Parabola issue

[jeo77]

Okay, heres the deal, I'm working on an artillery style game, with two tanks on a random terrain, which shoot (turn based) at each other. The player chooses the angle (left and right arrows) and the power (up and down arrows) of the shot. However, to simulate gravity, im using parabolas, which is very hard to do, considering i've only learned how to graph parabolas using the vertex in math. I have a good chunk of it down pat, but it seems the parabola always starts at the wrong height (sometimes even off the screen). I was wondering if anyone could give me a hand with this.

(Please note the messyness, im just learning )

code:

cls setscreen ("Graphics: 1000;500") %TERRAIN GENERATOR var upordown, y1, yfill : int randint (y1, 100, 150) for x1 : 1 .. 1000     randint (upordown, 1, 2)     yfill := y1     loop         drawdot (x1, yfill, black)         yfill := yfill - 1         exit when yfill = 0     end loop     if upordown = 1 then         y1 := y1 + 1     else         y1 := y1 - 1     end if end for %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %PLAYER PERAMITERS var p1health, p2health : int var p1angle, p2angle : real var p1power, p2power : int var p1locationy, p1locationx, p2locationy, p2locationx : int p1power := 200 p2power := 200 p1angle := 0.0001 p2angle := 0.005 %PLAYER 1 LOCATION GENERATOR randint (p1locationx, 10, 450) p1locationy := 400 loop     if whatdotcolor (p1locationx, p1locationy) not= black then         p1locationy := p1locationy - 2     end if     exit when whatdotcolor (p1locationx, p1locationy) = black end loop %TANK LOCATION var player1tank : int player1tank := Pic.FileNew ("orange_tank.jpg") Pic.Draw (player1tank, p1locationx, p1locationy, picCopy) Pic.Free (player1tank) %TURRET LOCATION var player1turretx, player1turrety : int player1turretx := p1locationx + 25 player1turrety := p1locationy + 22 drawline (p1locationx + 15, p1locationy + 12, player1turretx, player1turrety, black) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %PLAYER 2 LOCATION GENERATOR randint (p2locationx, 460, 690) p2locationy := 400 loop     if whatdotcolor (p2locationx, p2locationy) not= black then         p2locationy := p2locationy - 2     end if     exit when whatdotcolor (p2locationx, p2locationy) = black end loop %TANK LOCATION var player2tank : int player2tank := Pic.FileNew ("blue_tank.jpg") Pic.Draw (player2tank, p2locationx, p2locationy, picCopy) Pic.Free (player2tank) %TURRET LOCATION var player2turretx, player2turrety : int player2turretx := p2locationx + 25 player2turrety := p2locationy + 22 drawline (p2locationx + 15, p2locationy + 12, player2turretx, player2turrety, black) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %PLAYER 1 MOVE var p1prepare : string (1) var p1shotx2, p1shoty2 : int var newplayer1turrety, newplayer2turrrety : int newplayer1turrety := -10 %%%ANGLE%%% %MOVE TURRET TO THE LEFT process turretmoveleft     loop         getch (p1prepare)         if ord (p1prepare) = 203 then             drawline (p1locationx + 15, p1locationy + 12, player1turretx, player1turrety, white)     %ERASE OLD TURRET             if player1turretx >= p1locationx + 15 then                 player1turretx := player1turretx - 2                 player1turrety := player1turrety + 1                 p1angle := p1angle - 0.0005                 newplayer1turrety := newplayer1turrety - 5             else                 player1turretx := player1turretx + 2                 player1turrety := player1turrety - 1                 p1angle := p1angle + 0.0005                 newplayer1turrety := newplayer1turrety + 5             end if             drawline (p1locationx + 15, p1locationy + 12, player1turretx, player1turrety, black)     %DRAW TURRET WITH NEW INFO         end if     end loop end turretmoveleft %MOVE TURRET TO THE RIGHT process turretmoveright     loop         getch (p1prepare)         if ord (p1prepare) = 205 then             drawline (p1locationx + 15, p1locationy + 12, player1turretx, player1turrety, white)     %ERASE OLD TURRET             if player1turretx >= p1locationx + 15 then                 player1turretx := player1turretx + 2                 player1turrety := player1turrety - 1                 p1angle := p1angle + 0.0005                 newplayer1turrety := newplayer1turrety + 5             elsif player1turretx >= p1locationx + 21 then                 player1turretx := player1turretx - 2                 player1turrety := player1turrety + 1                 p1angle := p1angle - 0.0005                 newplayer1turrety := newplayer1turrety - 5             else                 player1turretx := player1turretx - 2                 player1turrety := player1turrety + 1                 newplayer1turrety := newplayer1turrety - 5             end if             drawline (p1locationx + 15, p1locationy + 12, player1turretx, player1turrety, black)     %DRAW TURRET WITH NEW INFO         end if     end loop end turretmoveright fork turretmoveleft fork turretmoveright delay (1000) %GRAVITY/SHOT process p1fire     var p1x, p1y : real     var p1x1, p1y1 : int     p1x := player1turretx     %fire the shot     loop         p1x1 := player1turretx + 20         p1y1 := player1turrety         p1y := p1angle * p1x * (p1power - p1x) + player1turrety         p1x := p1x + 1         p1x1 := floor (p1x)         p1y1 := floor (p1y)         drawdot (p1x1, p1y1, blue)         delay (12)         exit when whatdotcolor (p1x1 + 1, p1y1) not= white     end loop     %explosion     for a : 1 .. 50         drawfilloval (p1x1, p1y1, a, a, white)         delay (10)     end for end p1fire fork p1fire

