Pygame (Python Game Development) Tutorial - 70 - Shell Collision Video Lecture | Pygame (Python Game Development): Create Awesome Games - Front-End Programming

everyone what is going on welcome to
another hugging tutorial video in this
video we're going to be moving towards
finding the solution to how we know when
there has been a collision of our shell
basically right now where the collision
will be on the ground so whenever that
shall crashes through the ground
where is the x and y of that so there's
a couple of things that we could do but
for example I just fired the show let me
bring it up here and you'll see that the
shell never actually the height again is
600 the show never actually hit 600 and
I'll see that the difference between
here and here we've had a 23 pixels
movement along the Y and along the X we
had 8 what 8 pixels can't add up 8 turns
out 8 isn't too much but like the
difference between it could be up to 10
pixels or 15 pixels or even 20 pixels
and we want to know exactly where along
the you know why did that show really
hit and so there's a few things that we
can do about that we're trying to see if
since we called that quit before the
shell actually hits the ground it's like
this one is actually pretty good at hit
599 I don't think we'll ever see a 600
just because we cancel it out before we
ever get there but as you can see we get
like 588 and all kinds of other numbers
possibly before we actually get our
answers so anyway what can we do to find
out where that crossover occurred so
what we're going to do is we're going to
come down into the fire shell function
and here's where we asked if the shell
is greater than display height if it is
fire equals false now so what I want to
do is within here what we can do is we
can say let's just make some space we
can say we can print
and we can print last show and we can
say last show was what was it and then
we'll just say starting show zero comma
starting starting gel one so we know
what the last show was and then what we
can do is we can basically use cross
multiplication to find within decent
reason where that shell was so we won't
necessarily get the arc but we'll get
basically the straight line between
those two those two points right and
within a pretty good degree certainly a
better degree than what we have like
using like bullish shell location we can
find out where that show would have hit
if it actually did hit so what we can
say is we can say hit underscore x
equals the integer of starting shell 0
times display underscore height and then
and really this is all one thing here
that divided by starting show one and
then we would say hey underscore Y easy
enough is the int of display underscore
height so what's happening there
let me well let's go ahead and print out
impact as well so we'll say print impact
: hit honors 4x hit underscore Y let's
save it and run that and let's go ahead
we'll take this will fire the show boom
bring this up the last shell location
that we knew about was actually 317 612
so our best estimation for the true
impact if that shell was allowed to
you would have been 310 and 600 so how
do how do we actually get that you saw
the function but I do just want to
exemplify how we do that
it's just cross multiplication so we are
basically asking the question x over 600
so this is the X 600 is the Y right so X
is width this is your height and then we
say equals and the last shell was 317
and 612 so equals 3 wow that's a really
bad 3 317 over 612 beautiful so so then
what we do is we use cross
multiplication here and we say basically
612 x equals 600 times 317 and that's
really the equation and what this boils
down to is 600 times 317 divided by 612
that's basically what x equals so that's
what we're doing in our function so when
we come back to this we're saying
starting shell zero times the display
height divided by starting shot 1 and
that's we're doing cross multiplication
but that's how we convert it into one
liner algorithm for Python so that's how
we can calculate where this shell
actually impacted on on the you know
screen
so anyways now that we have an impact we
can then we can then build where we
actually might you know make an
explosion where we can say okay this is
where the shell exploded so that's what
we have to look forward to in the coming
video so stay tuned for that