[jME Tutorial 1-6] Rotations in the jMonkeyEngine (Part 1/2) Video Lecture | jMonkeyEngine Math: An Ultimate Guide - Game Development

join the three axis Y Z and X we can
define rotations around each of these
axis a positive Y rotation positive x
rotation and a positive z rotation so
for example I have a man is facing this
direction he's a happy man
rotating around the z axis by 90 degrees
he will be facing this rotating around
the y axis
taking the initial rotation then he will
be facing in this direction so that's a
y 90-degree rotation direction nan X
rotation
you
find 90 degrees taking the initial
initialization then his feet will be
facing towards the camera
no that's wrong his head will be facing
towards the camera
and let us feel big summer up there and
in JME rotations are defined by court
Iranians quarter four for neons for
something else never X Y Z and W
components court audience can get quite
confusing at first I didn't really
understand them when I first met them
and still don't if I'm honest
and why are they even useful or first
County there are very efficient they
avoid gimbal lock so you don't lose a
degree of freedom if you somehow rotate
wrong wing and they can also be
multiplied together by vectors to give a
new vector rotated by that quaternion
so if I have a vector here at
zero three zero and I've a quarter naeun
defined to rotate minus 45 degrees and
then the new vector will be modified
there 45 degrees
nice choice of color on my part and
photons can be multiplied together it's
not commutative so multiplying
quaternion a by B does not equal the
times a so if I have a quarter nyan or
if I have either character but I'm going
to rotate in the z-axis by minus 90
degrees five a quaternion defined for
that then you'll first of all be facing
this way and then if I multiply but
again and he will then be facing
this way
okay let's go see how to use it some J
multi-engine okay gonna create a new
file ctrl n and my test templates the
coldest rotations and create you spatial
variable going to load our beloved
Sinbad model model Sinbad don't mesh the
X amount and attach it to the root node
I'm gonna add some light from the pallet
one thing you should know is that I've
updated the SDK since last time you'll
find that by going to help check for
updates and then it will check if you
need to update it I suggest you do that
one thing I'm going to do get rid of
these active square brackets and
normalize local what this does is it
changes the variables already inside the
vector 3f object instead of creating a
new one so it just helps a little bit ok
let's shift f6 and see what we've done
okay I'm going to scale Sinbad down a
little bit set local scale not point to
Phi their shift f6 to run it click OK
hey brilliant I'm not going to draw some
arrows to depict the three axis you
create a private method to create one to
assign it's a color
and a direction so you can create a new
arrow with using the arrow class
filtered by using control space I can
find what construct arguments I can put
in or in their direction you're going to
create a new geometry out of the error
and put in the arrow in there and then
going to joseph own to fix the import
and then assign the material so a to
create a new material because each arrow
has to have its own material I'm going
to be changing color stick with the
unshaded material definition you're
going to set the color on it using the
set color method color color and assign
my material to the geometry now I'm
going to create three hours I'm going to
give the z-axis a blue color so color
RGB a blue unit vector constant
going to make the Y color green use the
unit Y vector constant I'm going to
create the x-axis with a bread color
let's see what it looks like okay
okay is there is very small so I'm going
to increase the magnitude of the
dimension well I said four times most of
them to increase the line width of the
arrow comfortable to three in some of
its okay that's a lot better okay going
to now add some key mappings so that we
can rotate our model using that keys on
our keyboard we're going to use the
input manager we use to add mapping it
takes a string and a trigger so I'm just
going to call this X and I'll trigger
them to be a new key trigger and it
takes a input we're going to say key
role shift I to report that then go into
that another one for a y move key
trigger key input Y
at a final one for the z-axis I just
fell on don't do that one wrong it'll be
key X the last thing to do is to add the
key listener but I haven't defined this
yet I'm just going to call it