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[Gzz] PEG: concat inverse
From: |
Tuomas Lukka |
Subject: |
[Gzz] PEG: concat inverse |
Date: |
Tue, 5 Aug 2003 11:28:22 +0300 |
User-agent: |
Mutt/1.5.4i |
=============================================================
PEG transform_concatInverse--tjl:
=============================================================
:Author: Tuomas J. Lukka
:Last-Modified: $Date: 2003/08/05 08:26:38 $
:Revision: $Revision: 1.1 $
:Status: Current
The ``transform_concat--tjl`` PEG left one type
of concatenation out, which will make things slightly
more efficient. Concatenating the inverse of one coordinate
system to another can be done in a single operation instead of
two.
This is a useful operation in, e.g., the View2D stuff in FenPDF.
Issues
======
Changes
=======
The OpenGL libvob already implements invert as ::
public int invert(int f) {
return concatInverse(0, f);
}
This peg proposes to add concatInverse into the official
VobScene definition.
Add into VobScene::
public int concatInverseCS(int into, Object key, int other) ;
and VobCoorder::
/** Create a new transformation that is the concatenation
* of an existing transformation and the inverse of another
* transformation.
* If we look at the transformations as x' = f(x) and x' = g(x) then
* the result of this operation is a transformation h,
* for which h(x) = f(g^-1(x)) always.
*/
public int concatInverse(int f, int g) ;
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