# ISSUE-2241: 1. Introduction - More explanations about the used coordinate system

## used-coord-system

## 1. Introduction - More explanations about the used coordinate system

- State:
- RAISED
- Product:
- Module: Transforms
- Raised by:
- Anthony Grasso
- Opened on:
- 2009-03-22
- Description:
- http://lists.w3.org/Archives/Public/www-svg/2009Mar/0178.html

About 1.1:

I assume x, y, d in [x y d] are scalars (coordinates)

representing a vector (what is an object with direction and

length (euclidian) - is this correct?

How are the matrix elements in the projection matrix related

to the vector and the user coordinate system?

I assume, that the <px>, <py> and <pd> of 2.2 property

are related to the vector [x y d] - correct?

If so, what happens with pd = d = 0 with the matrix element

noted to be '1/-d'?

About 1.2:

Similar question, how is the matrix related to user coordinate,

respectively how transforms a vector in the user coordinate system

with this matrix? (could be similar explained as done in the

SVG specifications)

It is noted, that [a b c d e f g h i j k m] is a vector -

what is the meaning of direction and the length (euclidian)

for this vector? If it has no meaning, it is maybe more a list

of scalars?

Is the d matrix element here related to that with the same

name in the projection matrix? I assume not, if this is true,

maybe the name for the scalar in the projection matrix should

be changed to another unused letter to avoid confusion.

About 1.2.1.-1.2.6.:

I think, it would be simpler to reuse the 'a b c d e f g h i j k m'

from 1.2 in the matrices provided here, if it is a simple scalar.

If these are more complex terms write something like cos(alpha) is ok,

but it should be noted, what alpha is (an angle in degree I assume as

usual in SVG).

Note that the 'a' symbol appears with different meanings in section

1.2 - first as a matrix element, then as an (undefined) angle, as

I assume from the position within the cos - to avoid confusion the

angle should be replaced with another symbol, for example a greek

letter.

In 1.2.3. it is not obvious, what nx, ny, nz or something like

't.nx.nx' might be - is '.' here a symbol for multiplication or some

DOM/ecma-script-style notation separator or something else?

I assume multiplication, because I know those formulars already,

but I think this is not obvious for every reader. - Related Actions Items:
- No related actions
- Related emails:
- minutes, 22 March 2012 SVG WG telcon (from cam@mcc.id.au on 2012-03-23)
- ISSUE-2241 (More explanations about the used coordinate system): 1. Introduction - More explanations about the used coordinate system [Module: Transforms] (from sysbot+tracker@w3.org on 2009-03-22)

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