GameMaker Studio - Movement Tutorial Part 2 Video Lecture - Game Maker

all right and so now that we've covered
both of those main options in the drag
and drop system what we're going to look
at now is coding these by hand in GML it
really not all that different at all and
you'll see as we go through like how
those drag and drop events translate to
code events and vice versa so if we go
into object playing now and we get rid
of basically everything we already have
so we get rid of all that we get rid of
get rid of stepa then get rid of this
friction by vassal rules no we won't
start with friction actually we'll get
rid of the create event for now as well
so we're just back to just our left and
right events once you learn a little bit
more GML you realize you don't even need
these you can just in the step event use
a piece of code that checks if the left
and right now's not mouse button two
keyboards bones are being pressed but
for now we'll just we'll stick to just
using these left and right infants
because they work fair enough so if we
go to control here and pretty much the
only action you ever need when you're
working with GML is execute code so we
drag that into there so whenever you're
moving left I'm pretty sure we covered
this in the first basic tutorial is to
basically just say X - equals three and
then that in itself is identical to the
very first thing we did in this tutorial
which was jump to position a minus three
relative that is basically an exact
translation of that we're taking our x
coordinates attracting three from it and
then we're ending the line of code of
the semicolon just to tell the game that
that's the end of the line of code so we
hit take there and then we'll do the
same thing over here with write only
we'll do blue X plus C equals three let
me go on and if we go okay run that and
we have exactly what we had to start
with literally no change but it's just
written in code as opposed to written a
drag and drop
so yeah that's literally exactly the
same as the very first thing we did how
we do the next system however in GML is
a little bit more complicated only in
the sense that there's actually a
billion or one ways you could actually
approach this which is part of the
strength of the using code really is you
can do things in a huge number of
different ways to have pretty much the
same outcome that it'll then depending
how you do it it allows you to do other
things the code and so on and so forth
so it really gives you that so the
flexibility and exact control over
exactly how everything in your game
happens so we're going to look at pretty
much the very simplest way of
replicating what we did before in code
which is basically to set our HP to be a
value so our haste key I mean we already
know that like you can tell ng/ml when
you've written a variable that the
object recognizes is sort of one of its
primary sort of variables is because
like if you can see when I'm timing here
see it's just great text there and it's
even come up with the autocorrect there
look variable speed and that that'll
tell us what our speed is but what we
want specifically is to change our H
speed value which is our horizontal
speed so that's a variable the effects
where the object is moved to every frame
so if we set that to three every frame
so HP equals three actually minus three
every frame because that's the left
arrow key and here okay and we go to
write we do the same thing weird equals
three notice how we're setting them
straight to three and minus three so as
you might guess this does pretty much
exactly what we have before only you'll
notice I'm only well you won't notice
because you can't see my keyboard but
I'm only tapping left and right to make
the object moves left and right because
we're just setting our HP and we don't
have our friction setup yet so we're
literally just saying our speed to three
and minus three and then there's no
friction to slow it down on a moment so
it's moving four
so what we do is we go to Advent create
and you already know how to do a through
drag-and-drop but to do this through
through code is very simple you just
type friction and you can see it's
turned red it recognizes the variable
friction we type equals and what did we
have before 0.25 I think so or is it
just not going to nobody will do thank
header five and there we go now we have
the very basics of what we had before
again where we're accelerating what
we're not accelerating actually we're
saying I'll speak to three and then when
we let go of the button we're sliding to
a hole because the friction is reducing
our speed every single frame until it
reaches zero so now what we want to do
is recreate the acceleration effect that
we had before so in order to make your
object accelerate instead of just move
is you can pretty much guess what we
have to do here since instead of when we
move whenever we're holding a left key
setting now hb2 minus three we just H be
minus equals which you know we subtract
from this value what did we use before I
think it was one yeah so we just
subtract one from our hey speed every
time we're holding left tick right in
the same we'll do the same thing over
here so instead of saying on HB 2b 3
which is that hp+ not equals plus plus
equals 1 so now that should accelerate
is 1 in either direction but of course
we need to set our maximum speed
otherwise we'll just go too crazy
velocity super quickly so to set a
maximum speed what we want to do is once
again create our stepper then put an
execute code action into the step event
and we're basically going to do the same
thing we did over here with our
variables which is to check if the speed
is greater than a certain value set the
speed to be that value in whatever
direction it happens to be so if and
then we want to open a pair of brackets
like that and we want to put a car
condition in here so if speed is greater
than
and symbol six so how if statements work
actually while I'm here is we tie once
we type if here that registers that it's
an if statement to the code and then we
put our brackets here and it checked the
game will check to see if the stuff
inside this bracket is true so if our
speed is greater than six it will
perform any actions we put here by the
little bar and then end with semicolon
it will will activate those if we want
to do multiple actions as a result of a
statement what we want to do is use
these sort of sweet little brackets
I can't member the exact term for these
and then we write code in here and then
all of this code we write in here we'll
get performed if this happens to be true
we only need to set one thing to be true
though so we don't actually need these
open brackets all we need to do is put
speed equals six so if speed is greater
than six speed equals six and you can
see how that is exactly the same as the
drag and drop system what we have before
so if we hit take now we go okay should
I less I've forgotten anything drastic
yep leave us with pretty much exactly
what we had before so press left press
right you you slide so if you start
accelerating and then you slide a whole
slew so that's the basics of movement
and left and right the only other thing
we haven't covered which will be quite
important for a top-down shooter is how
to stop because at the moment you could
just move straight out of the screen so
you could you could just keep moving
left forever or move moving right
forever and we want to keep you
contained in this space here so we're
