Trigonometry Help - Missle Tracking

[RedRogueXIII]

Hello, I am having problems getting the projectile to track properly.
It is based on angles, finding the angle going to the target then shifting its direction as appropriate to hit it.
But :
-the projectile seems to not work properly when going straight up, down, left or right.
- the projectile turns the longer way to get to the angle, say if it was at 356 and the target angle was 4 then it goes back down clockwise instead of counter-clockwise
- When it goes left it just plain messes up, i have no explanation or do not understand why it does this ?

Help would be very much appreciated. (there are no images)

::: NOTE : Press Space to launch one missle, the target is always the mouse.

code:

View.Set ("graphics, offscreenonly") var misslex, missley, missleAngle, missleSpeed, mx, my, mb, clsize, timerchk, savedTime : int clsize := 10 var shootFlag : boolean := false var chars : array char of boolean timerchk := 0 savedTime := 0 missleAngle := 90 missleSpeed := 10 proc crosshair     drawoval (mx, my, clsize div 2, clsize div 2, green)     drawline (mx, my + clsize div 4, mx, my + clsize, green)     drawline (mx, my - clsize div 4, mx, my - clsize, green)     drawline (mx - clsize div 4, my, mx - clsize, my, green)     drawline (mx + clsize div 4, my, mx + clsize, my, green)     drawbox (mx - clsize div 4, my - clsize div 4, mx + clsize div 4, my + clsize div 4, green) end crosshair proc missleGuidanceSystem (targetx, targety, misslex, missley, timerchk, timesave, angle : int) %********The problems lie in this process of code.     if timerchk >= savedTime + 10 then % change amount for faster reacting missle.         savedTime := timerchk         drawline (misslex, missley, targetx, targety, green)         var ang, difx, dify : real         % Find the difference between the missle and the target         difx := (misslex - targetx)         dify := (missley - targety)         if difx = 0 then             difx := 0.00000001         end if         ang := angle         % Find the Angle wanted         if dify < 0 and difx > 0 then             ang := arctand (dify / difx)             if ang < 0 then                 ang := 180 + ang             end if         elsif dify > 0 and difx < 0 then             ang := arctand (dify / difx)             if ang < 0 then                 ang := 360 + ang             end if         elsif dify < 0 and difx < 0 then             ang := arctand (dify / difx) - 180             if ang < 0 then                 ang := 180 + ang             end if         elsif dify > 0 and difx > 0 then             ang := arctand (dify / difx) + 180             if ang < 0 then                 ang := 360 + ang             end if         end if         % move the missle's angle closer to the 'wanted' angle         if ang = 0 or ang = 360 then             ang := 0             if missleAngle > 135 and missleAngle < 180 then                 missleAngle -= 5             elsif missleAngle > 185 and missleAngle < 235 then                 missleAngle += 5             end if         elsif missleAngle > 235 and ang < 45 or missleAngle > 270 and ang < 90 then             missleAngle += 5         elsif missleAngle < 90 and ang > 270 or missleAngle < 45 and ang > 235 then             missleAngle -= 5         elsif missleAngle < ang then             missleAngle += 5             if missleAngle > 360 then                 missleAngle -= 360             end if         elsif missleAngle > ang then             missleAngle -= 5             if missleAngle < 0 then                 missleAngle += 360             end if         end if         locate (2, 1)         put misslex - targetx, " x ", missley - targety, " y ", ang : 0 : 0, " angle " ..     end if end missleGuidanceSystem proc move (x, y, distance, angle : int) % Moves the ship depending on the angle.     var ang : real := intreal (angle)     var h, w, m, b : real     h := distance * sind (ang)     w := distance * cosd (ang)     misslex := x + round (w)     missley := y + round (h) end move proc collision % Handles Collision     if Math.Distance (misslex, missley, mx, my) <= 10 then         for decreasing i : 4 .. 1             drawfilloval (mx, my, i * 5, i * 5, 40 + i)         end for         shootFlag := false     end if end collision proc launch % Press space to creat a missle     Input.KeyDown (chars)     if chars (' ') and shootFlag = false then         shootFlag := true         misslex := maxx div 2         missley := 30         savedTime := Time.Elapsed     end if end launch proc drawMissle     drawfilloval (misslex, missley, 3, 3, red) end drawMissle loop     timerchk := Time.Elapsed     mousewhere (mx, my, mb)     crosshair     launch     if shootFlag = true then         drawMissle         missleGuidanceSystem (mx, my, misslex, missley, timerchk, savedTime, missleAngle)         move (misslex, missley, missleSpeed, missleAngle)         collision     end if     locate (1, 1)     put shootFlag, " ", timerchk, " ", savedTime, " ", missleAngle, "degrees angle " ..     drawfilloval (maxx div 2, 0, 20, 20, blue)     View.Update     cls     delay (10) end loop % PROBLEMS MISSLE WILL NOT GO OVER 360 TO GET A VALUE LESS THAN 90 % COMPASS DIRECTIONS ALSO MESSED UP.

