Running in conjunction with acceleration and Input.KeyDown

[Mayb123]

after the ground question, i wanted to incorporate left and right movement so that while the left or right keys are down, the character, at the moment a dot, will move in that direction, building speed up to a maximum velocity. the character must only build speed and/or maintain its velocity until the user releases the key. that's where i'm stuck

code:

setscreen ("graphics:640;480") var key : array char of boolean var ground, vcap, x, y, vx, vy, ax, g, charx, chary, carvx : real const gravity := -0.5 x := 10 y := 10 vx := 1 ax := .8 vy := 5 % g := -0.5 vcap := 10.1 procedure jump     % Makes character jump at the press of the up key.     loop         cls         View.Set ("offscreenonly")         x += vx         y += vy         if round (y)>=10 then         vy += gravity         end if         drawfilloval (round (x), round (y), 2, 2, black)         delay (10)         exit when y = 10         View.Update     end loop end jump procedure crouch % Makes character crouch on the ground. end crouch loop     View.Set ("offscreenonly")     Input.KeyDown (key)     if key (KEY_UP_ARROW) then         jump     elsif key (KEY_DOWN_ARROW) then         crouch         elsif key (KEY_RIGHT_ARROW) then         % movement right here. i think i need a procedure     end if end loop

mod edit: switched quote tags to code

[Mazer]

I would not use procedures in that way. You have a main loop for your program (the one at the bottom); don't stick any loops inside of that, especially to draw/View.Update in them.

As for the velocity thing, you've already got variables to keep track of the velocity's x and y component (check out the tutorials for using records, it'll help make things easier to keep track of).
So what you'll do is check inputs each time you run through the loop (as you are doing now) and if the LEFT arrow is pressed subtract some amount from vx, or add if RIGHT arrow is pressed.

After adding to the velocity, you'll want to subtract as well (let's pretend it's friction). But make sure you're bringing vx toward 0 (ie, if vx < 0, add to it, and if vx > 0, subtract).

Now make sure vx isn't going crazy. If it's getting really close to zero, then that last thing we did could cause it to jump back and forth when the user isn't pressing any keys, so if it's in the range of -SMALL_AMOUNT < vx < SMALL_AMOUNT (say SMALL_AMOUNT is 0.5 or something, whatever works for you), then just make vx 0. Also, if it's in the range of -vcap < vx < vcap, make sure to cap it.

Finally, add vx to x.


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