----------------------------------- munt4life Sun May 01, 2011 9:56 am following a path? help please :D! ----------------------------------- Hey i was wondering what i would have to do if im controlling a circle, and there is another circle, how would i get the circle to follow me, i am making a game where theres many obstacles and i was thinking in one part there would be a couple "monsters" chasing me, so depending on where i move they would go towards me as well. Any feedback would be helpful thanks! ----------------------------------- A.J Sun May 01, 2011 12:39 pm RE:following a path? help please :D! ----------------------------------- There are many ways one could implement enemy's chasing you. One naive way to do so is to have the enemies move towards your position at every iteration; to do this, you measure the angle at which the enemy needs to move at, and increase its x and y position (assuming this is a 2D game) accordingly. The downside of this method is that the enemies don't traverse around obstacles (instead they just try going through them). To account for obstacles, however, you need to utilize a path finding algorithm. The one I recommend is the A* ('A star') algorithm (I'll leave it to you to read up on it). If you have any questions regarding it, feel free to ask us here. ----------------------------------- munt4life Sun May 01, 2011 6:05 pm Re: following a path? help please :D! ----------------------------------- im assuming i need trig? ----------------------------------- Insectoid Sun May 01, 2011 6:21 pm RE:following a path? help please :D! ----------------------------------- Yes. It's fairly simple though; since you're only making right triangles, you can get away with sine law. ----------------------------------- DemonWasp Sun May 01, 2011 6:42 pm RE:following a path? help please :D! ----------------------------------- Actually, that particular algorithm doesn't even need sine law (and is faster without it). You just need to remember a few things about similar triangles and Pythagorean theorem. ----------------------------------- Raknarg Sun May 01, 2011 7:36 pm RE:following a path? help please :D! ----------------------------------- or you could use x + cosd (theta) and y + sind (theta) ----------------------------------- munt4life Sun May 01, 2011 8:37 pm Re: following a path? help please :D! ----------------------------------- ok so i tried doing something like theta := arctan((y1-compy)/(x1-compx)) compx+=speedx(cos(theta)) compy+=speedy(sin(theta)) im getting an error on subscripts im pretty sure my math is right what should i fix? ----------------------------------- A.J Sun May 01, 2011 9:02 pm RE:following a path? help please :D! ----------------------------------- I thought you wanted to enemies that are chasing you to avoid obstacles. In which case, the method you are currently attempting to code (i.e. the first approach I described in my previous post) doesn't cut it. ----------------------------------- munt4life Sun May 01, 2011 9:05 pm Re: following a path? help please :D! ----------------------------------- im trying to get the actual moving to work for now then after i will create restrictions i defined all those variables why does turing say speedx and speedy cannot have subscripts. ----------------------------------- A.J Sun May 01, 2011 9:24 pm RE:following a path? help please :D! ----------------------------------- Even if you have the enemies move towards you at every iteration in this fashion, you can't modify it to avoid obstacles as well; the enemies will just keep trying to come towards you even if there's an obstacle in the way. ----------------------------------- munt4life Sun May 01, 2011 9:26 pm Re: following a path? help please :D! ----------------------------------- Could you please tell me why my code isnt working please so i could then move on to such a problem :P ----------------------------------- A.J Sun May 01, 2011 9:44 pm RE:following a path? help please :D! ----------------------------------- I don't see any code here to help you with/. ----------------------------------- munt4life Mon May 02, 2011 5:11 pm Re: following a path? help please :D! ----------------------------------- anyone? ----------------------------------- munt4life Mon May 02, 2011 5:46 pm Re: following a path? help please :D! ----------------------------------- k so now i have this i tried a similar triangles method. var bCoordx := x - compx var bCoordy := y - compy var d : real := Math.Distance (x, y, compx, compy) % computer finds out input position to determine where to move var sx := 10 * bCoordx / d var sy := 10 * bCoordy / d then i have a bunch of stuff in a procedure blah blah so i have drawfillbox (compx, compy, compx + 10, compy + 10, red) how would i make the compx and compy change according to this? im confused please help :D ----------------------------------- Raknarg Mon May 02, 2011 5:53 pm RE:following a path? help please :D! ----------------------------------- Depends on whether or not you want it to avoid obstacles. Is this the case? ----------------------------------- munt4life Mon May 02, 2011 6:20 pm Re: following a path? help please :D! ----------------------------------- it seems im just trying to jget the atleast attraction to work for now :p, perhaps later ill try to add such a feature, for now just the chasing is good without obstacles :P ----------------------------------- Raknarg Mon May 02, 2011 6:59 pm RE:following a path? help please :D! ----------------------------------- ok, well here's a simple explanation: Step 1: Find angle Use arctand ((enemyy - y) / (enemyx - x)). Remember that it changes depending on whether or not the character is above or below the enemy. I would just use something like: if x > enemyx then angle := angle + 180 Step 2: Find vx and vy (the amount x and y change) Easy enough. The formula is: vx := speed * cosd (angle) vy := speed * sind (angle) Then you add those to x and y. Again, that's a simple explanation. Try to use it, and ask if you have more questions about it. Or someone can try and give a better explanation:P ----------------------------------- munt4life Mon May 02, 2011 7:17 pm Re: following a path? help please :D! ----------------------------------- what do you mean add to x and y? ----------------------------------- munt4life Mon May 02, 2011 7:19 pm Re: following a path? help please :D! ----------------------------------- also, yeah i got that much it was just the actual movement of my rectangle( which in this case is the enemy ) that i wanted to move so i got to the part you got too except im not sure what to put into the drawfillbox(????) ----------------------------------- Raknarg Mon May 02, 2011 7:28 pm RE:following a path? help please :D! ----------------------------------- oh... ok You set x and y like so: x := x + round (vx) y:= y + round (vy) Draw.FillBox (x, y, ?, ?, ?) You can set those last three parameters to whatever you need. Also, the vx and vy are positive or negative depending on where they are compared to x and y. Such as: if x < enemyx then vx := -speed * cosd (angle) elsif x > enemyx then vx := speed * cosd (angle) end if ----------------------------------- munt4life Mon May 02, 2011 7:57 pm Re: following a path? help please :D! ----------------------------------- +10 bits thanks alot :D ----------------------------------- munt4life Mon May 02, 2011 8:03 pm Re: following a path? help please :D! ----------------------------------- haha i asctually just got away with the really simple method of drawfillbox (compx, compy, compx + 10, compy + 10, red) if (compx < x) then compx += 5 end if if (compx > x) then compx -= 5 end if if (compy > y) then compy -= 5 end if if (compy < y) then compy += 5 end if ----------------------------------- Raknarg Mon May 02, 2011 8:05 pm RE:following a path? help please :D! ----------------------------------- XD Yeah, that works too. It's only if you want realistic movement. That works fine.