我目前正在使用离屏渲染器，以便我可以为真实场景进行互信息注册。我使用OpenSceneGraph来处理大数据和自动加载。我在顺序的单线程程序中获取帧缓冲区时遇到了麻烦。
好吧，我有这个课程（标题）：
#include <osg/ref_ptr>
#include <osg/Array>
#include <osg/ImageUtils>
#include <osgGA/StateSetManipulator>
#include <osgViewer/Viewer>
#include <osg/GraphicsContext>
#include <osg/Texture2D>
#include <osg/FrameBufferObject>
#include <osgDB/WriteFile>
#include <osg/Referenced>
#include <osg/Vec3>
#include <osg/Image>
#include <osg/State>
#include <string>
#include <chrono>
#include <thread>
#include <assert.h>
#include "ImagingPrimitives.h"
class BoundRenderScene {
public:
BoundRenderScene();
virtual ~BoundRenderScene();
void NextFrame(void);
inline OpenThreads::Mutex* GetMutexObject(void) { return &_mutex; }
inline osg::Image* GetFrame(void)
{
OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
return _frame.get();
}
inline void GetFrame(osg::Image* img)
{
OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
if(_frame.valid() && (img!=NULL) && img->valid())
{
glReadBuffer(GL_BACK);
img->readPixels(0,0,_camera_configuration->GetSX(),_camera_configuration->GetSY(), GL_RGB,GL_UNSIGNED_BYTE);
uint w = img->s(), h = img->t(), d = img->r(), c = uint(img->getPixelSizeInBits()/8);
/*
* bare testing write op
* osgDB::writeImageFile(const_cast<const osg::Image&>(*img), "/tmp/testimg.png");
*/
}
}
inline void SetCameraConfiguration(CameraConfiguration* configuration) { _camera_configuration = configuration; }
inline void SetCameraMatrix(osg::Matrixd camera_matrix) { _camera_matrix = camera_matrix; }
inline void SetScene(osg::Node* scene) { _scene = scene; }
inline void Initialize(void) {
if(!_initialized)
_init();
else
_re_init();
}
protected:
osgViewer::Viewer _viewer;
osg::Matrixd _camera_matrix;
osg::ref_ptr<osg::Texture2D> _tex;
osg::ref_ptr<osg::FrameBufferObject> _fbo;
mutable osg::ref_ptr<osg::Image> _frame;
osg::ref_ptr<osg::Node> _scene;
osg::ref_ptr<osg::GraphicsContext::Traits> _traits;
osg::ref_ptr<osg::GraphicsContext> _gc;
CameraConfiguration* _camera_configuration;
SnapshotCallback* cb;
std::string _filepath;
private:
void _init(void);
void _re_init(void);
bool _initialized;
mutable OpenThreads::Mutex _mutex;
osg::Matrixd pre_transform;
osg::Matrixd transformation;
};
此外，由于屏幕外渲染和屏幕捕获中的许多示例都使用Post / FinalDrawCallaback，我从“osgdistortion”示例中复制了回调结构，但添加了用于同步的互斥锁：
struct SnapshotCallback : public osg::Camera::DrawCallback
{
public:
inline SnapshotCallback(OpenThreads::Mutex* mtx_obj, std::string filepath, int width, int height) : _filepath(filepath), _output_to_file(false), _mutex(mtx_obj)
{
_image = new osg::Image();
_image->allocateImage(width, height, 1, GL_RGB, GL_UNSIGNED_BYTE);
if(filepath!="")
_output_to_file = true;
}
inline virtual void operator() (osg::RenderInfo& renderInfo) const
{
OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*_mutex);
osg::Camera* camera = renderInfo.getCurrentCamera();
osg::Viewport* viewport = camera ? camera->getViewport() : 0;
if(viewport && _image.valid())
{
glReadBuffer(GL_BACK);
_image->readPixels(int(viewport->x()),int(viewport->y()),int(viewport->width()),int(viewport->height()), GL_RGB, GL_UNSIGNED_BYTE);
