Hate Your Job?   

Do You Hate Your Job?
If You Are Like Me And REALLY Hate Your Job, You Can Do What I have Done And
Tell All About Your Company At A Great And CHEAP New Site Called
Dont Work For These . Com

http://www.dontworkforthese.com
This Site Has Chat Rooms,
A Joke Section,
A Great Story Section Where You Can Tell All The Funny Or Stupid Things That
Happen Or Have Happened To You During Your Working Day.
Work Forums For You To Ask And Reply To Questions
And Do Not Forget You Can Tell All About Your Terrible Treatment You Endure
While Trying To Make A Living.
Best Of All They DO NOT Want Your Credit Card Details In Order To Join.
You Pay Through PayPal™ And That Means You Know It's Safe.*
They Only Charge £2.50 (or Your Currency Equivalent) For Everything.
You Do NOT Pay For Anything Else For A Whole Year And Have Full Access To
Everything.
Guaranteed.
No Hidden Charges, No Hidden Extras. Membership For A Whole Year. Not A
Monthly Fee In Sight. So Check Out
Dont Work For These . Com
http://www.dontworkforthese.com  Today.

date: Sun, 29 Jun 2008 09:57:01 GMT   author:   unknown

Rotation of an object shrinks it...   

Hi,

I'm basically making a 2D engine, I've started with DirectX few months
ago, so I'm still learning alot of stuff while working with it...I
mean, don't get angry with my questions xD

My situation - I'm using orthogonal projection in my application, it's
set with this code:

D3DXMatrixOrthoLH(&m_matProj, width, height, 0.2f, 20.0f);

, where width and height are those from my window's size. When I
rotate an object 90 degrees, it kinda shrinks it's width with visibly
20-30%, I can't tell exactly how much and what is causing it, I know I
see it. I'm not an expert in math, but I think I correctly ordered the
calculation of the scaling, rotation and translation matrixes, as I
somewhere read it should be S-R-T. So I'm just guessing it's not that
code that causes this problem, I must be missing something. This is my
code that's calculates the world matrix for every object:

	float fOffX, fOffY, fScaleX, fScaleY;
	fScaleX = (float)m_nObjectWidth /m_nScreenWidth;
	fScaleY = (float)m_nObjectHeight / m_nScreenHeight;


	fOffX = ( 0 + (float) m_nObjectPosLeft / m_nScreenWidth  ) - 0.5;
	fOffY = ( 0 - (float) m_nObjectPosTop  / m_nScreenHeight ) + 0.5;


	D3DXMatrixTranslation(&m_PositionMatrix, fOffX, fOffY, 1);
	D3DXMatrixScaling(&m_ScalingMatrix, fScaleX, fScaleY,  0); // scale
the quad with same aspect ratio

	// rotation
	D3DXMatrixRotationYawPitchRoll(&m_RotateMatrix, m_fObjectRotationX,
m_fObjectRotationY, m_fObjectRotationZ);

	m_WorldMatrix = m_ScalingMatrix * m_RotateMatrix  * m_PositionMatrix;


I hope someone knows why do I get shrinking when rotating.

Thanks,
Pencheff

date: Sun, 29 Jun 2008 15:05:25 -0700 (PDT)   author:   Pencheff

Re: Rotation of an object shrinks it...   

[Please do not mail me a copy of your followup]

Pencheff  spake the secret code
 thusly:

>My situation - I'm using orthogonal projection in my application, it's
>set with this code:
>
>D3DXMatrixOrthoLH(&m_matProj, width, height, 0.2f, 20.0f);
>
>, where width and height are those from my window's size. When I
>rotate an object 90 degrees, it kinda shrinks it's width with visibly
>20-30%, [...]

Is your window square?
-- 
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
      <http://www.xmission.com/~legalize/book/download/index.html>

        Legalize Adulthood! <http://blogs.xmission.com/legalize/>

date: Wed, 02 Jul 2008 13:13:24 -0700   author:   legalize+ (Richard [Microsoft Direct3D MVP])