------------------------------------------------------------------------
*From:* [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] *On Behalf Of *Viggo
L?vli
*Sent:* Monday, June 02, 2008 11:29 AM
*To:* OpenSceneGraph Users
*Subject:* Re: [osg-users] I get errors when trying to render to a
luminance buffer...
Hi again :-)
I abandoned the idea of using a floating point buffer.
I went into the thinking box and came to the same conclusion as you
wrote about in the end of your comment.
I needed a quite high resolution so I decided to use all 4 channels
(RGBA). The numbers I want to accumulate is seldom large, so I needed
most resolution in the lower scale.
I thus decided to use RGBA where R is most significant and A is least
significant.
Bit usage is:
R = 6 bits
G = 5 bits
B = 4 bits
A = 3 bits
All non used bits will overlap with next channel.
I am using this to generate a pixel weight when rendering many
volumetric clouds on top of each other on screen. Naturally most
overlapping clouds will be further away from camera, so I needed as high
a number of overlap bits on the lest significant buffers that I could
get. My usage accepts in worst case 32 overlapping pixels with maximum
weight (in the distance). I think that is something I can live with :-)
Anyhow, I got a range (18 bit) that was good enough for my usage and it
gives a decent cloud sorting for clouds seen up to 40 kilometers away.
I must stress one point:
- If you ever try using the alpha channel for this then remember to turn
off alpha-clipping (set alpha-func to always).
Viggo
Date: Mon, 2 Jun 2008 10:05:24 +0200
From: [EMAIL PROTECTED]
To: [email protected]
Subject: Re: [osg-users] I get errors when trying to render to a
luminance buffer...
Hi,
Viggo Løvli wrote:
> Ok, that make sense.
> It happens every time I render with a floating point texture.
>
> The fall in framerate does not happen when I run the OSG multi render
> target example using HDR. My code does however use additive blending
> toward the floating point texture so I bet that is what cause it to
fall
> into a software rendering mode.
We have also experienced this slowdown when blending was enabled with
float textures. Testing on newer cards is pending as we cannot figure
out from docs on the internet if this is actually supported in current
hardware at all. Seems like DX10.1 mandates float blending, but we will
test to make sure. Please let me know if you know if it is supported in
hardware.
>
> Do you know about any texture surface bit format that is more than 8
> bits (unsigned integer) ?
I don't know of any. I've only seen a paper once where people were using
three channels to simulate one large channel. The RGB channels were
partially overlapped to create a higher dynamic range channel.
jp
>
> Viggo
>
>
> > Date: Fri, 30 May 2008 16:29:05 +0100
> > From: [EMAIL PROTECTED]
> > To: [email protected]
> > Subject: Re: [osg-users] I get errors when trying to render to a
> luminance buffer...
> >
> > Hi Viggo,
> >
> > When performance drops like this it's because you've dropped onto a
> > software fallback path in the OpenGL driver. Exactly what formats are
> > software vs hardware depends upon the hardware and OpenGL drivers.
> > You'll need to check with your hardware vendors specs to see what will
> > be hardware accelerated.
> >
> > Robert.
> >
> > On Fri, May 30, 2008 at 2:16 PM, Viggo Løvli <[EMAIL PROTECTED]>
wrote:
> > > Hi Robert,
> > >
> > > I modified my code as you suggested.
> > > The warning is gone :-)
> > >
> > > The framerate is now 10 seconds per frame instead of 30 frames per
> second.
> > > It does something.
> > > The texture I render to remains black (cleared to black).
> > >
> > > If I change the setInternalFormat to GL_RGBA then the framerate is
> up again,
> > > and the texture gets colors. This works, but then I only have 8 bit
> in the
> > > red channel. What I need is as many bits as possible in the red
> channel,
> > > preferably 32. And I do not need GBA channels.
> > > Do you have a suggestion for me on this one?
> > >
> > > Viggo
> > >
> > >> Date: Fri, 30 May 2008 13:25:24 +0100
> > >> From: [EMAIL PROTECTED]
> > >> To: [email protected]
> > >> Subject: Re: [osg-users] I get errors when trying to render to a
> luminance
> > >> buffer...
> > >>
> > >> Hi Viggo,
> > >>
> > >> The warning is exactly right, pbuffers don't suport multiple render
> > >> targets, only FrameBufferObjects do.
> > >>
> > >> Perhaps what you intend it not to use multiple render targets, in
> > >> which case you should set the Camera attachment to COLOR_BUFFER
rather
> > >> than COLOR_BUFFER0, that later tells the OSG that you want MRT and
> > >> will be using glFragColor[] in your shaders.
> > >>
> > >> Also the Camera::setDrawBuffer(GL_COLOR_ATTACHMENT0_EXT) is
> > >> inappropriate for pbuffers.
> > >>
> > >> Robert.
> > >>
> > >> On Fri, May 30, 2008 at 1:18 PM, Viggo Løvli <[EMAIL PROTECTED]>
> wrote:
> > >> > Hi,
> > >> >
> > >> > I want to render to a floating point buffer, and I set things up
> like
> > >> > this:
> > >> >
> > >> > tex->setInternalFormat( GL_LUMINANCE16F_ARB );
> > >> > tex->setSourceFormat( GL_RED );
> > >> > tex->setSourceType( GL_FLOAT );
> > >> >
> > >> > camera->setRenderTargetImplementation(
> osg::Camera::FRAME_BUFFER_OBJECT
> > >> > );
> > >> > camera->attach( osg::Camera::BufferComponent(
> osg::Camera::COLOR_BUFFER0
> > >> > ),
> > >> > tex );
> > >> > camera->setDrawBuffer( GL_COLOR_ATTACHMENT0_EXT );
> > >> >
> > >> > My fragment-shader that write to the surface output the value
> this way:
> > >> > gl_FragData[0].r = 1.0;
> > >> >
> > >> > Another fragment-shader reads the surface this way:
> > >> > value = texture2DRect( id, gl_FragCoord.xy ).r;
> > >> >
> > >> > I get the following output when I try to run my app:
> > >> > "Warning: RenderStage::runCameraSetUp(state&) Pbuffer does not
> support
> > >> > multiple color outputs."
> > >> >
> > >> > My app runs, but nothing is written to the texture.
> > >> >
> > >> > Is it possible to set up a surface that holds one channel
> (GL_RED) which
> > >> > is
> > >> > an unsigned int of 32 bit resolution? I'd rather use that than a
> float
> > >> > :-)
> > >> >
> > >> > Viggo
> > >> >
> > >> > ________________________________
> > >> > Få Hotmail du også. Windows Live Hotmail nå med 5000 MB gratis
> > >> > lagringsplass.
> > >> > _______________________________________________
> > >> > osg-users mailing list
> > >> > [email protected]
> > >> >
> > >> >
>
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> > >> >
> > >> >
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> > >>
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> > >
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