if(_output_to_file)
{
osgDB::writeImageFile(*_image, _filepath);
}
}
}
inline virtual void operator() (const osg::Camera& camera) const
{
OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*_mutex);
osg::Viewport* viewport = camera.getViewport();
if(viewport && _image.valid())
{
glReadBuffer(GL_BACK);
_image->readPixels(int(viewport->x()),int(viewport->y()),int(viewport->width()),int(viewport->height()), GL_RGB, GL_UNSIGNED_BYTE);
if(_output_to_file)
{
osgDB::writeImageFile(*_image, _filepath);
}
}
}
std::string _filepath;
bool _output_to_file;
mutable OpenThreads::Mutex* _mutex;
mutable osg::ref_ptr<osg::Image> _image;
};
我按如下方式初始化并渲染场景：
#include "BoundRenderScene.h"
void BoundRenderScene::_init(void)
{
if(_camera!=NULL)
_viewer.setDone(true);
_traits->x = 0;
_traits->y = 0;
_traits->width = _camera_configuration->GetSX();
_traits->height = _camera_configuration->GetSY();
_traits->red = 8;
_traits->green = 8;
_traits->blue = 8;
_traits->alpha = 0;
_traits->depth = 24;
_traits->windowDecoration = false;
_traits->pbuffer = true;
_traits->doubleBuffer = true;
_traits->sharedContext = 0x0;
if(_gc.get()!=NULL)
{
bool release_success = _gc->releaseContext();
if(!release_success)
std::cerr << "Error releasing Graphics Context.";
}
_gc = osg::GraphicsContext::createGraphicsContext(_traits.get());
_viewer.getCamera()->setGraphicsContext(_gc.get());
_viewer.setThreadingModel(osgViewer::Viewer::SingleThreaded);
_viewer.setUpThreading();
_viewer.realize();
_frame->allocateImage(_camera_configuration->GetSX(), _camera_configuration->GetSY(), 1, GL_RGB, GL_UNSIGNED_BYTE);
_viewer.getCamera()->getOrCreateStateSet();
_viewer.getCamera()->setRenderTargetImplementation(osg::Camera::PIXEL_BUFFER);
cb = new SnapshotCallback(&_mutex,_filepath, _camera_configuration->GetSX(), _camera_configuration->GetSY());
//_viewer.getCamera()->setPostDrawCallback( cb );
//Clear colour "black" for representing "no information" => background elimination in natural image, pls.
_viewer.getCamera()->setClearColor(osg::Vec4f(0.25f, 0.25f, 0.25f, 1.0f));
_viewer.getCamera()->setClearMask(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
_viewer.getCamera()->setDrawBuffer(GL_BACK);
_viewer.getCamera()->setReadBuffer(GL_BACK);
_viewer.getCamera()->setViewport(0,0,_camera_configuration->GetSX(),_camera_configuration->GetSY());
_viewer.getCamera()->setProjectionMatrix(osg::Matrixd::perspective(osg::RadiansToDegrees(_camera_configuration->GetFoV()), _camera_configuration->GetAspectRatio(), 0.1, 150.0));
//looking in geo-coord system
_viewer.getCamera()->setViewMatrix(osg::Matrixd::lookAt(osg::Vec3d(0.0, 0.0, -1.0), osg::Vec3d(0.0, 0.0, 1.0), osg::Vec3d(0.0, 1.0, 0.0)));
_viewer.getCamera()->attach(osg::Camera::COLOR_BUFFER, _frame.get());
_viewer.getCamera()->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);
_tex->setTextureSize(_camera_configuration->GetSX(), _camera_configuration->GetSY());
_tex->setInternalFormat(GL_RGB);
_tex->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);