[Cervantes]

Why "simulate" gravity using parabolas when you can easily apply the force of gravity to your shell. On the surface of Earth, gravity accelerates us down. We'll say, for your game, that it accelerates everything down at one pixel per (loop execution)^2. (Standard units of acceleration are m/s^2.)

code:

View.Set ("offscreenonly") var shell :     record         x, y, vx, vy : real     end record     := init (0, 0, 5, 15) loop     shell.vy -= 0.3         % Accelerate the shell down by reducing its velocity at a constant rate     shell.x += shell.vx     % Apply the shell's horiz. velocity to its horiz. position     shell.y += shell.vy     % Apply the shell's vertical velocity to its vertical position     cls     Draw.FillOval (round (shell.x), round (shell.y), 5, 5, black)     View.Update     delay (10) end loop

[jeo77]

wow, thanks, thats much easier, and is working perfectly!
2 Bits for you!

[Geminias]

what do bits do?

[MysticVegeta]

Frankly, I don't see a purpose but here is always a link to tell you what they do

[Cervantes]

Ah, jeo77 catches on fast!

But there's one thing you didn't realize. Moderator's bits are locked at 1000 (set back to 1000 after each post). I'll give you your 2 bits back. Thanks is all I need.

Also, the wiki is a good source of information.

[Geminias]

lol @ hacker dan. Well heck, remind me not to get bits in the future. That's kind of cruel, having a "currency" but being unable to do anything with it.

You should have to contribute to get bits awarded to you, and you shouldn't be allowed to post your own topics and ask questions unless you have bits. That would be a way to force people to share their knowledge, else get none in return. But, that's just my crazy-nobodylikes kind of thoughts.

[Cervantes]

Geminias wrote:

You should have to contribute to get bits awarded to you, and you shouldn't be allowed to post your own topics and ask questions unless you have bits. That would be a way to force people to share their knowledge, else get none in return. But, that's just my crazy-nobodylikes kind of thoughts.

So, you are only allowed to post topics if you have bits. So, you have to reply to topics before you can post your own topics. Think what that would do to the people who come here looking for help: they wouldn't be able to post, and probably never would. CompSci.ca growth plummets.

Now, let's stop spamming, shall we?

[jeo77]

Thanks again Cervantes, but now I got another question for ya.
So far my whole program involves processes, but my 'partner' for this project made a menu screen, with a GUI, which has the whole game fitting into one process. Now normally I'd rip the menu to shreds and do it different () but it's a 2-person project, and this is about all the guy has done (cause he's not really good at it, I don't blame him). So I need to incorperate it into the overall program... Here's the menu part (took sum stuff out, cause it has nothin to do with the actuall programming it self...

code:

import GUI %START THE GAME procedure startgame end startgame %HOW TO PLAY procedure controlls     colorback (black)     cls     color (green)     put "How To Play"     delay (5000) end controlls %MAIN MENU View.Set ("graphics:1000;500,nobuttonbar") var menuscreen : int menuscreen := Pic.FileNew ("menu_screen.jpg") Pic.Draw (menuscreen, 0, 0, picCopy) Pic.Free (menuscreen) var draw : int := GUI.CreateButtonFull (100, 10, 0, "Go To War",     startgame, 0, '^D', true) var draw2 : int := GUI.CreateButtonFull (500, 10, 0, "Controlls",     controlls, 0, '^D', true) var quitBtn : int := GUI.CreateButton (900, 10, 0, "Quit", GUI.Quit) loop     exit when GUI.ProcessEvent end loop

The problem is that you can't put a process in a process, so what should I do?

[Cervantes]

First, you should read about why you should avoid processes.

Second, you should consider the possibility of changing the code a bit so as to avoid processes.

Third, if you must keep processes, you don't need to define a process within the definition of another. You need to call a process from another. Can you not fork the play_game process from the menu process, if the appropriate conditions are met?

I assume the menu contains a "Play Game" type button. Since you're using Turing's GUI, that button requires an action procedure. That procedure should contain the following line (in some manifestation or another):

code:

fork play_game