Hi Amund,
matrix4f.rotY(angle);
does some thing like the following:
public final void rotY(float angle) {
float c = (float)Math.cos(angle);
float s = (float)Math.sin(angle);
m00 = c; m01 = 0.0f; m02 = s; m03 = 0.0f;
m10 = 0.0f; m11 = 1.0f; m12 = 0.0f; m13 = 0.0f;
m20 = -s; m21 = 0.0f; m22 = c; m23 = 0.0f;
m30 = 0.0f; m31 = 0.0f; m32 = 0.0f; m33 = 1.0f;
}
as you can see m03, m13, m23 are reset to zero after this call. I have
attached a little doc that I had written which could
help you get a better understanding of Matrices. I definitely suggest that
you read it, but the general solution would be to
multiply another matrix that is at the origin and has the rotation that you
want into your moonMat.
delta.rotY(5 * PI/ 180);
moonMat.mul(delta);
(see the doc)
Take Care,
--------------------------------------------------------------------------
Syrus Mesdaghi Fullsail Real World Education
3D Gaming instructor Winter Park, FL
[EMAIL PROTECTED] www.fullsail.com
--------------------------------------------------------------------------
----- Original Message -----
From: "Adriano Cavalcanti" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, January 29, 2001 3:24 AM
Subject: Re: [JAVA3D] Question about Rotations
> I have an example about it, but it's in OpenGL - C. If you find
interesting, I
> could send to you. :-)
>
> Zak schrieb:
>
> > I am trying to place an object in its own Locale at (2,2,2). Now I place
a
> > Rotation Interpolator on it and it goes to (0,0,0) and rotates.
> > I want to simulate the moon rotating on its own(in its own Locale), the
> > earth rotating on its own in its own Locale, while in the Universe
Locale.
> > Can I get the RoationInterpolator to Interpoloate on the Locale
Coordinate
> > System?
> >
> > Amund Ricto
> >
> >
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> > To unsubscribe, send email to [EMAIL PROTECTED] and include in the
body
> > of the message "signoff JAVA3D-INTEREST". For general help, send email
to
> > [EMAIL PROTECTED] and include in the body of the message "help".
>
>
===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the
body
> of the message "signoff JAVA3D-INTEREST". For general help, send email to
> [EMAIL PROTECTED] and include in the body of the message "help".
Important concepts that help you understand this documentation:
NOTE: the fields of matrices used in vecMath library are as follow
m00 m01 m02 m03
m10 m11 m12 m13
m20 m21 m22 m23
m30 m31 m32 m33
in other matrix may be implemented based on column-first format instead.
m00 m10 m20 m30
m01 m11 m21 m31
m02 m12 m22 m32
m03 m13 m23 m33
1) Assume that entityMat and delta are pointers to matrix4d:
matrix4d entityMat,
delta;
2) entityMat.setIdentity(); resets the values in entityMat to become 1 0
0 0
0 1
0 0
0 0
1 0
0 0
0 1
the Identity Matrix, represent a matrix that is at the origin (x = 0, y = 0, z
= 0),
has no scale (or skew), and is oriented in such way that its Y axis in up, X
axis to the right,
and z axis along the Normal Vector of the screen (coming out of the screen).
such orientation
is aligned with the Global axis. please note that GameCAD's Global axis are as
follow:
X positive is to the right
Y positive is up
Z positive is Out of screen
where as in Multigen/Creator, the global axis are:
X positive is to the right
Y positive is into the screen
Z positive is up
3) there are 16 fields in a matrix4d object, as I mentioned, the values in an
Identity Matrix
are as follow:
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
each on of these numbers are of type double. in order to change the values in a
matrix directly,
you have to modify the value of one or more variables that exist in the class
matrix4d. the name
of these variables are m01, m02, ... m33. the following diagram show the name
of the variables and
what they represent in the matrix.
