOnTheDesktop]

1. If shipdata has

  "IST_derelict_Adder" = 
  {
    like_ship = "adder";
    ai_type = "nullAI.plist";
    max_cargo = 2;
    roles = "IST_derelict IST_derelictLive(0.1)";
    scan_class = "CLASS_CARGO";
    script = "IST_derelict_dead.js";
  };

will that ship be allocated cargo?

2. setCargoType relies upon facts about the status of types of cargo in the current system. How does that work in interstellar space?

3. Is there a simple way to allocate a random amount of random-content cargo to a NPC?

Thanks.

EDIT: I find the following. If in shipdata I set isHulk to yes, and remove the scan_class line, then the resulting ship appears yellow on the scanner (as against white) but still, in my testing so far, lacks cargo. Moreover, I find that if I try to add a ship script to a hulk, the script does not take.

[AhmedOthmn]

1-Setting max_cargo = 2 only defines the capacity of the ship's hold. Because your ship is using nullAI.plist and lacks a specific trading role, the game engine won't automatically fill it.

2-It will spawn empty. Standard cargo assignment functions look at the current system's planetary market data (exports/imports). Because interstellar space doesn't have a local economy, those market functions fail. Depending on the script, it will either throw a silent error or fall back to generic items like food.

3-And for why isHulk breaks your scripts (Regarding your edit)
This is a very common gotcha! When you set isHulk = yes, you are telling Oolite to classify the entity strictly as physical space debris. To save CPU cycles, the engine aggressively optimizes debris by stripping away all ship scripts and AI. That is exactly why your IST_derelict_dead.js script wouldn't run.

[LinuxOnTheDesktop]

Dear Ahmed

Thank you. Do you think then that I ought to revert to my previous - and, I had though, inefficient - way of doing things? To wit:

• in shipdata, give the ship a scan_class of 'CLASS_CARGO' (though I seem also to have had is_hulk = yes; perhaps that actually stopped the ship script from working and should be removed);
• have a ship script that contains the following.

this.shipTakingDamage = function(amount) {
	if (this.ship.energy > amount) return;
	if (this.ship.cargoSpaceCapacity === 0 || Math.random() > 0.15) return;
	this.ship.energy = 50; // ship is about to explode; keep it alive for a moment.
	var numOfPodsToEject;
	// . . . SNIP . . .
	this.ship.spawn("cargopod", numOfPodsToEject);
	this.ship.explode(true);
};

EDIT: After an escape pod has been ejected, a ship becomes white on the scanner, yes? However, is_hulk seems to set the scanner colour to yellow.

[LinuxOnTheDesktop]

I add the following. I am getting a hard crash - to desktop, with nothing in the log - when my ship-script does

this.ship.spawn("cargopod", 1); 

when the scan_class is CLASS_CARGO or CLASS_NEUTRAL (I have not tested other class values) and irrespective of whether is_hulk is set to yes.

EDIT: ah, actually, the crash occurs when I do this.ship.explode() - whether immediately after the spawning or on its own.

[AhmedOthmn]

I’d probably go back to the original approach, but remove 'is_hulk = yes'.

'max_cargo' is just the capacity, so it won’t automatically give the ship cargo. Having the script handle the cargo pods on destruction seems reasonable.

Also, I wouldn’t assume 'is_hulk' is the reason the script doesn’t run. The crash on 'this.ship.explode()' sounds like a separate issue. Since 'spawn("cargopod", 1)' works by itself, I’d test 'explode()' on its own and see whether that still crashes.

So basically:

plist
scan_class = "CLASS_CARGO";
script = "IST_derelict_dead.js";

and leave out "is_hulk".
The yellow scanner color is probably just the hulk/derelict classification, so you’d lose that by doing this, but I think it’s the safer route for a scripted derelict.

[phkb]

You're checking
if (this.ship.energy > amount) return;
at the beginning of your script. So, actually, the ship has already died whenever this condition fails and the rest of your code runs. Thus, when you get to this.ship.explode(); there is no ship to explode.

You could avoid using the shipTakingDamage event and instead use shipDied. You can still do the cargo spawning during that event.

[phkb]

And if you want to make a ship derelict without using the is_hulk property, do something like this:

this.$makeShipDerelict = function (shp) {
    shp.bounty = 0;
    // set script to default, to avoid a special script for the trader doing stuff. (like setting a new AI)
    shp.setScript("oolite-default-ship-script.js");
    shp.switchAI("oolite-nullAI.js");

    // remove any escorts that came with the ship
    if (shp.escorts) {
        var k = shp.escorts.length;
        while (k--) shp.escorts[k].remove(true);
    }

    shp.script.shipLaunchedEscapePod = this.$himsn_derelict_shipLaunchedEscapePod; // function to remove the escapepod after launch.
    if (shp.equipmentStatus("EQ_ESCAPE_POD") === "EQUIPMENT_UNAVAILABLE") shp.awardEquipment("EQ_ESCAPE_POD");
    shp.abandonShip(); // make sure no pilot is left behind and this command turns the ship into cargo.
    shp.primaryRole = "himsn_derelict"; // to avoid pirate attacks
    shp.displayName = shp.displayName + " (derelict)";
    shp.maxEnergy = 50;
    shp.lightsActive = false;
}

Just pass your ship object to this function.

[LinuxOnTheDesktop]

phkb: marvellous. Thanks to you and to Ahmed.