Android Application Development Tutorial - 171 - OpenGl 2D vertices Video

well it's going on gangsters welcome to
your hundred and seventy first Android
tutorial for the new Boston what we're
gonna get into is actually start
developing some kind of object that we
can display within our opengl class here
I know I told you guys we're gonna
develop a cube but as for now I don't
want to jump into 3d I just want to get
the basic concepts you know developing a
cube is so old-school it's like so
square you know but I want to go into
the basic concepts and just develop a
triangle 2d object and then we'll get
into the 3d since it's pretty much the
same but a little bit different and what
I'm gonna do is just kind of talk about
some of the concepts using blender here
which is a 3d modeling software
animation software all that good stuff
it's free so if you guys are interested
in that
I'd recommend blender if you don't want
to spend the money on like 3d studio max
or anything like that
as you can see here we have a cube which
again we aren't developing we're
developing a square or I'm sorry we're
developing a triangle but with opengl
just some of the concepts that we can do
is we can set the actual camera view so
if this like grey area here is our
phones device we can say hey we want the
camera to be closer the object here so
you know our object appears larger or we
can say or we want our camera way back
here so our object smaller we can also
scale the actual object itself all that
good stuff so that's why we set up kind
of the renderer class that's going to
handle some of those type properties
that we're gonna work with but now let's
just get into the basic concepts of 3d
programming and what what we're gonna
need to know again here's just a cube
and we can rotate around it but that's a
3d object so as for now we're just going
to work with 2d and I'm just going to
switch to like the front view here and
the cube has four vertices the vertices
just basically a point like a point here
a point here a point here and a point
here and then it's connected and filled
and it's shaded all that good stuff what
we're gonna do is we're gonna create a
triangle so we're only going to have
three points and how this works is we
have an X
axis and y axis the x axis goes to the
right is positive to the left is
negative the y axis is positive up and
negative down which we'll get into a
little bit later but just for example
this point right here would be like
negative one and the x-direction comma
positive one and the y direction so
that's what that would be this point so
we're gonna create some vertices in this
tutorial and eclipse but you know that's
just how this is going to work and again
just like for example this point is one
in the X direction and one in the Y
direction then we have one in the X
Direction negative one in the Y
direction etc so let's just jump over to
eclipse hopefully you guys kind
understood why I was trying to explain
there and again I told you guys we're
going to create a triangle so you need
to set up a new class called GL triangle
example or e^x and probably all we're
gonna do in this tutorial set up some of
those vertices or some of those points
that we're gonna connect and fill in
later so how we're gonna do this is
we're gonna create a float array so
we're just gonna say we're gonna say
private because again since we have this
triangle class everything's gonna be for
the most part private and here because
we aren't gonna allow other classes that
change something love these vertices and
stuff like that so we're going to set
these vertices to private and it's going
to be of the type float and we're gonna
save vertices and again we just put
those brackets to say that we're having
a list or a ray of some sort and we do
our opening bracket and let's define the
points that we want to map out and also
we just are going to finish our
statement here and then we're going to
define the points so for example we want
our triangle to have a point of like
here here and then right in the center
up here and we're gonna have to remember
some of these points what we're going to
do is we're going to start at this top
point here and work our way around you
know clockwise like that so let's
develop our first vertice and eclipse
and so again the first or the top part
of the triangle the x-direction is going
to be 0 and we're just going to say F
for float and the first
you know the y-direction is going to be
a positive one because it's going up so
we're just gonna save 1f as well and
then you know we can set up our next
vertice here as well
or like you know 1 or whatever and but
you know it gets kind of confusing when
you look back at your code and all that
stuff
so what we're going to do is we're just
going to hit enter and start a new line
so we know hey yeah we're working with a
2d object with X and the y direction and
that's our first point so you can even
leave a comment here like point one or
something like that or actually this
would be point zero because again in
computers you always start with 0 1 2
etc and then we're going to create our
second point so that's going to be at
the reference 1 in the x-direction and
comma negative 1 and in the y-direction
then we can again leave a comment like
point 1 4 last point it was negative 1
in the X direction and negative 1 in the
Y direction as well now we're just gonna
say point 3 and also we have to I'm
sorry I've got to you know set this
equal to what we want so we're just
gonna set this equal to this bracket
here so yeah so that's why you're
getting those errors because again when
we define an instance of a class we have
to you know set it equal to something so
these are three points again and what I
put point three just messed it up
everywhere and that's point two so again
let's just look at these just quick oh
just a quick tutorial nothing too
complicated but again just to understand
these principles of 3d programming our
first point is zero in the X direction
so and try and show it in blender here
and one in the Y direction so like right
here will be our first point and then
the second point will be one negative
one so it's going to be like one and
then negative one which will be right
here same corner as that square for the
most part and then for third point it's
going to be negative one in the X
Direction negative one in the Y
direction so right here and then what
we're gonna do is we're gonna like you
know connect it and then fill it in and
you know all that good stuff so that's
much it for this tutorial guys just a
basic introduction to 3d programming or
actually I should say 2d programming at
the moment but there we go and I'll
catch you guys in the next tutorial have
a good one