MSAA and Scene anti aliasing

[Mario Torre]

At first I was about to reply a +1 to Kevin, but then I realised:

1. This is indeed an area where people want to know the implementation
details.

2. An enum can be extended with different implementations, for example add
a non MSAA to the mix.

The drawback is that the enum may grow just for the need to add a new
property to the AA algorithm. I'm not sure how likely this is, but I didn't
see that many actual implementations to consider that an issue.

If this is the case, one may have a descriptor object passed rather than an
enum, so that external implementations may easily extend/replace the
default code.

The descriptor could be an opaque type so that the code that needs to
handle knows about it, but for users it still behaves like if it was an
enum. In fact, the defaults may even be collected in an enum again.

Cheers,
Mario
Il giorno 15/lug/2013 01:24, "Richard Bair" <richard.bair at oracle.com> ha
scritto:

> I know iOS gives at least two or three options. A single enum seems
> cleaner than two properties (and yet another constructor! Speaking of which
> it would be better if this were a mutable property).
>
> Is it that you don't like that some options can't be honored?
>
> On Jul 13, 2013, at 12:00 PM, Kevin Rushforth <kevin.rushforth at oracle.com>
> wrote:
>
> > I don't really like the single enum approach. I would prefer to keep the
> existing MSAA boolean, and then, if needed, add a separate attribute for
> requesting the number of samples; if desired there could be a read-only
> attribute that returns the actual number of samples used. Most chipsets
> give limited (or no) control over the number of samples anyway so an enum
> doesn't seem like a good fit.
> >
> > -- Kevin
> >
> >
> > Gerrit Grunwald wrote:
> >> +1 for the enum approach...will make it easier to enhance for future
> options...
> >>
> >> Gerrit
> >> Am 12.07.2013 um 19:55 schrieb Richard Bair <richard.bair at oracle.com>:
> >>
> >>
> >>> Thor recently pushed an implementation for MSAA for those cases when
> the feature is supported by the card and where a Scene (or SubScene) is
> created with the antiAliasing flag set to true. MSAA is "Multi-sampled Anti
> Aliasing", which means that the graphics card, when configured in this
> mode, will sample each fragment multiple times. The upshot is that 3D
> doesn't look as jaggy.
> >>>
> >>> However this has an impact on performance (usually an extra buffer
> copy or at the very least you will be sampling each pixel multiple times so
> if you are doing something graphically intense then that might push you
> over the edge where you start to see performance degradation). Now
> multi-sampling can be 2x, 4x, etc. The higher the multi-sampling value, the
> better the quality, and the lower the performance.
> >>>
> >>> I'm also bothered but the name "antiAliasing" because there are many
> forms of anti-aliasing in the world and it isn't clear which this is. I
> think perhaps we should instead have an enum. The idea is that we can add
> to the enum over time with greater options for how to perform the scene
> antialiasing.
> >>>
> >>> public enum SceneAntiAliasing {
> >>>   DISABLED,
> >>>   DEFAULT,
> >>>   MSAA_2X,
> >>>   MSAA_4X
> >>> }
> >>>
> >>> And then grow it over time to include potentially other techniques. My
> thought here is that the implementation is going to matter to folks.
> They're going to want to be able to make the performance / quality
> tradeoff, and perhaps even the implementation tradeoff (since different
> implementations may provide somewhat different results). DISABLED turns it
> off, obviously. DEFAULT allows us to pick what we think is the best (might
> be different on different platforms. Desktop might go with MSAA_16x or
> equivalent while iOS might be MSAA_2X). Then some standard options.
> >>>
> >>> Thoughts?
> >>> Richard
> >>>
>