- From: David Woolley <forums@david-woolley.me.uk>
- Date: Tue, 02 Sep 2008 08:26:41 +0100
- To: www-svg@w3.org
Manuel Strehl wrote: > > P(x,y) -> P(x',y'), with > > x' = x + (deviation_left*(1 - x_rel/width) - deviation_right*(x_rel/width)), > y' = y + (deviation_top*(1 - y_rel/height) - > deviation_bottom*(y_rel/height)), It looks to me that the problem with this, compared to a true perspective transform, is that it assumes that a constant delta y in the map corresponds to a constant delta y in the image to be transformed. In a real perspective transform, you will get a smaller transformed delta y in the "distance". The standard 3D homogenous transform matrix can produce a true perspective effect, with z zero on input. For the satellite navigation use case, you would want this, latter, behaviour. Whilst it may not be as easy to use if you are a pure WYSIWYG person, it wouldn't be that difficult for the authoring tool to let you manipulate the image in 3D terms then output the necessary parameters. Applying the transform matrix on the client side only involves multiplications and additions. -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work.
Received on Tuesday, 2 September 2008 07:27:18 UTC