Hi Robert,
At the first sight I would prefer adding a new property to
osg::Camera::Attachment, which should be clear to MRT related programs. But as
Sebastian tells, there is also the draw_buffers_blend extension, which requires
buffer ID for separated blending functions. This may lead us to rewrite the
osg::BlendFunc and osg::BlendEquation implementations later.
I would first try to migrate current code to osg::Camera this weekend, if my
four-months old daughter agrees. :-)
Wang Rui
------------------ Original ------------------
From: "Robert Osfield";<[email protected]>;
Date: Fri, Nov 21, 2014 01:52 AM
To: "OpenSceneGraph Submissions"<[email protected]>;
Subject: Re: [osg-submissions] Separated blending for multiple renderingtargets
Hi Rui,
Sorry for the slow review. Just done a review and feel that how best to
implement this feature is something we need to discuss further.
The issue with the proposed implementation is that state will leak from the
osg::BlendFunc that you set the DrawBufferState on and will affect any MRT
usage out with the subgraph that you apply it to. Normally with OSG state the
default constructed version of a StateAttribute is applied once all the version
of that state have been popped off the osg::State stack for that attribute.
This won't be possible with these modifications of osg::BlendFunc, and the
design won't really expand easily to handle this case.
My own inclination is that this feature is more closely aligned with the set up
of a MRT osg::Camera and it's subgraph, the MRT Camera knows exactly how many
buffers it managing, and at setup the user propbably knows whether blending is
required, so perhaps the osg::Camera::Attachment should be extended to handle
this case.
Another alternative would be to have a separate StateAttribute for this new
control rather than place it with osg::BlendFunc. This would still have the
issue of how do we manage return the state to appropriate defaults.
Thoughts?
Robert.
On 9 August 2014 17:51, Wang Rui <[email protected]> wrote:
Hi Robert,
I've just implemented part of the GL_EXT_draw_buffers2 extension in
osg::BlendFunc, which is necessary especially for deferred shading use. It
enables developers to decide which of the multiple rendering targets (MRT) can
be affected by blending function. Those targets disabling blending are always
treated as to save extra geometry attributes in all 4 channels rather than
opacity.
This submissions is originated from the following topic in the mail list:
http://forum.openscenegraph.org/viewtopic.php?t=13057
And about the extension:
http://www.opengl.org/registry/specs/EXT/draw_buffers2.txt
A new osgblenddrawbuffers example is also submitted to show the importance and
usage of the new functionalities.
Cheers,
Wang Rui
_______________________________________________
osg-submissions mailing list
[email protected]
http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org
_______________________________________________
osg-submissions mailing list
[email protected]
http://lists.openscenegraph.org/listinfo.cgi/osg-submissions-openscenegraph.org