[MysticVegeta]

why not use an if structure to say if difference is > 180 then use counter clockwise else use clockwise i.e. if angle > 180, angle is 360 - angle?
PS: I am a complete newbie to trig, i only know grade 10 trig, so I might have a stupid answer

[TokenHerbz]

i took grade 11 hardcore trig, but that was 2 years ago :S

Anyways, i forgot it all, and i can't run your program cause my turing dosn't have math.distance thing...

anyways, i recomend going into the compsci.ca irc channel, and ask a person named """"Ultrahex""""

He helped me with some trig, but, don't bug him, if its a no its a no, or you'll get banned.

[HellblazerX]

for the portion of code that looks for the angle between the missle and the target, I would suggest you use this piece of code:

code:

%****************************CALCULATE GUN ANGLE*********************             hyp := Math.Distance (mx, my, maxx div 2, maxy div 2 - 7)             width := mx - maxx div 2             if hyp = 0 then                 hyp := 0.001             end if             player.gunangle := round (arccosd (width / hyp))             if my < maxy div 2 - 7 then                 player.gunangle := round ((180 - player.gunangle) + 180)             end if

Me and my partner made this about a year ago for our final project, so I don't remember much about it. But i do remember that arctand gave us a lot of troubles, so we just used arccosd instead.

As for finding the quickest way to turn, try this:

code:

var difang : int := ang - missleAngle if difang > 0 and difang < 180 then     missleAngle += 5 elsif difang > 0 and difang >= 180 then     missleAngle -= 5 elsif difang < 0 and difang < -180 then     missleAngle -= 5 elsif difang < 0 and difang >= -180 then     missleAngle += 5 end if if missleAngle < 0 then     missleAngle += 360 elsif missleAngle > 360 then     missleAngle -= 360 end if

basically, with this code, it calculates the difference between the desired angle and the missle's angle. If the difference is positive, and less than 180, then you should go counterclockwise, which is adding angles, but if it is less than 180, then you should go clockwise, which is subtracting angles. if the difference is negative and less then -180, then you should go clockwise, and counterclockwise if it is greater than -180. The last portion is to wrap around the angle so you don't go greater than 360 or less than 0.

As for the projectile not working properly when turned at 90, 180, 270 and 360 degrees, add 0.0001 to the angle you're working with. Because tan of 180 and 360 gives 0, which is a problem when dividing by that, and tan of 90 and 270 degrees is undefined, which is even more of a problem.

