Firing bullets - angles - help?

[Remm]

OK, if anyone had seen my earlier program in'A question on shooting...', lets just say its alot better now.
However,
I seem to be having problems with multiple angles, like for every move you get a different angle of shot. Having troubles with this.

What ive been trying to use is a rise over run (aka (y2-y1) / (x2 - x1) ) to get the angle of fire and then put it into a y=mx+b thing to get the trajectory of the bullet. However, I dont know what to do with the b.
example:
(This so at any angle x and y, at any angle, can shoot the bullet along that angles line -- will work great for my game ^_^ ... if it works... )

code:

var x, y : int var m : real x := 370 y := 55 Draw.ThickLine (380, 35, x, y, 7, brightred) m := (y - 35) / (x - 380) put m for a : 1 .. 100     Draw.FillOval (x, y, 2, 2, blue)     delay (100)     Draw.FillOval (x, y, 2, 2, white)     x := x + 5 % y  =           m     x  +  b     y := round (m * x) + 800 end for

What should i really put for the 800 (b)?
and is this a good way to be doing this, or is there a easier way? I looked at the one in the flexable arrays example and got all confused.
Thanks,
Remm

[HellblazerX]

If you're going to work with angles, you're going to have to learn trig. It is much easier. See, with your method, you find m, which is the slope not angle. There's a difference. Then, you must substitute a set of points into your equation to determine b, which is the y-intercept. Then you plug into an x-value in to get a y-value, can drawing a line to it. With trig, you can just use the cosine and sine functions to get the x and y values.

[Remm]

uhh, you just confused the crap outta me. Im doing sine / trig n all that stuff in school atm, yet i still don get what ur trying to tell me. Agh, im gunna mingle around in my text book until i find out wth to do, will post what i come up with within a day. Wish me luck.

Remm

[Remm]

sorry for double posting but...
btw, if anyone could help me with getting the formula going in turning, it would be much appriciated. I now see that im not getting anywhere in slope, so i have to do it the trig way. I see the sind and other commands for it, i jus need to know how to get the angle and how to make THAT shoot. Not seeing how to get the x/y values out of it ty again, i'll b trying to find out myself for now.

[TheOneTrueGod]

Angles are not the same thing as slope.

The equation (x2-x1)/(y2-y1) will not get you the angle between two points, only the slope.

You have two options for getting the angle between two points. Use the Math.Angle function included in turing, or create your own Angle function.

In order to use it in turing, you have to know a few things about trig first.
I'll assume you know the basics, such as sin(0) = 0, sin(90) = 1, cos(0) = 1, and cos(90) = 0, and most importantly, WHY.

Allright, with that basic knowledge, you can break up a line segment into two components: its x component, and its y component.

--/ | <-- Y component
/t_|
^
X component

In order to determine the x component, we just take the hypoteneuse (sp?) and multiply it by the cosine of theta (Represented by t in the diagram above.)

The y component is similarily determined by multiplying the hypoteneuse by the sine of theta.

Syntax in turing is as follows:

Radians
sin(angle : real)
cos(angle : real)
tan(angle : real)

Degrees
sind(angle : real)
cosd(angle : real)
tand(angle : real)

Using this information, lets apply it to a very minor program (That I'm not going to bother testing, so if theres any syntax errors, fix them on your own )

code:

const moverate := 3 var mx,my,but : int var x,y : real := 100 loop    mousewhere(mx,my,but)    drawfilloval(round(x),round(y),5,5,black)    x += cosd(Math.Angle(x,y,mx,my)) * moverate    y += sind(Math.Angle(x,y,mx,my)) * moverate    Time.DelaySinceLast(30)    cls end loop

And theres the basics of it

If you want to get into more advanced stuff, there are plenty of good programs in the source code section (Be sure to read the comments before you study the code though, so you can learn which programs aren't good examples )

Anyways, good luck

[Remm]

Ack - my turing doesnt have Math.Angle... ?!!?
So, any ideas on that 'create your own function'? lol -.-
and i KNOW angles arnt same thing as slope, just very poor wording.

