Android Application Development Tutorial - 182 - 3D Rotation Video Lecture

what's up guys welcome to your hundred
and eighty second Android tutorial for
the new Boston and just quickly to show
you guys what era is having for this one
I said six three one and it's supposed
to be six three two so if you guys
followed along exactly like me and
jumped off the same bridge well that's
the that's err you want to fix and we're
going to do in today's tutorials a
sycamore to our object so we can kind of
see that it is three-dimensional and
it's going to be pretty simple so we're
going to go into our GL our renderer
class whether you guys create a new
renderer for our cube render or not
we're just going to add some rotation
and how we do this is pretty simple
we're just going to say GL again
relating to the GL ten object that we're
going to pass in we're going to say GL
rotate and we're going to use the F for
float and the first parameter here is
the angle so we're just going to say I
don't know whatever angle you guys want
and then we're going to say which axis
is it effects so so if you guys wanted
to the rotation to affect the x-axis we
can just put like one and if we don't
want it to affect affect the I axis
we're going to put zero and the z-axis
will also have it affect that as well or
actually let's just do zero as well for
that and there we go we had some
rotation and let's just copy this and
paste it as well and this time we're
going to add like a third rotation to
the z-axis something like that just so
you guys know you can break it up as
well put one here and let's just run it
see how it looks
and we're also and I'm also going to
show you guys another just quick tip
that you can actually relate to the
actual time it was what you're going to
want to do when you're working with like
velocities and such you don't want to
just have it run off the system because
your CPU might be slowing down and all
that good stuff so you actually want to
you want to run it off of real time
instead of CPU time so
hopefully we can run this application
it's kind of taking a while here and the
emulator crashed awesome
so hopefully that wasn't our fault but I
don't think it was alright it's about
time and also we're probably only going
to do a few more OpenGL tutorials like
said I'll probably show you how to
texture that triangle and then we're
going to get into just some easy stuff
for the most part so as you can see it's
it's rotated a little bit in the
x-direction and a little bit more on the
Y or the Z direction so you know that's
cool but we want it to rotate
consistently so we're going to do is
we're going to rotate according to time
this is a little method or a trick that
I learned from basically the Google
developer page again I'd highly suggest
by now you guys can probably read
through some of that code and learn a
lot through the sample code that they
have to offer but what we're going to do
is we're going to set up a variable
called time and it's going to be a long
I'm just going to say a long time like
that and we're just going to refer to
the system clock so again just system
clock if I believe we did something like
this with our stopwatch application and
we're just going to say dot update time
and we're going to get the modulus of
this so we're going to divide it by
4,000 el and then we're going to say
float angle we're going to set this
equal to point zero zero nine F x times
the nth value of time so there we go now
we have our angle setup which is going
to change according to the actual time I
guess talking about when you guys
develop games you want to refer to your
game according to real time instead of
system time because again the CPU can
slow down
and you know your game will play very
well so you'd rather refer to something
that actually relates to real time
something like this this setup here and
all we're going to do for angles we're
just going to say angle angle here as
well which I which I guess we can just
say
you know of one or or two so now spin a
little bit faster in the Z direction as
well so let's just run it and hopefully
we get this to work doesn't crash our
emulator again and again so that's
pretty much it for this tutorial guys as
you can see add some rotation which mean
which is being updated by real time so
there you go that's pretty much your
introduction for the 3d opengl stuff I
know it went kind of slow but hopefully
you guys understand OpenGL a little bit
more and then we're going to get in
texturing that triangle and then
probably something else and then we're
just going to wrap everything up add
some ads to our application and put it
on the marketplace so that's what you
guys have to look forward to and I'll
see you guys in the next tutorial hope
you have a good one see you later