going to look at doing that now so I'm
not actually immediately sure how you
would accomplish this through the
drag-and-drop system and but I know a
very very simple way of doing it through
the code so my general rule of thumb is
if something is very easy to do in code
and can be done in like less than a line
or so like there's no point like using a
complicated sequence of drag-and-drop
actions to do it you know you just
you're wasting time so we're just going
to cover the very simplest way to do
this using the GN
so if you think about what we actually
want to do using GML is we want to make
sure that our x position our x
coordinate of our player object is
basically always inside the playable
space so inside the room so we can
easily do this by saying our X to be
equal to one of two values if you set
type the word min open a bracket what
this does what ninh does it will set our
x corner to be whichever is smallest so
the minimum of however many values we
put into these brackets so if we set our
X to be whichever is smaller its own x
coordinates or the room underscore width
which as you can see has gone red there
which is equal to the width of your room
so imagine if the game was trying to set
your x value to be 700 and the the width
of the room is only 640 it would check
here every frame and it would set your X
to be whichever is smallest out of those
which would be 640 and would keep you
inside the room otherwise if your X is
currently like 500 when you're within
the room it just sets your X to be
itself again
therefore meaning you know you it hasn't
done anything so that all that literally
does it stops you moving out of the
right-hand side of the room now to do
the opposite of that for the the
left-hand side of the room we want to
say x equals max you might have guessed
what this does is sets X to be whichever
is biggest out of however many variables
you put in here I mean you can put more
variables into here as well you could be
laying Y or 5 or anything like that
but obviously we don't need those we
don't we don't put them in but um we
want to set our X to be the maximum of
either whichever is biggest its own
x-coordinate um or 0 so basically if you
would be like a position of minus 20
that's outside of the room so it would
set
so zero would be bigger than X therefore
it would set your x-coordinate to be
zero so on the furthest left of the room
otherwise if your X is 20 and you're
inside the room it would set your X to
be itself again because X is bigger than
a bigger than zero so those are the only
two lines of code you need hopefully I
think if I recall correctly - to keep
you inside the room at pretty much all
times and there we go in and finish this
compiling move left and right as you can
see now we can't point we can't move out
of the room
we're over laughing a little bit because
the origin of our player object is like
directly in the center so that's where
it's tracking our x coordinate to be so
like as you can see it's only tracking
is as being outside the room if our x
coordinate which is like dead in the
center this player object would go over
the edge so if we want to keep ourselves
like fully inside the box like without
like overlapping on the edge we have to
make a small slight change to the Cobras
brain it's very very simple though all
we need to do is basically actually
first of all we need to check how wide
our sprite actually is in the first
place it's 32 by 32 so we go to step and
we go to X we make X the smallest
instead of X in the room with we make it
the smallest out of X and the room with
minus 16 which is half the size of our
ship so like we can't go beyond so the
center of our ship cannot go beyond the
room width minus 16 and we sat down here
instead of 0 we just set 16 okay and
then hopefully what that will do yeah
now we can't we can't move off the edge
of the screen at all and that overall is
more or less everything you need to know
about moving in sort of 2d space with no
real collisions or anything like that so
one bonus sort of extra thing may as
well show you guys now is how to put
basically all of that stuff that we've
done into a
block of code more or less so instead of
having our left and right events we're
basically going to condense ourselves
down to just being in the step event so
we don't need a this stuff anymore we
can delete these events highly and we're
just going to rock our stepper then so
what we need to do is basically replace
those events with some if checks inside
of our player object so all we're going
to do is pipe if keyboard check and then
another open bracket VK left what light
line of code goes there you can use that
one to look up the exact definitions of
these functions and exactly what they do
but all that's doing is basically this
line of code here is exactly a replica
of the event we had here that was the
the keyboard left this is basically that
that event there and instead of the
actions in that event taking place what
will happen is the lines of code we put
inside these brackets will take place so
anything we put in here will happen when
we head left and supposed to as opposed
to the actions we put in place or the
stuff that we put on the other here and
end with a semicolon
so I mean you already know what we did
before is we put eight-speed minus
equals one on the end of that so if I
now copy and paste that again and change
VK to write for H speed 2 plus equals 1
it would basically duplicated what we
had in those life and write events but
kept them all condensed into one one
block of code just so it's easier to
keep track of more than anything so now
all of that line code that we still need
to keep this friction inside our create
event I mean we could set this an off
step event but there's really no point
because we only need to set our friction
once and that's when the object is
created and there would be no point
putting it in a step event because it
would happen every single frame so
there's no need for us to set off
friction again every single frame we're
just we would just be wasting like the
processes time so now that that's done
hopefully there should be absolutely no
difference yeah to what we had before
hold left and right move left and right
and we're golden so that's everything
for like a bonus challenge you could try
now and use everything you've learned
here to make the move up and down
using the up and down arrow keys it's
pretty much yeah you just basically have
to copy and paste everything you've
already seen here but instead of using x
coordinates you use Y coordinates
instead of H speed horizontal speed you
use V speed which is vertical speed
otherwise the code is pretty much
exactly the same the code is almost
exactly the same for making you not move
up with the top and bottom as well so
you could you could have a go at that
next time around we're just going to be
looking at a basic like shooting and all
that kind of stuff and how to how to
create new instances on the on the fly
with code how to shoot bullets and stuff
so I'll see that if anyone has any
questions about anything I've talked
about in this tutorial wants to learn
more about sort of 2d movement babe and
like the drag and drop actions or energy
ml I've gone through or anything like
that please leave a comment so please
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people who would also benefit from this
and otherwise just thanks for watching
and I'll see you guys in the next one