C# Xna Made Easy Tutorial 26 - Distance and Circular Collision Video Lecture | C# Game Development: Game Making made Easy (English)

hello everybody and welcome to your next
C sharp racks in a tutorial so in this
tutorial we're going to be learning
about distance collision or as others
like to call it circular collision so
circular cut circular collision or
distance collision uh it's really good
it really it's mainly meant for circles
or it's used a lot but not as much as
bounding box collision a but it can be
really effective when doing collision
with circles and is more precise than
using a bounding boxes for circles I'm
sorry but uh case sorry sir sorry but
yeah so let's get into so basically are
in finding out the distance between our
circles and stuff we use a distance
formula or what I or what is known as
the Pythagorean theorem and the distance
formula derives from the Pythagorean
theorem so let us go to paint for a
while now there's two different methods
I'm going to be showing you how to on
how to do distance collision the one I'm
showing you right now based on
Pythagorean thumb is the most precise
way to do it right in my last in my in
my sfml made easy tutorial series when I
taught this I taught about by doing it
with absolute values and although that
method works well in the collision still
seems precise it isn't precise to the T
it isn't perfectly the right collision
but it could still work I want to be
showing you different methods but this
method is the most precise and if you're
really into position precision and
really want precise collision and don't
want anything or any glitches or bugs or
errors then I suggest you do this method
okay so what is the Pythagorean theorem
well the Pythagorean theorem is when you
have a right triangle you have your
opposite and adjacent side and you have
your hypotenuse and to get the
hypotenuse or it's a squared plus B
squared equals C squared now I have a d
there
the DS representing distance ok so
imagine this is our player and this
point is our enemy or object or whatever
this is this line is a distance between
the two points that is what the
hypotenuse is representing so in order
to find a distance of it we have to find
the we have to know the a squared who
need to know the B squared and then we
have to find the C squared so
essentially in order to find the value
of D or the the side of C or the
distance is going to be equal to C 1 C
is going to be equal to the square root
of a squared plus B squared that is
essentially the formula right so how do
you find the a squared + B squared so
like a for example is going to be the
players exposition subtract the the
enemy's exposition or the 0 is so hard
to type it with a I'm using a laptop but
i am using whatever the touchpad so the
a is going to say that a is going to
represent a represent the players
exposition subtract the enemy's
exposition and the B is going to
represent the players y position
subtract the enemy's y position and you
can do it in any order you could do like
enemy y subtract player why it doesn't
matter because the good thing about
doing to the power of two is that even
if the value is negative or positive
you're going to end up with the same
value for example say y is equal to 10
and enemies y position is equal to 12
10-12 is equal to net negative 2
negative 2 to the power of 2 is equal to
4 few swishes around 12 minus 10 is
equal to 2 and 2 to the power of 2 is
equal to 4 so you're going to end up
with the same number regardless so it
doesn't matter who subtracts to who so
then once you do ace a squared plus B
squared when you find the square root of
a squared plus B squared that's going to
give you the distance between the two
objects between the player and the enemy
so that's essentially what we're going
to do so how are we going to do this
using C sharp so what we're going to do
is we're going to make a double and
we're going to name a distance okay we
remove all the code from the last
tutorial on all the collision call from
the last tutorial so look at this
distance formula right here so we say
that distance is equal to this math dot
square root so we're using the math
class but we're finding the square root
of and we have to use math doubt power
to do to the power of two so this is
this let's say that this is the a so
this is going to be a squared and this
is going to be B squared okay close the
square root of the players position X
subtract the the our enemies exposition
and we're doing it to the power of two
or yeah so we're doing to the power 2
and plus D that players y position
subtract the enemies y position to the
power of 2 and therefore at the after
all these calculations that will give us
the hypotenuse so that will give us a
distance between the player and the
enemy so if we go back to our code all
we have to do is that my image right now
my image is the square right is a square
sprite and this from there's many mainly
for circular collision so normally what
you would do is you would find the
radius of the of the player I guess plus
the radius of the what you're trying to
collide with and then FD if the distance
is less than or equal to the radius of
those two or maybe if you wanted to make
sure this question you can just do less
than so we do distance is less than the
radius of the player plus the radius of
where your clotting with then therefore
there is a collision otherwise there is
no collision since I'm using a square
object and it sends its not rectangular
since the square are then my square is
