[jME Tutorial 2-3] Introduction to shaders in the jMonkeyEngine Video Lecture | jMonkeyEngine Shader Tutorial: A Complete Tutorial - Game Development

okay before I start talking about
shaders I thought I'd give you a bit of
a history lesson before OpenGL too but
namely OpenGL 1.5 vertex and fragment
shaders didn't exist there was a
so-called fixed pipeline you would send
stuff to OpenGL they would do what it
had to do and then give you the result
back and so this fits function FZ
pipeline you can call the api slide the
j monkey engine go through some
primitive processing some lighting
rasterizing fog and all this other stuff
until get to the frame buffer then this
is what depicts what's going to appear
on your screen so your screen will in
essence keep reading from the frame
buffer probably 60 times a second
depending on the screen refresh rate so
if your program your graphics card isn't
refreshing the frame buffer more than 60
times a second you're going to have
frames are going to repeat themselves on
your screen and you can have bad frame
rate so but prior or after OpenGL 1.5
came OpenGL to which introduced vertex
and fragment shaders this gave the
computer program are a lot more control
at the GPU low-level scale so what
happens now because after je manque
engine has sent all the mesh data to the
graphics card you can now play around
some of the vertices
and then after your vertex shader has
run it will then be sent to the fragment
shader which is responsible for the
pixels that appear on your screen so
then you can start adjusting some of
them and then it goes through the rest
of the stuff until it's back to the
frame buffer so yes and now you've got a
lot more control about what you send to
the frame buffer hence what appears on
your screen it's a few of the diagrams I
can show you this is on the gym and
kenjan website so this gives you a nice
simple diagram you got a monkey in gym
class sends the mesh data to the vertex
shader computes the world position and
then the pipe position and then what
appears on your screen and screen space
since to the fragment shader and the
pixel can I get sent to the screen and
to get your object to appear where it
should on the screen is gotta go through
a lot of steps first of all within the
object space so if you imagine you
create an object and blender for
instance normally it'll be like at 0 0 0
like in the center of the object space
if you will and then you might say oh
I'm gonna move it four units to the
right after you've been poured it into
the jain monk engine so to get it to
there and them the vertex shader you
have to times it by the world matrix to
get into I coordinates you've got at
times it by the few matrix to get to
work on appear on the screen you've got
tons it by the projection matrix I'll
show you all how to do this later okay
it was ok back to the gym and clean game
and
going to show you what the unshaded
material definition fragment shader on
very actually to look like okay to do
that if you go to your project click the
libraries and folding particular + icon
and then go to the JM e 3 quart jar then
go to comment mad s misc and then you
should find the unshaded at the very
bottom so i'm going to double-click
unshaded op j 3 md and this is what it
looks like you have some material
parameters these are what you pass in
from your jme class so but there's a
color map of light matte color photos to
a separate text cord you've got a glow
map using the globe post processor and
then there's some techniques you define
what GA gosl version you're running on
this is one then you say where your
unshaded vertex and fragment shaders are
located
some wild parameters these are going to
be the world view projection matrix view
matrix normal matrix well do matrix
there's a few others led some defines
which you can then check oh did the
Jamie application supply me a color map
and then you can use this has color map
in your shaders free normal plans let's
just skip that one and glow if you've
ever used a globe post processor this
just allows the unshaded material
definition to be affected by it to a
diploma flow color you're going to open
the unshaded vertex shader as if there's
a few different qualifies you can have
in shaders of lab uniform which is user
specified ones or ones that are passed
from the jain monk application but only
want to be computed once for the whole
shader there's attributes which are
passed by the engine itself the mesh
data mainly the normals the texture
coordinates the vertex positions
tangents stuff like that and there's
also varying with shells example here
which means you're going to pass this
variable to the fragment shader after
you're done within the vertex shader so
if you remember those defines earlier
it's going to check if a color map was
supplied and if it was then it's going
to add another defines will say oh I
need the texture coordinates give them
to me jmontie application so yeah so
basically this line here is you need to
have a GL position in every vertex
shader it's going to
convert the vertices that is given into
the world space where it needs to be
this worldview projection matrix will
make the object up here where it needs
to do on the screen to you take some in
position which is given to you by
General clear engine application it's a
veck 3 so you need to add in another
argument here usually you use one or
give your most consistent results yeah
that's the vitae shading and a fragment
shader
but the main application begins here
it's going to set the color it's just
really white to set all the the vector
for object that's going to have just one
one one one for RGB a red green blue
alpha and then if a color Maps been
defined it's going to more by all those
colors by the column at this sort of
vertex color will do that if you've
specified a color to the mold by notes
and give me a separate texture
coordinate or not for a light map so do
the same again they're just multiply the
colors and then in the end you need a GL
frag color we're just going to say what
this pixel color should be ok I think
that's enough of this and now we will go
into creating our own dye takes and
fragment shader from scratch