[RedRogueXIII]

BUMP- Im justing bumping this to show my solution in case anyone has the same problem. (BTW: Added a graphical smoke trail to the missle, to increase performance just comment it out in the main loop)

code:

View.Set ("graphics, offscreenonly") var misslex, missley, missleAngle, missleSpeed, missleTurnSpeed, mx, my, mb, clsize, timerchk, savedTime : int clsize := 10 var smokecount, smokeMin, smokeMax : int var smokex, smokey, savTime : flexible array 0 .. 0 of int smokecount := 0 smokeMin := 1 smokeMax := 1 var shootFlag : boolean := false var chars : array char of boolean timerchk := 0 savedTime := 0 missleAngle := 90 missleSpeed := 7 missleTurnSpeed := 5 function speedAdjustments (startAngle, endAngle : int) : int     % Changes how fast the missle will turn     var value1, value2, low : int := 0     if endAngle > startAngle then         value1 := abs (startAngle + (360 - endAngle))     elsif endAngle < startAngle then         value1 := abs (startAngle - endAngle)     end if     if endAngle > startAngle then         value2 := abs (startAngle - endAngle)     elsif endAngle < startAngle then         value2 := abs ((360 - startAngle) + endAngle)     end if     if startAngle >= endAngle - 7 and startAngle <= endAngle + 7 then         result missleSpeed     end if     if min (value1, value2) = value1 then         low := value1     elsif min (value1, value2) = value2 then         low := value2     end if     /* Find the lowest difference then change      the speed according to how big the difference is for more precise targeting*/     if low > 0 and low < 45 then         result 1     elsif low > 45 and low < 90 then         result 5     elsif low > 90 and low < 135 then         result 10         %elsif low > 135 and low < 180 then         %result 15 %     elsif low > 170 then         result 15     end if     result 5 % This is the base missleTurning Speed end speedAdjustments function upOrDown (startAngle, endAngle : int) : int     % Finds if the missle's angle will be added, subtracted or stay the same.     var value1, value2 : int := 0     var move : int := 0     % 1 adds 2 minuses 3 says stay on course     if endAngle > startAngle then         value1 := abs (startAngle + (360 - endAngle))     elsif endAngle < startAngle then         value1 := abs (startAngle - endAngle)     end if     if endAngle > startAngle then         value2 := abs (startAngle - endAngle)     elsif endAngle < startAngle then         value2 := abs ((360 - startAngle) + endAngle)     end if     % 1 adds 2 minuses 3 says stay on course     if min (value1, value2) = value1 then         move := 1     elsif min (value1, value2) = value2 then         move := 2     end if     if startAngle >= endAngle - 5 and startAngle <= endAngle + 5 then         move := 3     end if     result move end upOrDown proc crosshair     % Draws a crosshair     drawoval (mx, my, clsize div 2, clsize div 2, green)     drawline (mx, my + clsize div 4, mx, my + clsize, green)     drawline (mx, my - clsize div 4, mx, my - clsize, green)     drawline (mx - clsize div 4, my, mx - clsize, my, green)     drawline (mx + clsize div 4, my, mx + clsize, my, green)     drawbox (mx - clsize div 4, my - clsize div 4, mx + clsize div 4, my + clsize div 4, green) end crosshair proc missleGuidanceSystem (targetx, targety, misslex, missley, timerchk, timesave, angle : int)     %********The problems lie in this process of code.     if timerchk >= savedTime + 10 then     % change amount for faster reacting missle.         savedTime := timerchk         drawline (misslex, missley, targetx, targety, green)         var ang, difx, dify, ratio : real         % Find the difference between the missle and the target         difx := (misslex - targetx)         dify := (missley - targety)         if difx not= 0 then             ratio := dify / difx         else             ratio := dify / 0.001         end if         ang := arctand (abs (ratio))         if difx < 0 then             ang := 180 - ang         end if         if dify < 0 then             ang := 360 - ang         end if         missleTurnSpeed := speedAdjustments (angle, round (ang))         % STEER TEH EXPLOSIVE WARHEAD :P         if upOrDown (angle, round (ang)) = 3 then         elsif upOrDown (angle, round (ang)) = 2 then             missleAngle -= missleTurnSpeed         elsif upOrDown (angle, round (ang)) = 1 then             missleAngle += missleTurnSpeed         end if         if missleAngle > 360 then             missleAngle := 0         elsif missleAngle < 0 then             missleAngle := 360         end if     end if end missleGuidanceSystem proc move (x, y, distance, angle : int)     % Moves the ship depending on the angle.     