attach

• GameObjects have an 'onpath' pointer, which complements the 'attach' pointer (to a gob).
• GobArea now implements the (horizontal) GPath API, returning always the same y coordinate, and checking that you're in the desired xrange.
• 'Ap' in a gobexpression will attach the object to a "path" rather than to an object, the area that triggered the collision will be used to define the new path.

GameObject::useEvent() should go away.(fr+)

crocform #1(en+)

Last week end, I finally got to the point where I wrote some script to give it existence in the ongoing 3-room demo. There's a thing that went significantly wrong, though: Bilou couldn't notice when the platform is gone.

La pyramide, c'est l'endroit idéal pour des plate-formes un peu particulières. Qui croulent, par exemple. Ou qui changent d'orientation. Mais quand j'ai voulu faire un p'tit essai dans ma démo actuelle, Bilou est resté gentiment à attendre que la plate-forme revienne, flottant dans le vide. En réalité, il me manque un évènement capable de "décrocher" Bilou de la plate-forme: puisqu'elle existe toujours, pour le jeu, on peut toujours marcher dessus.

Il y aurait plusieurs moyen de régler: Bilou peut déjà se faire "propulser" par une collision (hic: seulement s'il n'est pas au sol). Les dumbladors empilés détectent quand l'un d'eux s'en va (hic: seulement grâce à un contrôleur dédié et l'ajouter ici décalerait tous les évènements de Bilou). Au final, c'est le contrôleur testant si on est sur une plateforme que j'étends pour qu'il puisse tester un bit d'état de l'objet auquel on est attaché..

I've had a similar issue with dumbladors when time came to 'stack' them: when one recovered, those stacked on top of it had somehow to detect they'd no longer have a platform behind them. It would be trivial if the gameobject implementing the platform was destroyed, but here it stays around.

• extend dumblador's extra gobbit(when 7.1) to Bilou
• trigger an extra "throws up" temporary hitbox when flapping down the platform
• implement it all with brand new "larger animated blocks" feature, not with a sprite, because that platform doesn't truly "move".

Yet, I hesitate going for an additional micro-controller gobbit (despite it already has C++ code) because that would introduce new events to deal with. I'd rather have the onpath controller be able to fire an event when the platform-object it is attached to signals it is no longer a platform, the same way the controller can signal the object no longer exists.

I could try having some automated test into 'onpath' that would ensure the current state of the 'platform' object still has the area active and using the proper flags, but that would require extra care if I don't want Bilou to behave weirdly when the platform turns back or does any state transition that don't actually imply losing its 'platform' behaviour.

reality check: using onpath(when w7.2); (from the worst-possibly-named commit)

using between(fr+)

So, I now have fun ideas of how to use bridges in Bilou: Dreamland. Sounds like it could be a good idea to also figure out how I'm going to implement such things with my game engine... One thing is almost obvious: the bridge will be made of a set of independent-but-interacting game objects. I'm not going to try and make it one big animated object. If I did, I'd have to manually adjust collision boxes for segments for every frame. That's not what it is for. Same observation applied to the Green Zone boss: Big Caterpillar. And much like the bridge, Big Caterpillar is made of segments that must be able to interact to give the illusion of a single object.

Mais revenons un cran en arrière, voulez-vous ? Alors que J.L.N était face à son premier mini-boss dans Minish Cap, je me suis mis à prendre quelques notes sur le type de contrôleurs qu'il faudrait ajouter à mon moteur de jeu pour pouvoir faire quelque-chose de ce genre. Puis, sur la lancée, à ce que je pouvais en tirer comme conclusions pour la réalisation de Big Caterpillar, le boss de la Green Zone.

Il y a déjà une chose que le moteur de jeu de School Rush peut faire: c'est attacher un Gob (objet mobile fait de sprite(s)) à un autre, et utiliser sa position dans certains contrôleurs. C'est ainsi p.ex. que la chauve-souris-baie se dirige vers Bilou. ou que SpongeBop sait se balancer au bout d'un clou. C'est encore comme ça qu'on peut transporter un dumblador et que ses pieds le suivent à la trace. Mais dans tous ces exemples, on a un seul objet de référence et un objet référent. Quand il y a plusieurs référents (3 BerryBats) pour un même objet de référence (Bilou), ils s'ignorent les uns les autres. Or, pour permettre de positionner les segments internes de Big Caterpillar entre sa tête et sa queue, il faut les coordonnées des deux autres. C'est forcé :P

So since I've just been studying a bit how BC could be implemented, let's see what it can teach us. The game engine can attach one Gob to another one. That's how SpongeBop swings and how BerryBat aim at their target. It is quite clear that those "attach" links will play a role in animating BC, but the question is "who should be attach with whom, and why". When BC will be crawling, for instance, it is easy to make his head move forward during the "expanse" phase and then make the tail move forward (while the head is stopped) in the "contract" phase. As the distance between head and tail shrinks or grows, the location of other segments should adjust.

