Hi Sebastian
2012/10/30 Sebastian Messerschmidt <sebastian.messerschm...@gmx.de>
> Hello,
>
> I'm trying to implement an advanced HDR lighting algorithm where I need
> the average luminance of the last frame(s).
> Currently I've encountered two major problems:
>
> 1. Is there a possibility to get only the last mipmap-level from
> texture/image bound to a FBO?
> I can get the whole image via readImageFromCurrentTexture in a
> postDrawCallback, but this unfortunately copies the complete texture.
> Looking at the code, I see that all mipmap levels are copied, and my
> question is if it would be feasible to either create a special function to
> copy only a specific mipmap-level or add an additional parameter to the
> function to specifiy the mipmap level?
>
I don't see any code in OSG to just read specific mipmap level, but with
"readImageFromCurrentTexture" code as model, this will not be difficult to
do appropriate function.
> 2. I have trouble getting correct values from floating point buffers. It
> works if get the values as GL_UNSIGNED_BYTE (the values are indeed scaled
> to 0 -255) but this, of course, won't be precise enough as the buffer holds
> the logarithmic luminance.
check this :
- be sure to bind correct texture in Texture 0 :
state->applyTextureAttribute(0, myTextureToRead);
- be sure to active correct Texture Unit :
state->setActiveTextureUnit(0);
- be sure current texture have FLOAT internal Type :
osg::Image::computeFormatDataType(myTextureToRead->getInternalFormat()) ==
GL_FLOAT
And when you did
double data = *image->getMipmapData(0);
you read the buttom left pixel of the complet image, average luminance is
in the last mipmap level
double averageLuminance = *reinterprete_cast<double*>(
image->getMipmapData(image->getNumMipmapLevels() - 1) );
HTH
David
Below you find a snippet of my PostDrawCallback, maybe I'm doint something
> fundamentally wrong.
> I'm running on OSG 3.0.1.
>
> virtual void operator () (osg::RenderInfo& render_info) const
> {
> //state->apply(render_info.**getCurrentCamera()->**getStateSet());
> //state->**applyTextureAttribute(0,**mTexture);
> //mTexture->apply(*state);
> osg::ref_ptr<osg::Image> image=new osg::Image();
> mTexture->getImage()->**readImageFromCurrentTexture(**
> render_info.getContextID(),**true, GL_UNSIGNED_BYTE); //works , doesn't
> work with GL_FLOAT
> double data = *image->getMipmapData(0);
> std::cout << "luminance " << data << std::endl;
> //osgDB::writeImageFile(***image,"snap.bmp");
> }
>
>
> cheers
> Sebastian
>
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