var ang : real := intreal (angle)     var h, w, m, b : real     h := distance * sind (ang)     w := distance * cosd (ang)     misslex := x + round (w)     missley := y + round (h) end move proc collision     % Handles Collision     if Math.Distance (misslex, missley, mx, my) <= 10 then         for decreasing i : 4 .. 1 % draws a pretty explosion that lasts less than a second :(             drawfilloval (mx, my, i * 5, i * 5, 40 + i)         end for         shootFlag := false     end if end collision proc launch     % Press space to create a missle     Input.KeyDown (chars)     if chars (' ') and shootFlag = false then         shootFlag := true         misslex := maxx div 2         missley := 30         savedTime := Time.Elapsed     end if end launch proc smoke     % Create some nice graphical smoke to follow your missle around     var r : int := Rand.Int (5, 7) %(smokeMin*10, smokeMax * 10) Save for faster computers :(     if timerchk mod 1000 >= 0 then         smokecount += r         new smokex, smokecount         new smokey, smokecount         new savTime, smokecount         for i : smokecount - r + 1 .. smokecount             smokex (i) := misslex             smokey (i) := missley             savTime (i) := timerchk         end for     end if     if smokecount > 0 then         for i : 1 .. smokecount - 1             if savTime (i) + 3000 <= timerchk or smokex (i) < 0 or smokey (i) < 0 or smokex (i) > maxx or smokey (i) > maxy then                 for k : i .. smokecount - 1                     smokex (k) := smokex (k + 1)                     smokey (k) := smokey (k + 1)                     savTime (k) := savTime (k + 1)                 end for                 smokecount -= 1             end if         end for         for i : 1 .. smokecount             r := Rand.Int (-1, 1)             smokex (i) := smokex (i) + r             r := Rand.Int (-1, 1)             smokey (i) := smokey (i) + r             drawdot (smokex (i), smokey (i), grey)         end for     end if end smoke proc drawMissle     drawfilloval (misslex, missley, 3, 3, red)     %drawarc (misslex, missley, 20, 20, 0, missleAngle, green) end drawMissle loop     timerchk := Time.Elapsed     mousewhere (mx, my, mb)     crosshair     launch     if shootFlag = true then         drawMissle         missleGuidanceSystem (mx, my, misslex, missley, timerchk, savedTime, missleAngle)         collision         move (misslex, missley, missleSpeed, missleAngle)         smoke     end if     locate (1, 1)     put shootFlag, " ", timerchk, " ", savedTime, " ", missleAngle, "degrees angle " ..     drawfilloval (maxx div 2, 0, 20, 20, blue)     View.Update     cls     delay (10) end loop

[NikG]

Wow!
That smoke trail is awesome, but a little buggy.

What are your plans for this (i.e. what kind of game is this, or are you just experimenting?)

[RedRogueXIII]

Well i made it for a game I am/was working on, but now further into it, I doubt if Turing will be able to handle parts of it. Anyways the game is supposed to be similar to the popular Evasive manuvers game, eg topdown ship dog-fighting, but I don't know if I'll finish it in Turing.

[codemage]

Still goes a bit buggy for some angles. If you get it just right, the missile keeps heading in the opposite direction indefinitely.

Out of curiosity, what things are you planning to do that allegedly can't be done in Turing?

[RedRogueXIII]

The parts I believe that Turing can't handle at the same time are the scrolling background which i intended to make a map editor for, a pre-set point walls systems, multiple graphics(like being able to handle 10 or more ships on screen + accomodating missles/ lasers/bombs , proper ai navigation around the walls and then i planned to try online multiplayer over the sending and receiving of commands to a server program...
and yea its the missles are still buggy, got to fix that...