Quote:

I'll assume you know the basics, such as sin(0) = 0, sin(90) = 1, cos(0) = 1, and cos(90) = 0, and most importantly, WHY.

uh... yeah... our teacher has yet to tell us why. We jus click the button on calculator an it does stuff - no need to think!
I think i'll ask em on monday.

[TheOneTrueGod]

Allright, Number one, here, you can use my function:

code:

function Angle (x1, y1, x2, y2 : real) : real     %Created by TheOneTrueGod.     var theta : real     if x1 = x2 then         if y2 > y1 then             theta := 90         else             theta := 270         end if     else         theta := arctand ((y1 - y2) / (x1 - x2))         if x2 > x1 then             if y2 > y1 then             else                 theta := 360 + theta             end if         else             theta := 180 + theta         end if     end if     result theta end Angle

Just leave the "created by TheOneTrueGod" line in there, or give me credit somehow and its all good

Anyways, if you plan on doing some programming over the weekend, there are many great tutorials on the web, and there may even be one or two in the [Turing Tutorials] section. Just look around

(And be sure not to use the function unless you know what it does, or else you're not going to understand what your code is doing... not a good thing )

[Cervantes]

Remm wrote:

Ack - my turing doesnt have Math.Angle... ?!!?

I don't think any of them do, unless v4.1 does.

Here's a tutorial by zylum that outlines using trig to move a spaceship. You'll probably find it useful.

[Remm]

Thanks guys, i'll try the thing u gave me god, ran it alone and it didint spam errors so, s'all good. Time to put it to use

[Remm]

Alrighty, thanks to you all, ive gotten it to shoot at least a LITTLE bit properly. I know it still has massive issues, but its a start. I found out what functions are and how to use em per your instructions before using it, since before i was totaly unhinged trying to call up the function. Now, yet another question
How do i shoot more than one bullet at a time? Try turning the SHOOT procedure into a process - thats what i see as a dead end with everything i try. can anyone point me in the right direction as to where i can find it out / any idea for getting the angle thing to work. once i GOT the angle, i was prty blank as what to do next, so i got that strange thing up n running. Dont i have to sine it or somthing?

Heres the code so ye kno what im dealin with:

code:

