Matrix numbers??

R2005 Vlisp:

Can anyone point me to infomation on lisp matrixes?

The help files has some examples, but they really don't explain what all the numbers are or what they affect.

scaling matrix: scale by 10 at point (2,2,0)
10.0 0.0 0.0 -18.0
0.0 10.0 0.0 -18.0
0.0 0.0 10.0 0.0
0.0 0.0 0.0 1.0

I'm trying to understand all these figures.

TIA

Bill

 

Ok, while I can't provide a point-by-point breakdown, I hope that this
explanation will give some idea as to its purpose.

What you're referring to is a scalar matrix, there are also translation
matrices. Think of these as mathematical references to translate between 2
'worlds'. A prime example that I imagine you're familiar with is the
(trans) function in LISP that will translate (translation matrix) a point
between coordinate systems. Basically, LISP has some pre-defined matrices
for the different translations that will interpret a World coordinate system
into the User coordinate system and vice-versa. There are values for
translating the point and rotation.

Now, where this may apply in the construction of a routine is the need to
transpose (translate matrix) an object or otherwise drawn in the 2D plane
onto a 3D surface that is turned on a different coordinate plane and/or
rotated. If you're attempting something like this, you're writing a rather
complex routine and I wish you the best of luck.

Your example is not much more than the complicated version of scaling by 10.
You could type in 'scale', and put 10 as your factor, or you could calculate
against the matrix - same result.

It's been way too long since I've done matrix math to give you a quality
explanation.

Hope I didn't just confuse you and make you want to go mix a stiff drink.

the numbers are or what they affect.

 

Thanks Jason,
My goal is to translate some flat 2d polygons from one plane to another. No doubt will be a long term project.
It appears that some of these numbers affect the xyz, size and extrusion direction. Just looking for a breakdown.

Bill

 

Bill,
See R2005 Help..Index, 'transformation matrices..transforming objects..Display.
Shows a Table of 'Transformation matrix configuration'.

Bob

 

Bill,
Look at these links:

http://bishopw.loni.ucla.edu/AIR5/homogenous.html

http://tinyurl.com/2hvx9

I have a feeling that the numbers represent the matrix
multiplication of [scaling matrix] * [translation matrix]

 

Thanks Doug,

BTW:
What is the difference between x and x' or y and y'
I see this but don't understand.

Bill

 

(x,y,z) to (x', y', z')

original -> transformed

or

source -> destination

 

I'm curious, how are you approaching it?

Depending on method, could be possible to simply use the native (trans)
function in LISP, though the the process for any complex polygons could be
as complicated as working it out with (trans). Though! You would save
yourself the headache of having to learn and understand matrices, not to
mention you'd have to first figure out the matrices, then write a
translation matrix that will interpolate between two user planes.

man, i'm getting a headache just imagining the process :/ time for me to
mix a stiff one

No doubt will be a long term project.

direction. Just looking for a breakdown.

 

Bill,

The following link helped me get a handle on matrices. Vladimir Nesterovsky talks
about how to construct and use them. There's also a couple utility functions, mxv and
mxm, which I found useful.

Link: http://tinyurl.com/3cfcb

Joe Burke

numbers are or what they affect.

 

From: Jason Wilder
I'm approaching it like I don't know anything about it.
But really just as a personal educational experience.

Trans functioning points may be included but does vary a little from transforming a 2d plane as far as I know.
If nothing else I should learn something and maybe even come up with some new ideas.

Vlisp has opened some new doors as far as matrixes are concerned. I've yet to check them all out.

Bill