Hi,
On 31/05/11 23:52, Kris Dale wrote:
Greetings all,
I've been learning PBOs here lately, and I can't seem to find any
tutorials about how to use OSG::PixelBufferObjects. If anyone can
point me in the direction of one, that would be awesome, as I
wouldn't have to mix OGL and OSG code quite as much as I'm doing
now.
Right now what I'm doing is trying to copy back the frame buffer to a
PBO each frame, but I can't get glGenBuffers to return a valid buffer
ID. I've tried passing in a single int or an array, but all I get
back are 0's. (In a strict GLUT/GL project, I get 1,2,3..)
I've made sure (as much as I can) that I have a context.. I've
created a graphicscontext, a window exists, I've called
viewer.realize(), even tried one viewer.frame() before glGenBuffers.
All I can get back are 0's. So naturally when I try to bindbuffer /
readpixels / mapbuffer, I just get back a null pointer because my
bufferID is zero.
Can anyone suggest a reason this might be happening? (Even if you
can point me to a good OSG tutorial on using OSG::PixelBufferObjects,
I'd still be curious to know.)
Thanks in advance for any guidance anyone can offer..
you'll probably have to stick your code into a camera callback to make
sure you have a valid context.
See the osgscreencapture example for some use of PBO. I also paste some
small example below that shows some methods for reading back texture data.
HTH
jp
--8<--
struct GPURegionOfInterestCallback : public osg::Camera::DrawCallback
{
GPURegionOfInterestCallback(ImageFormat& imf,
osg::Image *osg_im,
osg::TextureRectangle *tex) :
ImageFormat_(imf),
osg_im_(osg_im),
trect_(tex)
{
pdbo_ = new osg::PixelDataBufferObject();
pdbo_->setDataSize(ImageFormat_.getBytesPerImage());
}
virtual void operator() (osg::RenderInfo& renderInfo) const
{
// first get the texture into the pbo
pdbo_->bindBufferInWriteMode(*renderInfo.getState());
renderInfo.getState()->applyTextureAttribute(0, //unit
trect_);
glGetTexImage(trect_->getTextureTarget(),
0, //level
GL_LUMINANCE,
GL_UNSIGNED_BYTE,
NULL);
// now copy to cpu
osg::GLBufferObject::Extensions* ext =
osg::GLBufferObject::getExtensions(renderInfo.getState()->getContextID(), true);
GLubyte* src =
(GLubyte*)ext->glMapBuffer(GL_PIXEL_PACK_BUFFER_ARB,
GL_READ_ONLY_ARB);
if(src)
{
memcpy(osg_im_->data(), src,
osg_im_->getTotalSizeInBytes());
ext->glUnmapBuffer(GL_PIXEL_PACK_BUFFER_ARB);
}
pdbo_->unbindBuffer(renderInfo.getState()->getContextID());
/*
// direct to image from texture
renderInfo.getState()->applyTextureAttribute(0, //unit
trect_);
glGetTexImage(trect_->getTextureTarget(),
0, //level
GL_LUMINANCE,
GL_UNSIGNED_BYTE,
osg_im_->data());
*/
}
ImageFormat ImageFormat_;
osg::Image* osg_im_;
osg::TextureRectangle* trect_;
osg::ref_ptr<osg::PixelDataBufferObject> pdbo_;
};
Kris
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