20 by 20 so basically it's basically a
distance is less than 20 then therefore
there is a collision so if i run this
program
so we get so if i run it and I touch the
enemy you get a collision so no matter
where you touch it you get a collision
so that is the proper way to go about it
but there are alternate methods always
to do stuff filming computer graphics as
you've noted so far like in bounding box
collision bounding box collision isn't
the most precise collision you don't get
a cushion to the T like a in pixel
collision you get perfect collision
that's what they call like pixel perfect
collision because you get the essence of
pixel touches on another pic so that's
supposed to collide with then you get a
collision so therefore the collision is
perfect on the dot we're bounding box
and stuff it's not always the exact type
of collision so if this one if you're
not so keen on being precise you don't
care you're kind of carefree about it
this method it'll still calculate
collision but it might not be as precise
as you want it to be but it with this
method it kind of it might work better
because for a for an example if we run
if we run the program again with the
previous code this code is one precise
and as soon as you touch the edges like
like so there's a collision but most in
most games say you collide with
something are you might it might be a
wall or something you might cry with the
wall and then once you collide with it
it will kind of push your player back or
something because you've collided with
it or so you collide with the enemy or
something and you touch the edge of the
enemy like so right uh and some people
like some games you just don't want the
perfect lives and sometimes you wanted
that the real like the player hovers
over it like it's clear that the players
actually touching the object before you
actually check for collision right and I
don't some games you might want to do
that some games you don't but it's up to
you so let us go back to paint one more
time so let me let me kind of okay let
me drag this up right
here so with the formula we have right
now our formula we have right now what I
was saying before is that no matter how
which order you put this in since you do
to the square root is going to return a
positive numerical value which is what
you want and that is like an absolute
value so instead of doing everything to
the square root etc etc then that you
can always you can you get the kind of
use this formula this formula is not as
precise as the other one but you could
do this if you find the absolute value
of a plus the absolute value of B then
you can equal that to see and then
therefore that will give you
approximately the distance between the
two objects right so the examples right
here so say the end the player y is
equal to 12 and the know the player y is
equal to 10 and the enemy y is equal to
12 10-12 equal to negative 2 but what
the absolute value does is that it the
absolute value returns the positive
value between the two so therefore it
will return negative it will return
positives to instead of negative 2 so
once we do that instead of doing our a
squared plus B squared equals C squared
we can just find the absolute value of a
plus the absolute value of B and that
will give us see it's not the most
precise method of going about it but it
kind of works for example if we if a is
equal to say five and b is equal to five
using the Pythagorean theorem 5 squared
is equal to 25 so 25 plus 25 and if we
find the square root of those so sorry
so if you find the square root of 25 I'm
place interview you find the square root
the square root of 25 is going I know
sorry square root of 50 sorry so we've
25 plus 25 is equal to 50 if you find
the square root of that we get 7.07 so
we get our approximately seven the
distance is approximately seven now if
you use my method
we do the absolute value say we do 5
plus 5 so 5 plus 5 is equal to 10 so
therefore the approximate distance
between them is 10 now in reality you're
only three pixels off so it's not that
big of a difference or and the collision
is still going to seem precise but it
actually isn't that precise if you know
what I mean and if you really need
precise collision or like you need to
say you want to check to see if the
distance between them is 200 pixels away
or something then something happens or
so you have a two-player game where like
two players are playing and you don't
want them to get too far apart from each
other on the screen so you set a minimum
distance they can be apart from each
other then you're going to want to use
the Pythagorean theorem but if you're
not really so concerned about our
position then this this method can could
work for you as well right uh so yeah so
let us get so let's get back into this
this code again so if you want to do
this method that is not so restricted or
whatever or not as precise then you can
use the absolute value so we do is
distance equal to mass dot absolute
value the absolute value of position X
subtract 100 plus the absolute value
between position our player position Y
subtract the enemy's position Y and if
we run this code let's see what we get
if we touch a player there's still
collision so it seems it seems like
right here sees kind of overlapping and
we don't really get a collision but once
you get closer to the enemy you get a
collision so it's not as precise but it
still works so whichever method you
prefer it's up to you but I would prefer
to use the first method so thanks for
watching this hope you enjoyed this and
by