1 (m00) 0 (m01) 0 (m02) 0 (m03)
(X.x r&s) (Y.x r&s) (Z.x r&s) (X
position)
0 (m10) 1 (m11) 0 (m12) 0 (m13)
(X.y r&s) (Y.y r&s) (Z.y r&s) (Y
position)
0 (m20) 0 (m21) 1 (m22) 0 (m23)
(X.z r&s) (Y.z r&s) (Z.z r&s) (Z
position)
0 (m30) 0 (m31) 0 (m32) 1 (m33)
(remains 0) (remains 0) (remains 0) (remains
1)
to illustrate the values in an identity matrix lets try to write down the
coordinates
of the tip of each lines below. lets assume the intersection of the three lines to
be
at x=0, y=0, z=0 and that the length of each line is exactly 1. keep in mind that
X
positive is to the right, Y positive is up, and that Z positive is Out of screen
(the
slanted line represents a line coming out of the screen).
*2
|
|
|
/ -----*1
/
*3
*1 : x=1, y=0, z=0 : 1 0 0
*2 : x=0, y=1, z=0 : 0 1 0
*3 : x=0, y=0, z=1 : 0 0 1
as you can see these values are the same as the upper left (3x3) values in an
identity
matrix which represent it's Rotation and Scale (r&s). since we assumed that the
intersection of the three lines are at 0,0,0 , we can place these values to the
right of
the values we have. we can also insert the bottom row that should not be touched.
1 0 0 0(x position, m03)
0 1 0 0(y position, m13)
0 0 1 0(z position, m23)
0 0 0 1 (this row should remain untouched)
lets see how we can manipulate a matrix:
IMPORTANT:
* the order in which you perform your translations and rotation can result in
completely
* different results
* It is very important that you set a matrix to identity when needed. Not paying
attention to
* to this fact can introduce very tough BUGS!
* All vecmath functions are based on radians. In order to convert dx from degrees
to radians
* you can: (dx * PI)/ 180 In order to convert dx from radians to
degrees
* you can: (dx * 180)/ PI where PI = 3.14159
1) Translation:
============
a) Global:
if entityMat is the matrix of the model,
entityMat.m03 += 1 will move the object closer to the right
edge of the monitor
entityMat.m13 += 1 will move the object closer to the top
edge of the monitor
entityMat.m23 += 1 will move the object closer to our eye
b) Local:
if delta is a temporary matrix,
delta.m03 += 1 will move the object 1 unit in it's x-positive
direction
delta.m13 += 1 will move the object 1 unit in it's y-positive
direction
delta.m23 += 1 will move the object 1 unit in it's z-positive
direction
(Note that the above calls were global transformation for delta)
now, we should multiply delta by entityMat in order to cause entityMat to
transform locally
entityMat.mul(delta);
2) Rotation:
=========
* Note that when calling rotX, rotY, and rotZ the fields of the matrix will be
set to
* thoss of an identity matrix. After calling delta.rotX(.f), the delta will
seem to
* be set to identity and then rotated 0.1 radians.
*
* It is very important that you set a matrix to identity when needed. Not
paying attention to
* to this fact can introduce very tough BUGS!
Note: the order by which you multiply two matrices determines whether the
rotation is local or global
a) Global:
delta.rotY(.5);
delta.mul(entityMat);
entityMat.set(delta);
Note: the reason why I did not say entityMat.rotY(.5) is because, the
rotY() method
rotates the matrix BUT resets any other current information in the
matrix. for example,
if you also had rotation around X, it would be reset when you call
rotY()
b) Local:
delta.rotY(.5);
entityMat.mul(delta);
3) Scale:
======
a) Global:
the following block causes the entityMat to Scale up Globally with respect
to Z-axis
entityMat.m20 *= 1.25;
entityMat.m21 *= 1.25;
entityMat.m22 *= 1.25;
the following block causes the entityMat to Scale Down Globally with
respect to X-axis
entityMat.m00 *= 0.8;
entityMat.m01 *= 0.8;
entityMat.m02 *= 0.8;
b) Local:
the following block causes the entityMat to Scale up Locally with respect
to Z-axis:
entityMat.m02 *= 1.25;
entityMat.m12 *= 1.25;
entityMat.m22 *= 1.25;
the following block causes the entityMat to Scale down Locally with respect
to Y-axis:
entityMat.m01 *= 0.8;
entityMat.m11 *= 0.8;
entityMat.m21 *= 0.8;
********************************************************************************************************
if you have any questions/corrections you can e-mail me:
Syrus Mesdaghi
[EMAIL PROTECTED]
********************************************************************************************************
