Re: [AD] Pixel graphics routines and transformations

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-----Original Message-----
From: Thomas Fjellstrom <tfjellstrom@xxxxxxxxxx>
To: Coordination of admins/developers of the game programming libraryAllegro <alleg-developers@xxxxxxxxxx>
Sent: Tue, Mar 23, 2010 4:33 am
Subject: Re: [AD] Pixel graphics routines and transformations


On March 22, 2010, Pavel Sountsov wrote:
One of the last bits that still does not play completely well with
transformations are the pixel drawing routines (al_draw_pixel,
al_put_pixel and al_get_pixel). It is no problem, of course, to
implement the appropriate functionality... but the question is what to
do with the primitives addon, which relies on them reasonably heavily.
The software component of the addon does all the transformations
itself,
and requires the pixel putting routines to be untransformed. It uses
al_draw_pixel for blended primitives, and al_put_pixel for non-blended
ones. Several solutions come to mind:

1. The simplest solution is to make all those functions respect the
transformations, and modify the addon to reset the transformations to
identity before it draws anything

2. Make a subset of those pixel drawing routines ignore
transformations
(e.g. al_put_pixel and al_get_pixel). However, this requires a
solution
for blended primitives (which need an untransformed equivalent to
al_draw_pixel).

3. Avoid the whole issue by making all pixel drawing routines ignore
transformations.

In addition to the above considerations, there may be teleological
concerns. It might not even make sense for al_put_pixel/al_get_pixel
to
be affected by transformations since those are not 'true' graphics
operations, instead being something that is used to modify textures or
whatnot.

Any thoughts?

I thought the last couple times this came up the decision was to transform
draw_pixel and leave put_pixel untransformed.

-SiegeLord


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--
Thomas Fjellstrom
tfjellstrom@xxxxxxxxxx

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