Revision as of 20:54, 9 August 2012

Problems With Angle Definitions in ODF1.2

Coordinate System

There are two common ways to orientate a Cartesian coordinate system.

mathematical orientation

screen orientation

Only when the orientation is determined, terms like "clockwise" are unambigious. Such orientation rule is missing in ODF 1.2.

Suggestion:

If a rule refers to a two-dimensional coordinate system, a Cartesian coordinate system in screen orientation (see figure ##) is used. The directions "clockwise", "counter clockwise", and the edge descriptions "left", "top", "right" and "button" are accordingly defined as shown in figures [##] to [##].

clockwise rotation of the vector (5 2) to vector (2 5)

The rectangle has the "top-left" vertex (1│2) and the "bottom-right" vertex (6│5).

Angles in Attribute draw:transform

These suggestions are all about section 19.228. (Because of the Wiki markup I skipped the characters < and >).

I suggest to give for each single transformation value an example with reference to the corresponding transformation matrix and illustrate that example .

Original	Problems and Suggestions
	The whole original text is very near to SVG section 7, but a reference is missing.
matrix(a b c d e f), specifies a transformation in the form of a transformation matrix of six values. "The values describe...	Typo: The quotation mark before 'The values' has to be removed. Problem: A standalone translation needs parameter with units. This information is missing here.
rotate(rotate-angle), specifies a rotation by rotate-angle degrees about the origin of the shapes coordinate system.	The orientation of the rotation is missing. I suggest not to use "clockwise" but to define it by an equivalent matrix. Suggestion: Example: The value rotate(30) corresponds to the transformation matrix result of value rotate(30)
scale( sx [ sy ]), specifies a scale operation by sx and sy.	It is not clear, that not only the object is scaled. Suggestion: Example: The value scale(0.2 0.5) corresponds to the transformation matrix result of scale(0.2 0.5). Notice that visually the distances to the axes are scaled too.
skewX(skew-angle), specifies a skew transformation by rotate-angle degrees along the x-axis.	Typo: "rotate-angle" should be "skew-angle". Here is neither clear between which rays the angle is measured, nor what direction is used. Suggestion: Example: The value skewX(25) corresponds to the transformation matrix A rectangle transformed with skewX(25). This transformation is also known as "shear mapping".
skewY(skew-angle), specifies a skew transformation by rotate-angle degrees along the y-axis.	Same as skewX, typo "rotate-angle" and unclear angle. Suggestion: Example: The value skewY(15) corresponds to the transformation matrix A rectangle transformed with skewY(15)
translate( tx [ty]), specifies a translation by tx and ty, where tx and ty are lengths (18.3.18).	In contrast to the other transformations, the parameters need a unit here. Therefore an example is useful. Suggestion: Example: The value translate(2.5cm 1cm) corresponds to the transformation matrix A rectangle transformed with translate(2.5cm 1cm)