For Loop Problems.
Blitz3D Forums/Blitz3D Programming/For Loop Problems.
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| Hey, I'm having a problem with some enemy types that I use a For Loop to control. This is in a 2D game by the way. I first created the Enemy Type. Then I generated about 100 of them. Then I use a For Loop to control them all. What I need to do, is to check each enemy, to see if he has overlapped with any of the other enemies, and then do stuff if they have overlapped. How do I check to see if several enemies of the same type, in the same For loop, have overlapped with each other? I tried creating a different set of types that move along with the enemies, and then I could check to se if the enemies overlapped with Those, but it doesn't Work out so well :( A For loop with over 100 guys, running inside Another For loop with over 100 guys, really slows things down ba- -dly. Thanks if anyone can answer this, its really driving me nuts, lol. |
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well, the double loop is the only straight forward way.. especially if you are doing pixel perfect checking. but you dont need two types
For s.ship = each ship
for check.ship=each ship
if checkoverlap(s.ship,check.ship)=true then dosomthing()
next
next
If you dont care about pixel perfect then you could simply make a world psuedo grid. Lets call it World(1000,1000) where each space represents the size of a character.. for this example lets say characters are 10x10 units big. Then each psuedo grid can have a value that represents how many entities are within it. When a ship moves you check the grid to see if other entities are already there if so.. they collided. heres some pseudo code, for the pseudo grid Const GridSize=10 Dim WorldGrid(1000,1000,3) ; the 3 is there because we have 3 collision types.. so 3 cells per grid Type Ship Field entity Field collision_type% Field OldGridx%,OldGridy% End Type Function Shiphasmoved(s.ship) ;the ship is moving, lets make sure we flag the world grid with our location NewGridx=Int(Floor(EntityX(s\ent)/gridsize)) NewGridy=Int(Floor(EntityY(s\ent)/gridsize)) ;see if we are now in a new grid If newgridx<>s\oldgridx Or newgridy<>s\oldgridy Then ;we moved.. so remove our flag from old grid space WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)=WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)-1 ;ideally if you do things right per entity, this should never drop below 0.. If WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)<0 Then WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)=0 ;ok we removed old location.. put in new one s\oldgridx=newgridx s\oldgridy=newgridy WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)=WorldGrid(s\oldgridx,s\oldgridy,s\collision_type)+1 End Function Function TestCollision(s.ship) ;now check to see if anythine else is there If WorldGrid(s\oldgridx,s\oldgridy,1)<>0 Then ;do somthing if you want to act on colliding with object type 1 EndIf If WorldGrid(s\oldgridx,s\oldgridy,2)<>0 Then ;do somthing if you want to act on colliding with object type 2 EndIf If WorldGrid(s\oldgridx,s\oldgridy,3)<>0 Then ;do somthing if you want to act on colliding with object type 3 EndIf End Function |
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| Wow thanks! That should work perfectly. I didn't know that I could use the same type in a double For loop like that. I like the grid idea as well. I'll try both, and see which works faster. Because I am aiming for speed in this game, and have to execute things as quickly as possible. Thanks for your help! WERDNA |
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| Well the more ships you have the faster the psuedo grid will be by comparison, as you can do it per entity not a loop within a loop You could tweak it, to get collisions a little more accurate.. simply by making the grid size say 1/3rd the size of the ship but having the ship effect (or place itself in ) a 3x3 block of grid spaces.. wich would be slightly larger than the ship in actual space used, but would work on smaller steps (more accurate) |
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