_tex->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
_tex->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
_tex->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
_tex->setResizeNonPowerOfTwoHint(false);
_tex->setImage(0,_frame.get());
_fbo->setAttachment(osg::Camera::COLOR_BUFFER, osg::FrameBufferAttachment(_tex.get()));
_viewer.setDone(false);
_viewer.setSceneData(_scene.get());
_viewer.setCameraManipulator(0x0);
}
void BoundRenderScene::NextFrame(void)
{
OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
if(_frame.valid() && !_viewer.done())
{
osg::Matrixd inverse_cam = osg::Matrixd::inverse(_camera_matrix);
transformation = inverse_cam * pre_transform;
_viewer.getCamera()->setViewMatrix(transformation);
_viewer.updateTraversal();
_viewer.frame();
}
else
std::cout << "Viewer or Camera invalid." << std::endl;
}
主要工作流程如下（简化）：
BoundRenderScene renderer;
std::vector<osg::Matrixd> poses;
/*
* setting initial parameters
* fill poses with camera positions to render, for regsitration
*/
renderer._init();
for(uint i = 0; i < poses.size(); i++)
{
renderer.SetCameraMatrix(poses.at(i));
renderer.NextImage();
sleep(0.04); // to get the 25fps frame limit
osg::Image* reg_image = renderer.GetImage();
/*
* Do further processing
*/
}
现在出现了关键：OpenSceneGraph示例“osgprenderer”（包含在OSG中）使用osg :: Camera :: DrawCallback作为我的SnapshotCallback进行屏幕外渲染。不幸的是，在我的情况下，operator（） - 函数永远不会在我的场景图中被调用，所以这种屏幕捕获方式对我来说不起作用。它也相当不方便，因为互信息程序的其余部分是一个相当顺序的管道。
其他包装器（https://github.com/xarray/osgRecipes/blob/master/integrations/osgberkelium/osgberkelium.cpp）使用类似于我的“void GetFrame（osg :: Image * img）”方法的方法，其中使用“readPixels”主动读取图像。这对我的工作流程非常方便，但该方法始终返回空白图像。它不会崩溃，但它也不会发挥作用。
可行的方法是“osg：and：Image * GetFrame（void）”，它返回绑定/附加的FBO图像。它类似于“osgdistortion”示例。它可以用于渲染一到两个图像，但经过一段时间后，渲染和处理失去同步，应用程序崩溃如下：
[---FIRST FRAME---]
GraphicsCostEstimator::calibrate(..)
cull_draw() 0x1998ca0
ShaderComposer::~ShaderComposer() 0x35a4d40
Renderer::compile()
OpenGL extension 'GL_ARB_vertex_buffer_object' is supported.
OpenGL extension 'GL_EXT_secondary_color' is supported.
OpenGL extension 'GL_EXT_fog_coord' is supported.
OpenGL extension '' is not supported.
OpenGL extension 'GL_EXT_packed_depth_stencil' is supported.
Setting up osg::Camera::FRAME_BUFFER_OBJECT
end cull_draw() 0x1998ca0
[processing]
[ SECOND FRAME ]
cull_draw() 0x1998ca0
OpenGL extension 'GL_ARB_fragment_program' is supported.
OpenGL extension 'GL_ARB_vertex_program' is supported.
OpenGL extension 'GL_ARB_shader_objects' is supported.
OpenGL extension 'GL_ARB_vertex_shader' is supported.
OpenGL extension 'GL_ARB_fragment_shader' is supported.
OpenGL extension 'GL_ARB_shading_language_100' is supported.
OpenGL extension 'GL_EXT_geometry_shader4' is supported.
OpenGL extension 'GL_EXT_gpu_shader4' is supported.
OpenGL extension 'GL_ARB_tessellation_shader' is supported.
OpenGL extension 'GL_ARB_uniform_buffer_object' is supported.
OpenGL extension 'GL_ARB_get_program_binary' is supported.
OpenGL extension 'GL_ARB_gpu_shader_fp64' is supported.
OpenGL extension 'GL_ARB_shader_atomic_counters' is supported.
