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List:       kde-devel
Subject:    Re: plans for a free, OpenGL-based equivalent to Direct2D ?
From:       Reece Dunn <msclrhd () googlemail ! com>
Date:       2010-12-14 9:16:03
Message-ID: AANLkTimX33g6RyQLcvaoVTW9oY=EB8LUUziiA=SsZXPh () mail ! gmail ! com
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On 14 December 2010 08:12, Benoit Jacob <jacob.benoit.1@gmail.com> wrote:
> 2010/12/14 Thiago Macieira <thiago@kde.org>:
>> On Tuesday, 14 de December de 2010 09:01:05 Benoit Jacob wrote:
>>> We target every OpenGL ES 2 device. I am not aware of an OpenVG
>>> implementation that will run (and be well hardware-accelerated)
>>> everywhere there is a OpenGL ES 2 implemetation?
>>
>> You asked for a hardware-accelerated API. But given your current reply, I take
>> that you're looking for a 2D abstraction layer on top of OpenGL.
>
> Right, I'm looking at a 2D library that's accelerated by OpenGL.
> However, "abstraction layer" is not how I would call it, because
> really it's not just about abstraction, it's going to have to
> _implement_ lots of stuff, part of which will have to run on the CPU,
> not on the GPU.  2D is hard in that CPU and GPU tasks tend to be
> intermingled in a way that makes it quite hard to offload to the GPU.

IIUC, you want a library that meets the following requirements:

=== Core Library

1.  a library that wraps OpenGL calls
2.  support different OpenGL profiles -- e.g. 2.1 (desktop) and ES 2.0 (mobile)
3.  offloads as much work onto the GPU as possible
4.  uses OpenGL-based buffers as much as possible with few round-trips
to memory-based buffers -- get the most performance, reduce roundtrip,
etc.

=== Capabilities

1.  a vector-based 2D API -- e.g. for svg support -- that constructs
an OpenGL scene graph
2.  create texture from images -- png, jpg, gif, bmp, custom, etc. --
to support rendering, scaling, etc. of images
3.  transformations (scaling, rotating, translating) done as
OpenGL-based matrix transforms
4.  font selection/enumeration -- i.e. fontconfig support
5.  text positioning/layout -- i.e. pango support
6.  transparency -- offload alpha-blending to OpenGL/the GPU
7.  other effects -- offload as many effects as possible to OpenGL
8.  animations/timers/events -- need support for these, offloading to
OpenGL to do the transitions where possible

- Reece
 
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