I’ve been testing a lot of concepts (some old, some new) with a test project and this post is about what I’ve learned, and what else needs to be explored.
CSVToDictionary and AJAX
It’s easier to maintain a separate text file for populating lookup dicts. Use the AJAX object to read the text and then CSVToDictionary to populate the dict. Remove the double-quote marks when using a text file. This makes it easier to read.
Newlines in text files
When extracting text using AJAX, newlines might be necessary, but escape characters do not seem to be recognised. Therefore, I ended up using escape characters, but had to process it (using search-replace) during extraction.
Containers have been extremely useful especially in terms of debugging messages. For every object I need to debug, a debug Text object is created, and querying the instance of the object will always point to the same objects of the container. No additional picking is necessary. This is probably the most important aspect of my testing.
There are no real enumerations in C2, but simply assigning a constant number to a recognisable variable name is good enough. For example, in the case where the z-layer of a logical position needs to be identified by keyword, I use
Although a topic unto itself, the main takeaway from doing AI, is how triggers are setup in Tiled and how it’s set up in C2 to respond to triggers.
There are area triggers, which are set up in Tiled. These are positional, and in the test project, they included a ‘facing’ property, which meant that the trigger is fired only when the player is facing a certain direction. The trigger’s name is the string that will end up being called by C2. I opted to use the ‘name’ attribute in Tiled instead of the relegating it to a property because it’s clearer to see the object name in the Tiled viewport.
Some triggers are set up in C2, especially other kinds of interactions. For example, talking to an NPC will yield a trigger specific to the interaction.
The C2 trigger itself is tied to a particular entity, whether it is another NPC, or some other object. That object is responsible for keeping track of the global trigger calls, and what is relevant to itself. For example, if a certain trigger is called 3 times, the object must keep track that it has heard those 3 triggers, and act accordingly. As such, two variables are meant to store AI-specific data:
scriptmem variable is meant for strings, and the
scriptmem_float is for float value. For example,
scriptmem_float was used a generic timer (for waiting). On the other hand,
scriptmem was used to store how many times the AI has heard a specific trigger by checking and appending keywords onto the string.
Another important thing about AI is the switch between scripted AI and ‘nominal’ AI. Nominal AI is one that is already pre-programmed in C2 where if there are no scripts directing the AI, it will follow a certain logic (which also depends on the type of AI it is). Two things needed to happen. First the AI needed to know which AI it was allowed to switch to, and this was put in a C2 variable called
ai. For example, one agent was assigned
ai=script,see. This allowed the agent to switch to ‘script’ mode, but also allow state changes to occur when the C2 ‘see player’ trigger was fired. There was a ‘hear player’ trigger that existed, but because this was not included in the variable, the agent did not respond to hearing, only seeing, and only triggers involving scripts. This
ai variable assignment is first done in Tiled, and then propagated to the agent during TMX load.
In addition to the
ai variable, the agent had to be put into an FSM state called “script” when it is in scripted AI mode, which allows the system to distinguish which part of the AI sequence it is in. The C2 events which constitute the AI for that agent must consider other FSM states, like “idle”, which is often the ending state after a move.
AI is a bigger topic and I will delve into it more when needed.
I find, more and more, that groups are quite useful not only in organising and commenting, but allows simpler conditional actions to be done in-game. The only example I have is the deactivation of user input if a particular state is on-going. This makes it trivial to block input rather than having check conditions of state all through the user input event.
SLG movement cost
SLG movement cost functions can actually be quite simple. At first I thought it needed to accommodate many aspects, but in the end, despite the relatively complex requirement of the test AI, pathfinding, at most, needed only to query the LOS status of a tile. Impassability was bypassed by excluding impassable tiles from the MBoard, making pathfinding simpler and, I think, faster.
It’s also probably best to name SLG movement cost functions with the following convention: <char> <purpose> path. Eg: “npc evade path”, or “npc attack path”, whereby in the “npc evade path” the NPC avoids LOS, and “npc attack path” does not avoid LOS at all.
Orthogonal and Isometric measurements
I’ve researched and learned a lot of about how to transfer orthogonal measurements to isometric values. The positional values were simple enough, but the real progress was in computing angles.
Here is a list of important considerations when dealing with isometric stuff:
- Converting a C2 object angle (orthogonal space) to an isometric angle (OrthoAngle2IsoAngle). This is used to draw a line in isometric view if that line’s angle was the same as in orthogonal view.
- Converting an angle depicted in isometric view to orthogonal space (IsoAngle2OrthoAngle). This is used to determine what an angle would like when viewed from top-down. So when you measure the angle between two points, it’s not truly the angle when viewed in orthogonal space because the isometric view is skewing things. IsoAngle2OrthoAngle allows the reverse computation so that, for example, LOS could be determined for a particular point.
- Converting orthogonal XY positions to logical XY (OXY2LXY). There is no Board function that allows this mainly because this is a peculiarity of the way Tiled positions objects of the Board. The positioning of objects is written in orthgonal space, but when Rex’s SquareTx projection is set to isometric, then all measurements become isometric. Thus this function is needed for this lack.
- Movement Board and Graphics Board versions of OXY2LXY. This is required because SquareTx for each Board is different, and thus the logical positions will yield a different location.
- Computing isometric distance to orthogonal distance. This measures two points in isometric space and gives out the distance as though you were looking from above. This is useful in determining the distance between foreground and background objects. This uses a SquareTx as a point of reference for the width/height ratio, but can use the MBoard or GBoard, because they are assumed to have the same ratio.
- Computing snap angle (Angle2SnapeAngle). Looks at the object’s angle, and finds the nearest angle to snap to (assuming 8 directions). This is required so that the proper animation is set.
- Converting MBoard logical positions to GBoard logical positions and vice-versa (MLXY2GLXY, GLXY2MLXY). This is very important as it is able to relate the MBoard to the GBoard. Because the MBoard has smaller cell sizes, querying the logical positions of the MBoard using bigger GBoard logical positions will always yield the top-left cell of the MBoard.
- Convert GridMove direction to C2 angle (GetGridMoveDirection). The GridMove values are quite different. This function converts it for use with other things, like animation, or other function related to facing, which use the C2 angle, or snap angle.
The last part of this post is about LOS. I’ve already wrote about some aspects of this. But the main path of the research lay in the following:
- A Line-of-sight behaviour is applied to the player.
- The player’s facing angle is taken as orthogonal.
- An LOS field-of-view is defined (eg 90 degrees) for the player.
- At a given angle (facing_direction), left-side and right-side fov lines are drawn based on the defined fov (90 degrees). Note that these lines are virtually drawn orthogonally.
- The left and right lines are then converted to isometric angles.
- Because the left and right lines have been transformed, the difference between these two angles have changed. This new difference is the new LOS field-of-view.
- The center between these two lines is the LOS center line. The player’s LOS is rotated towards the center.
- With the new LOS field-of-view, and a new center, this corresponds to an isometric LOS based off a 90-degree LOS when viewed orthogonally.
- The facing_direction mentioned above bears special mention. When a player clicks on tile in-game, he is actually picking with a view that he is viewing it in isometric view. Therefore, the facing_direction is an isometric angle, which must be converted to an orthogonal angle. It is only then that the left and right fov lines can be properly oriented, because they, in their turn, will be converted back to isometric after the computation is done.
What needs to be explored
ZSorting seems to take a lot of cpu time (~50%), and I’m wondering whether there is a way I can optimise this. So far, the best solution I’ve come up with is to use On GridMove as a condition for sorting. But I think the most ideal way is to localise the sorting around the areas where movement is taking place.