From: SVG Working Group Issue Tracker <sysbot+tracker@w3.org>

Date: Sun, 22 Mar 2009 19:46:47 -0400 (EDT)

To: public-svg-wg@w3.org

Message-Id: <20090322234647.BB9684DD60@crusher.w3.org>

Date: Sun, 22 Mar 2009 19:46:47 -0400 (EDT)

To: public-svg-wg@w3.org

Message-Id: <20090322234647.BB9684DD60@crusher.w3.org>

ISSUE-2241 (More explanations about the used coordinate system): 1. Introduction - More explanations about the used coordinate system [Module: Transforms] http://www.w3.org/Graphics/SVG/WG/track/issues/2241 Raised by: Anthony Grasso On product: Module: Transforms 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.Received on Sunday, 22 March 2009 23:46:57 UTC

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