It is quite easy to find math expression for those locations based on head and tail coordinates. Unfortunately, that'd require *two* attach links per segment, and the game engine only handle one (including in expression opcodes to attach and detach things when collisions occur). I either have to revise the whole engine and break the assumption that One Attach Link Shall Be Enough For Everybody, or I have to come up with some clever way out. That way out could be how a between(...) controller could use not only the attached gob as a reference, but also *the one to which that is attached*. I.e. segments are all attached to the tail, tail is attached to the head and when segment is processed, it reads segment.attach == tail and tail.attach == head to get the data it needs.

Let's see whether that can be enough. I also long for the opportunity to have swinging vines in some Bilou game. They could also be made of chained Gob through attach links. At least when they're hanging free. But as soon as Bilou is using them, I'd like the rules to change. Now Bilou's position dictates how one part of the vine behaves because of tension. If we can use collision to re-write attachments when that happens, that turns into a job for between(...) again.

Retournons vers le pont en faisant une halte à une autre mécanique que je tiens à faire apparaître dans Dreamlands: pouvoir s'accrocher à des trucs qui pendent. J'aimerais depuis longtemps que ce genre d'objet dans Bilou soit au moins aussi bien animé que dans le remake de Pharao's Curse par Lazycow. ce qui suppose

• un mouvement ondulant lorsque la liane est livrée à elle-même (pas de balancé excessif à la DKC)
• une certaine raideur quand Bilou s'y accroche (pas question de passer en mode 'corde ninja')
• Si Bilou n'est pas au bout de la corde, l'extrémité libre continue d'agir librement alors que la moitié tendue est entièrement contrainte par la position de Bilou et celle du point d'attache.

Si j'essaie de dessiner des petites flèches rouges sur ce schéma pour représenter "qui a besoin de connaître la position de qui", on voit que la corde devra réorganiser ces liens quand elle passe d'un "état" à l'autre. Normalement, c'est jouable avec des collision. Et ça confirme mon intuition construite avec Big Caterpillar: le jeu, c'est d'avoir les deux points de référence (début et fin) qui sont directement liés l'un à l'autre (fin->attach == debut) et un contrôleur between() qui suit segment->attach pour trouver fin puis fin->attach pour avoir début et détermine la position-cible à partir des positions de fin et début.

Et pour le pont ? Va-t-il forcément falloir deux liens par bûche ? Je crois que non, mais ça supposera de faire apparaître à la volée deux objets "coincés" par collision sous la bûche qui a reçu un poids, chacun étant la fin d'une chaîne qui remonte jusqu'à un des points d'attache du pont. Et donc que la largeur maximale pour les zones de collision déterminera la largeur maximale du pont.

In Theory, it should be possible to do something similar with the bridge, at least to get a nice alignment of the logs when the force applied is so strong that logs' weights becomes neglectible in comparison. Yet, it's obvious there will be two chains here, both using the same "origin" location (the log on which the force is applied). I thought it could be fixed by creating temporarily two GOBs (red dashes) that are pushed by a collision box of the weighted log (red hatching), each being attached to either side of the bridge (red circles). "slave" logs that must just align would then attach to the dashed-GOB that's on their side (green arrows). But maybe we could even do it without the dashed-GOBs if sides attached to the weighted log and not the other way round.

Newer collision flags(?)

That issue is not new: it already appeared when I wanted to add pick-and-throw mechanism together with get-your-feet-back while I was just done with direction tiles for inkjet. Each of these would require about 4 different type of "messages" exchanged between game object and I had barely more than 8 flags left... And the solution had been to use some combination of bits for the different things. So you'd still have 0010 saying "up" and 0020 saying "down", but that would only be valid in connection with 0100 that says "direction tile" and not with 0400 that says "interplay" or with 0800 that has been used to collect feet and animate ink level in pipes.

And well, introducing bridges and things like that could easily use more casts to keep good performances: both heroes and baddies will collide with bridges, but that doesn't requires baddies to test each others to work. And likely only part of the bridge internal.

I had collected a set of questions on my new notes, and one of the first one got its answer: despite we have only 16 bits communicated to the script about what truly happened in a collision, a full 32-bit number is stored internally. Some of the high bits are already use for special purpose such as "keep checking collision even after a first item was found" or "only consider objects attached to me", but plenty others could be used to restrict the scope, e.g. creating a private "namespace" between blador and blador feet so that the feet cannot accidentally attach to an inkjet (although maybe that's redundant with "must be attached to me"). It makes little sense to keep the upper 16-bits as "flags" and process them the same way the lower 16-bits are processed (a single matching bit and bingo, we have a collision) because we would be unable to identify which flag had a match. Did we caught fire ? or get smashed ? or got an electric shock ? no way to find out.

So the plan would be the following:

• 8 "casts" (lists) seems a good number. Each test area indicates exactly which cast it tests. If we have casts Evil and Bridge and need to test both for STOMP, then 2 test areas are needed.
• two "control" bits: ALL and ATTACH
• 16 "flags" bit: a collision occur as soon as two masks have at least one in common
• 8 "namespace" bit: a collision occur only if the two area exactly use the same namespace
• any other are reserved for future extensions.