%============================ var font1 : int var mx, my, mb : int var win1 : int var cannon :     record         x : int         y : int         firex : int         firey : int         firemove : int         angle : real     end record %============================== cannon.x := 380 cannon.y := 73 font1 := Font.New ("Comic Sans MS:30") win1 := Window.Open ("title:Final Gunner;graphics:800;600;position:center;top") Draw.ThickLine (380, 35, cannon.x, cannon.y, 7, brightred) Draw.FillOval (380, 33, 20, 23, black) Draw.Oval (380, 33, 20, 23, brightred) Draw.FillBox (360, 3, 400, 33, black) Draw.FillBox (370, 3, 390, 13, brown) Draw.Line (380, 3, 380, 13, black) Draw.Dot (382, 8, black) Draw.Dot (378, 8, black) Draw.Dot (382, 9, black) Draw.Dot (378, 9, black) Draw.Dot (382, 7, black) Draw.Dot (378, 7, black) Draw.FillBox (365, 23, 395, 18, brightblue) Draw.Line (400, 34, 360, 34, brightred) Draw.FillOval (380, 35, 5, 5, gray) Draw.Line (385, 40, 375, 30, black) Draw.ThickLine (0, 0, maxx, 0, 6, green) View.Set ("offscreenonly") %========================================================================== procedure tower  %look! now its a procedure! ^_^     var towermove : array char of boolean     loop         Draw.ThickLine (380, 35, cannon.x, cannon.y, 7, white)         if (cannon.x > 380) then             Input.KeyDown (towermove)             if towermove (KEY_RIGHT_ARROW) then                 cannon.x := cannon.x + 1                 cannon.y := cannon.y - 1             elsif towermove (KEY_LEFT_ARROW) then                 cannon.x := cannon.x - 1                 cannon.y := cannon.y + 1             end if         elsif (cannon.x < 380) then             Input.KeyDown (towermove)             if towermove (KEY_RIGHT_ARROW) then                 cannon.x := cannon.x + 1                 cannon.y := cannon.y + 1             elsif towermove (KEY_LEFT_ARROW) then                 cannon.x := cannon.x - 1                 cannon.y := cannon.y - 1             end if         elsif (cannon.x = 380) then             Input.KeyDown (towermove)             if towermove (KEY_RIGHT_ARROW) then                 cannon.x := cannon.x + 1                 cannon.y := cannon.y - 1             elsif towermove (KEY_LEFT_ARROW) then                 cannon.x := cannon.x - 1                 cannon.y := cannon.y - 1             end if         end if         if (cannon.x = 420) then             cannon.x := cannon.x - 1             cannon.y := cannon.y + 1         end if         if (cannon.x = 340) then             cannon.x := cannon.x + 1             cannon.y := cannon.y + 1         end if         Draw.ThickLine (380, 35, cannon.x, cannon.y, 7, brightred)         Draw.FillOval (380, 33, 20, 23, black)         Draw.Oval (380, 33, 20, 23, brightred)         Draw.FillBox (360, 3, 400, 33, black)         Draw.FillBox (370, 3, 390, 13, brown)         Draw.Line (380, 3, 380, 13, black)         Draw.Dot (382, 8, black)         Draw.Dot (378, 8, black)         Draw.Dot (382, 9, black)         Draw.Dot (378, 9, black)         Draw.Dot (382, 7, black)         Draw.Dot (378, 7, black)         Draw.FillBox (365, 23, 395, 18, brightblue)         Draw.Line (400, 34, 360, 34, brightred)         Draw.FillOval (380, 35, 5, 5, gray)         Draw.Line (385, 40, 375, 30, black)         View.Update         delay (30)     end loop end tower %=========================================================================== %================================================ Created by TheOneTrueGod function angle (x1, y1, x2, y2 : real) : real     var theta : real     if x1 = x2 then         if y2 > y1 then             theta := 90         else             theta := 270         end if     else         theta := arctand ((y1 - y2) / (x1 - x2))         if x2 > x1 then             if y2 > y1 then             else                 theta := 360 + theta             end if         else             theta := 180 + theta         end if     end if     result theta end angle %===================================================Created by TheOneTrueGod procedure SHOOT     cannon.firemove := 0     cannon.firex := cannon.x     cannon.firey := cannon.y     cannon.angle := angle (380, 35, cannon.firex, cannon.firey)     cannon.angle := cannon.angle / 100     var changex, changey, a, b : real     changex := 10 * (.9 - cannon.angle)     changey := 10     a := 0     b := 0     for x : 1 .. 80         a := a + changex         b := b + changey         Draw.FillOval (cannon.firex + round (a), cannon.firey + round (b), 4, 4, black)         delay (25)         Draw.FillOval (cannon.firex + round (a), cannon.firey + round (b), 4, 4, white)             end for end SHOOT %=========================================================================== process fire     var fire : array char of boolean     loop         Input.KeyDown (fire)         if fire (KEY_TAB) then             SHOOT         end if     end loop end fire %============================================================================ fork fire tower

as you can see i've been steering away processes as much as possible. They are evil.

[Cervantes]

Remm wrote:

How do i shoot more than one bullet at a time? Try turning the SHOOT procedure into a process - thats what i see as a dead end with everything i try.

I'm glad to see you're going to avoid processes. To get this done, you'll need to learn Flexible Arrays. There's an example of just this in that tutorial.

You've got quite a steep learning curve right now, it would seem. Good stuff!

[Remm]

yeah but... every time i look at flexable arrays i get very confused and angry at them. Turings help explination of it is horrid to say the least. I kinda know how to do arrays themselves, i guess i'll try to fortify my understanding of arrays then move on to flexables. Thanks again. some day the bullets will acually be shooting at somthing ^_^