C++ Allegro 5 Made Easy Tutorial 29 - Rotating the Screen [Camera Effects] Video Lecture | Allegro: A Complete Guide - Game Development

hello everybody and welcome to your
twenty ninth level 5 tutorial so in this
tutorial we're going to be expanding our
last tutorial and we're going to be
learning on how to rotate the camera
okay so uh we're gonna have to say
welcome back to our degrees variable so
we're going to create it again and if
you don't know what I'm talking about if
you watch my bitmaps effects video or a
tutorial 27 and you'll know what I'm
talking about so we have our degrees in
there and if we press W we increase the
degrees you press down we lower the
degrees this time we're not going to be
rotating an image where we're going to
be rotating the camera and we can rotate
it around an image if you want to it
really depends on where we rotate it so
what I have right here what the function
used is called the rotate al rotate
transform and then it takes the that
transform a trying to transform and the
radians that you're trying to transform
from so the 3.1415 / 180 that will
convert it from degrees to radians so if
we were to run this program ah when we
see one when it rotates we see that I
rotates around the origin so it rotates
around the coordinate 0 0 if we notice
that the problem is that oh no the thing
is that like some people might really
like that but some people might want it
to rotate around an object or they want
to rotate around the center of the
screen or something else like that right
so but we need to have the opposition
and where we rotate it from so what we
need to do is we need to or where
whatever we want to rotate we have to
take that we need to translate it to the
origin position right so we need to make
that the origin position so it can
rotate around that position and we need
to translate everything back so it looks
as though everything is okay in our
world and then it will rotate from that
position right so in order to set the
position when we rotate from we need to
translate it to that origin position set
that and then translate everything back
so if you don't understand what I'm
talking about then you should understand
what I'm saying after so if we do L
translate transform and we have our
camera before uh we we did that it was
negative Cameron position etc etc this
time we want to rotate around the center
of the screen ok so what we're going to
do is we're going to take uh we're going
to take negative screen width divided by
two and we're going to take negative
screen height divided by two okay so
basically the coordinates so the origin
position is going on the origin position
is going to be the center of our the
center of the screen okay so we
translate it we do so we're going to be
drawing our world that negative 400
negative 300 and therefore the center of
the screen is going to end up at the
coordinates 0 0 on our screen right in
our world or in our screen or whatever
right but in reality it is our objects
are it's just our objects are translated
or whatever so once we do that if we
were to run this program what we see
what we see is that our world is moved
or Rose translated but if we notice if
when we rotate it it's still the origin
position is over here so it's rotating
around that position as you can see
right so everything starts rotation from
that origin position that we specified
the so the problem is that we set our
world towards the left but we need to
convert it back into our regular screen
coordinator positions so we can do is do
a lil translate transform and we do and
camera and then we would do our positive
screen width divided by two and screen
height divided by two so we just
translate it back into the original
position other was that
so then if you rotate it now we notice
that it starts rotating from the center
of the screen right so everything it
rotates from the origin so we set the
position where you want to rotate now
the problem with this is that it doesn't
incorporate screen scrolling at all with
it so so you want to incorporate our
screen scrolling with this or what we
could do was we just set our counter
position as we say a negative counter
position 0 plus the screen our weight /
to right and we do that same for the y
coordinate so we say camera position 1
plus and we have to have negative
captain position and if you run this
program no matter where we go our screen
is going to scroll and then when we
rotate it it's going to scroll a crop
arm according to the center of the
screen right but in this case it would
be if we're a player and we wanna we
have a player Center it would be make
more sense to rotate around the player
so around the center of the players so
what we're going to do is going to do
minus we're going to say that first
we're going to transform it to negative
a negative x plus 16 which is going to
be get the center of the sprite and we
say negative y plus 16 and then instead
of adding y to it so whatever you
subtract from here that's what you add
to it so in this case we say camera-
counter position plus X plus 16 sorry
and then over here we say plus y plus 16
so then if we run this program again no
matter where our player is it rotates
around the player so then if we're if
we're scrolling whatever we're scrolling
across the screen no matter where the
player is we're going to be rotating
around the player position so that is
essentially it for this program I hope
you enjoyed
thanks for watching and oh maybe I
should move it out more so you guys can
see more well yeah that is it for this
tutorial thanks for watching hope you
enjoyed it and by