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homogenization question

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4 comments, last by davidadams 22 years, 11 months ago
This is a math question. For example , x'' = x*c1/z y'' = y*c2/z z'' = c3z how to get the matrix M . V'' = M * V | x'' | V'' = | y'' | | z'' | and | x | V = | y | | z |
daividadms
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quote: Original post by davidadams
This is a math question.


Post it to the Math and Physics forum.

quote:
For example ,
x'' = x*c1/z
y'' = y*c2/z
z'' = c3z
how to get the matrix M .
V'' = M * V
| x'' |
V'' = | y'' |
| z'' |

and
| x |
V = | y |
| z |


Your notation is a little unclear, but I gather that you want to construct the transformation matrix M. Given that
    |m11 m12 m13|M = |m21 m22 m23|    |m31 m32 m33| 

and
        |m11*x + m12*y + m13*z|M * V = |m21*x + m22*y + m23*z|        |m31*x + m32*y + m33*z|(column-major multiplication) 

your desired matrix is:
    |c1/z 0    0 |M = |0    c2/z 0 |    |0    0    c3| 


This can be tricky to construct since the matrix is dependent upon the multiplicand.
M is a constant matrix , it can not contains variable z .
daividadms
Then you logically have no solution. You could multiply by another matrix which did the z division for you, but there''s no way a single matrix M will yield the desired result if it cannot contain z. Sorry.


People who can''t do shit, talk.
-Dwight Yorke
quote: Original post by davidadams
This is a math question.
For example ,
x'' = x*c1/z
y'' = y*c2/z
z'' = c3z
how to get the matrix M .
V'' = M * V
| x'' |
V'' = | y'' |
| z'' |

and
| x |
V = | y |
| z |


Of course this doesn''t belong in this particular
forum, right....?




Ferretman

ferretman@gameai.com
www.gameai.com

From the High Mountains of Colorado

Ferretman
ferretman@gameai.com
From the High Mountains of Colorado
GameAI.Com

Since I cannot move this thread (being a roving moderator) then all I can do is reply with some questions to try and assist with solving the problem.

Firstly, is this transformation from (x,y,z) to (x'',y'',z'') intended to be a coordinate transformation or a time update?

That is, if it were a time update then it might look something like

x(t+1) = x(t) + c1/z(t)
y(t+1) = y(t) + c2/z(t)
z(t+1) = c3z(t)

Either way of course, for your set of equations there is no constant matrix such that

V'' = M*V

where V = [x y z]T

because your variables form nonlinear functions of each other

Perhaps you could elaborate on the context of the problem so that we could help a little more?

Cheers,

Tim

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