Hello all,

I am currently working on a 2D RTS game (tiled based and oblique projection). I wanted a way to only draw the entities that are currently on screen, my first instinct was to store the entities in an array, then check through that array, to see if any entities where inside the camera view, and if they where draw them.

However, this will become taxing to do if there is a large amount of units and/or players (enemy), as it would have to sort through the hundreds(ish) of times a second. My second, thought was to store them in a two dimensional array (according to their X and Y values), then use a calculation based of the camera position, to start/stop drawing the entities only in the camera view (this is pretty much the same process I use to draw the map's tiles).

This method has the advantage it would be a lot easier to draw, as I wouldn't need to sort them according to their Y Value (so units could over lap each other (again, oblique projection)). The only real downside is when entities start moving around the map, they would delete each other if they walked through each other(although could be prevented). Also, to me at least, it seems a bit long winded.

Does anyone else have any suggestions/alterations?

Thanks a lot! :)

Hi thanks for your reply, Ill take it on board. You are correct in some areas, and Ill defiantly think about what you said, however...

Most of the time the entities will be doing X,Y or Z off screen, for instance say an enemy is taking 1 damage every two seconds, I will still need to update him and or his AI. therefore simply deleting entities cant be done(?). Any entities that are not onscreen are simply (prob not the right term but) Mathematical, then when the camera rolls around they have a sprite ect. ect.

I don't want to be drawing an entity that isn't visible (whats the point right?), but say there is 200 entities simply polling each one "are you in the camera view?" or "are you active?" every time I render the scene will be a major bottle neck in my game. I guess I was really asking for a better way of doing that.

Sorry for any misunderstanding.

Thanks for the reply, Very helpful.

I guess im one of those people who, doesn't want to bottle neck the system (AT ALL) :)

But seriously thank you about batching the process, once you said it, I remembered an article I read a while ago thinking, "oh Ill have to do that if [this problem] becomes an issue"

Cheers!!

I don't want to be drawing an entity that isn't visible (whats the point right?), but say there is 200 entities simply polling each one "are you in the camera view?" or "are you active?" every time I render the scene will be a major bottle neck in my game. I guess I was really asking for a better way of doing that.

Depends on what kind of a system you are targeting. If you are targeting modern x64 pc with a processor clocked atleast 2ghz you really can't bottleneck the game with an if(unit_x<screenrightborder_x+unitsize&&unit_x>screenleftborder_x-unitsize&&unit_y<screentopborder_y+unitsize&&unit_y>screenbottomborder_y-unitsize) (note border orders may wary depenging on your cordinate system) when your unit count is less than thousands. Infact you can't really optimize it any better than that without falling into the premature optimization whirlpool because you need your untis to "mathematically" be there anyway.

Do you use immidieate mode(drawing each sprite separetely) or are you constructing a vertex buffer object/s to draw your scene? If your target system can support using VBOs then you propably should use them. For example you only would need to construct a VBO for the whole tilemap once at the start and again only if the tilemap changes. Then draw the whole tilemap with a single draw command and let the GPU do the culling.

I am somewhat puzzled over these other guys who keep talking about enemies and bosses and whatnot being close to the player. Last time I checked RTS was for realtime strategy and there were no players in the game. The player was a disembodied viewport in the sky giving orders to all sorts of units. But maeby the RTS genre has changed since five minutes ago.

Long story short. If the game is to be played with a desktop pc or a laptop with under a thousand units you don't need anything more fancier that just checking if the units are on the screen. It'll give you all the optimization you need.

Hey,

Thanks, ill defenitly look into vertex buffers :)

And im not sure, but they could be referring to an RPG, even so, the techniques can be transferred in some instances

Thanks a lot