Re: Angle values for azimuth and elevation
On Aug 4, 3:23pm, T. V. Raman wrote:
> Liam Quinn writes:
> > Next up on my ACSS hit list is angle values for azimuth and elevation.
> > The azimuth property specifies that an angle value be given in the range -
> > 360deg <= x < 360deg. First off, I don't see why -360deg should be
> should be either 0 <= x <= 360
> -180 <= x <= 180
> in either case a total range of 360deg --720 degrees doesn't make sense.
Yup. It was changed from 0 <= x < 360 in response to feedback that
said that this would help with relative values and would be easier
for users (-60 is easier than 300).
Probably better would to allow any values in the property, and then say
" Values in these units may be negative. They should be normalized
to the range 0-360deg by the UA. For example, -10deg and 350deg
> > unclear to me whether other values, such as 370deg or 3.14rad (hmm, we
> > need a way to say pi),
right. Rad is ab obvious unit to use but without being able to say pi/16 or
something I'm not convinced it adds any value.
> You dont want to outlaw 370degress because you want to be able specify
> rendering rules in style sheets of the form
> "increment azimuth by 15 degrees and render yourself"
> to simulate something going around the user with each successive element
> moving 15 degrees along the circle.
> > Similarly, the elevation property specifies an angle value in the range -
> > 90deg to 90deg. Does this mean that 270deg is invalid? Shouldn't this
> > angle value be normalized to the range -90deg to 90deg, contrary to what
> Elevation should be normalized to be within [-90, 90]
> with 90 degrees directly above the users head
> and -90 degrees directly below (North and South poles on a sphere
> centered at the users head)
Precisely. Again, it is probably better to allow any numerical value in the
property and have it be normalized by the UA.
Chris Lilley, W3C [ http://www.w3.org/ ]
Graphics and Fonts Guy The World Wide Web Consortium
http://www.w3.org/people/chris/ INRIA, Projet W3C
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