glVersion=4.5, isGlslSupported=YES, glslLanguageVersion=4.5
Warning: detected OpenGL error 'invalid operation' at end of SceneView::draw()
end cull_draw() 0x1998ca0
[-FROM 3rd FRAME ONWARDS-]
[workload, matrix setup]
[_viewer.frame()]
cull_draw() 0x1998ca0
Warning: detected OpenGL error 'invalid operation' at start of State::apply()
end cull_draw() 0x1998ca0
[next frame]
[BREAKING]
cull_draw() 0x1998ca0
Warning: detected OpenGL error 'invalid operation' at start of State::apply()
end cull_draw() 0x1998ca0
[more work]
Segmentation fault (core dumped)
所以，问题是：
我查看了osg中与Viewer相关的类的源文件，但是我无法确定错误的位置
警告：在State :: apply（）
开始时检测到OpenGL错误'无效操作'来自。知道从哪里开始寻找它吗？
对于顺序渲染和截屏，哪种方法最适合在OSG中使用？
答案 0 :(得分：0)
随着更深入的研究结果发布，在类析构函数中释放图形上下文释放了OpenGL管道，但是：它还解除了加载的场景/模型的状态集绑定纹理，尽管模型本身没有被挂起（如在问题：它在以下过程中重复使用）。因此，在进一步的渲染过程中，渲染管道想要访问已通过释放GL上下文释放的OSG资产。
代码中的改为：
BoundRenderScene::~BoundRenderScene() {
// TODO Auto-generated destructor stub
_viewer.setDone(true);
_viewer.setReleaseContextAtEndOfFrameHint(true);
_gc->releaseContext();
#ifdef DEBUG
std::cout << "BoundRenderScene deleted." << std::endl;
#endif
}
为：
BoundRenderScene::~BoundRenderScene() {
// TODO Auto-generated destructor stub
_viewer.setDone(true);
_viewer.setReleaseContextAtEndOfFrameHint(true);
#ifdef DEBUG
std::cout << "BoundRenderScene deleted." << std::endl;
#endif
}
这解决了OpenSceneGraph内部错误消息。现在，为了解决帧捕获问题本身，我实现了osgprenderer的回调：
struct SnapshotCallback : public osg::Camera::DrawCallback
{
public:
inline SnapshotCallback(std::string filepath) : _filepath(filepath), _output_to_file(false), _image(NULL)
{
if(filepath!="")
_output_to_file = true;
_image = new osg::Image();
}
inline virtual void operator() (osg::RenderInfo& renderInfo) const
{
osg::Camera* camera = renderInfo.getCurrentCamera();
osg::Viewport* viewport = camera ? camera->getViewport() : 0;
if(viewport)
{
glReadBuffer(camera->getDrawBuffer());
_image->allocateImage(int(viewport->width()), int(viewport->height()), 1, GL_RGB, GL_UNSIGNED_BYTE);
_image->readPixels(int(viewport->x()),int(viewport->y()),int(viewport->width()),int(viewport->height()), GL_RGB, GL_UNSIGNED_BYTE);
if(_output_to_file)
{
osgDB::writeImageFile(*reinterpret_cast<osg::Image*>(_image->clone(osg::CopyOp::DEEP_COPY_ALL)), _filepath);
}
}
}
inline virtual void operator() (const osg::Camera& camera) const
{
osg::Viewport* viewport = camera.getViewport();
if(viewport)
{
glReadBuffer(camera.getDrawBuffer());
_image->allocateImage(int(viewport->width()), int(viewport->height()), 1, GL_RGB, GL_UNSIGNED_BYTE);
_image->readPixels(int(viewport->x()),int(viewport->y()),int(viewport->width()),int(viewport->height()), GL_RGB, GL_UNSIGNED_BYTE);
if(_output_to_file)
{
osgDB::writeImageFile(*reinterpret_cast<osg::Image*>(_image->clone(osg::CopyOp::DEEP_COPY_ALL)), _filepath);
}
}
}
inline osg::Image* GetImage(void)
{
return reinterpret_cast<osg::Image*>(_image->clone(osg::CopyOp::DEEP_COPY_ALL));
}
protected:
std::string _filepath;
bool _output_to_file;
mutable osg::ref_ptr<osg::Image> _image;
};
现在，使用克隆缓冲区而不是实际的图像缓冲区（从osgscreencapture示例中获取的想法），我确实得到了没有内存错误的真实图像。
对于双缓冲渲染，我虽然必须以某种方式渲染场景两次，以便正确的缓冲区包含对象的图像，但这对我的用例来说当前不是一个问题（I / O绑定渲染，而不是操作结合的）。
所以，主要功能如下：
BoundRenderScene renderer;
std::vector<osg::Matrixd> poses;
/*
* setting initial parameters
* fill poses with camera positions to render, for registration
*/
renderer._init();
for(uint i = 0; i < poses.size(); i++)
{
renderer.SetCameraMatrix(poses.at(i));
renderer.NextImage();
renderer.NextImage();
osg::Image* reg_image = renderer.GetImage();
/*
* Do further processing
*/
}