Re: [AD] 5.1?

[Pavel Sountsov <slabode@xxxxxxxxxx>]

> On Tue, Apr 27, 2010 at 12:46 AM, Trent Gamblin <trent@xxxxxxxxxx> 
wrote:
> On Mon, April 26, 2010 4:11 pm, Elias Pschernig said:
> > What are the drawbacks of removing parallelogram_map completely?
>
> That function is the greatest evil in all of Allegro... but it works 
and is
> decently fast... But IMO if it can be rewritten more clearly that 
would be
> great.
>
> That wouldn't help with the code duplication and the transformation 
issue at all so not too much point. What I meant was, the function 
seems to be (I'm not really sure) redundant. The same thing can be done 
with the primitives addon.

The primitives addon only has a triangle rasterizer, while the MAP 
function is a parallelogram rasterizer (which will have to be rewritten 
into a generalized quadrangle rasterizer). Now, you can implement the 
latter using two triangle rasterizers, but in principle it is a 
separate function.

Thus, if rewritten, code duplication will be relatively minimal. 
Whether rewriting it is better than using the primitives addon's 
triangle rasterizer twice is another question. It should be more 
efficient, in principle to use a dedicated quadrangle rasterizer (it 
may be fun to benchmark the current implementations against each 
other). It is certainly faster (in terms of development time) to just 
use the primitives addon.

> > But anyhow, I can easily keep the current 2D transforms as they are
> > and create a 3D transform addon or something. I think it would work,
> > but the core would depend on it anyway I guess, since as I said, the
> > 2D transformation API produced incorrect results (for whatever 
reason)
> > when I first tried using it for the iPhone landscape transformation. 
I
> > know that involves an orthographic projection which is a 3D thing,
> > but even when I temporarily removed it for testing, the comparison to
> > the OpenGL matrix was off, and all of the other transforms are 2D.
>
> I'd say a general 4x4 matrix transformation is sufficiently standard 
to use for our transformations API. Even Flash which is 100% 2D uses a 
full 4x4 matrix for transformations. So if at all possible I'd say we 
shouldn't limit the transformation API to 2D only.

The current transformations are 4x4 matrices, so it's only a matter of 
choice of what the functions do. The difference between sticking 3D 
functions into the addon vs the core is whether the core (specifically 
the aforementioned PARALLELOGRAM_MAP) supports the 3D transformations. 
If they are in the addon, the support is obviously optional.

-SiegeLord