W3C home > Mailing lists > Public > www-style@w3.org > August 1997

Re: Angle values for azimuth and elevation

From: Chris Lilley <Chris.Lilley@sophia.inria.fr>
Date: Wed, 6 Aug 1997 17:43:27 +0200 (MET)
Message-Id: <9708061743.ZM18912@grommit.inria.fr>
To: raman@Adobe.COM, Liam Quinn <liam@htmlhelp.com>, www-style@w3.org
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
> or
> -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
    are equivalent."

>  > 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.

Yes.

>  > 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
chris@w3.org                       2004 Rt des Lucioles / BP 93
+33 (0)4 93 65 79 87       06902 Sophia Antipolis Cedex, France
Received on Wednesday, 6 August 1997 11:43:58 GMT

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