OpeneSceneGraph: using ray casting to perform drawing on 3D virtual plane

Canvas.cpp

#include "Canvas.h"

entity::Canvas::Canvas()
    : osg::Group()
    , m_transform(new osg::MatrixTransform)
    , m_switch(new osg::Switch)
    , m_frameGeode(new osg::Geode)
    , m_frameGeometry(new osg::Geometry)
    , m_dataGeode(new osg::Geode)
    , m_center(osg::Vec3(0,0,0))
    , m_normal(osg::Vec3(0,-1,0))
{
    osg::Vec3Array* vertices = new osg::Vec3Array;
    vertices->push_back( osg::Vec3(1.0f, 0.0f, 1.0f) );
    vertices->push_back( osg::Vec3(-1.0f, 0.0f, 1.0f) );
    vertices->push_back( osg::Vec3(-1.0f, 0.0f, -1.f) );
    vertices->push_back( osg::Vec3(1.0f, 0.0f, -1.0f) );

    osg::Vec4Array* colors = new osg::Vec4Array;
    colors->push_back( osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f) );
    colors->push_back( osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f) );
    colors->push_back( osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f) );
    colors->push_back( osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f) );

    this->addChild(m_transform.get());
    m_transform->addChild(m_switch.get());
    m_switch->addChild(m_frameGeode.get(), true);
    m_frameGeode->addDrawable(m_frameGeometry.get());
    m_switch->addChild(m_dataGeode.get());
    m_frameGeometry->setVertexArray(vertices);
    m_frameGeometry->setColorArray(colors);
    m_frameGeometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
    m_frameGeometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINE_LOOP,0,4));

    m_frameGeometry->dirtyDisplayList();
    m_frameGeometry->dirtyBound();
}

void entity::Canvas::addStroke(Stroke *stroke)
{
    m_dataGeode->addChild(stroke);
}

const entity::Stroke *entity::Canvas::getStroke(unsigned int i) const
{
    return dynamic_cast<Stroke*>(m_dataGeode->getChild(i));
}

void entity::Canvas::doStroke(float u, float v, int mouse)
{
    if (mouse == 0){
        m_stroke = new entity::Stroke;
        m_stroke->setBegin(u,v);
        m_dataGeode->addDrawable(m_stroke);
    }
    m_stroke->setEnd(u, v);
    if (mouse == 2)
        m_stroke = 0;
}

const osg::Vec3 &entity::Canvas::getCenter() const
{
    return m_center;
}

osg::Plane entity::Canvas::getPlane() const
{
    osg::Plane plane(m_normal, m_center);
    return plane;
}

osg::MatrixTransform *entity::Canvas::getTransform() const
{
    return m_transform.get();
}

entity::Canvas::~Canvas()
{

}

Canvas.h

#ifndef CANVAS_H
#define CANVAS_H

#include <osg/ref_ptr>
#include <osg/Group>
#include <osg/Switch>
#include <osg/Geode>
#include <osg/Geometry>
#include <osg/MatrixTransform>

#include "Stroke.h"

namespace entity
{
class Canvas : public osg::Group
{
public:
    Canvas();

    void addStroke(Stroke* stroke);
    const Stroke* getStroke(unsigned int i) const;
    void doStroke(float u, float v, int mouse);

    const osg::Vec3& getCenter() const;
    osg::Plane getPlane() const;
    osg::MatrixTransform* getTransform() const;

protected:
    ~Canvas();

private:
    osg::ref_ptr<osg::MatrixTransform> m_transform;
    osg::ref_ptr<osg::Switch> m_switch;
    osg::ref_ptr<osg::Geode> m_frameGeode;
    osg::ref_ptr<osg::Geometry> m_frameGeometry;
    osg::ref_ptr<osg::Geode> m_dataGeode;
    osg::ref_ptr<entity::Stroke> m_stroke;

    osg::Vec3 m_center;
    osg::Vec3 m_normal;
};
}

#endif // CANVAS_H

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)
project(osg-raycast)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

find_package(OpenSceneGraph REQUIRED COMPONENTS osgDB osgGA osgUtil osgViewer)

include_directories(${OPENSCENEGRAPH_INCLUDE_DIRS})

set(SOURCES
    osg-raycast.cpp
    Canvas.h
    Canvas.cpp
    Stroke.h
    Stroke.cpp
    EventHandler.h
    EventHandler.cpp
)

add_executable(${PROJECT_NAME} ${SOURCES})

target_link_libraries(${PROJECT_NAME}
    ${OPENSCENEGRAPH_LIBRARIES}
)

EventHandler.cpp

#include "EventHandler.h"

#include <iostream>
#include "vector"

#include <osgViewer/View>
#include <osg/Plane>

EventHandler::EventHandler(entity::Canvas *canvas)
    : osgGA::GUIEventHandler()
    , m_canvas(canvas)
{
}

bool EventHandler::handle(const osgGA::GUIEventAdapter &ea, osgGA::GUIActionAdapter &aa)
{
    if (!( (ea.getEventType() == osgGA::GUIEventAdapter::PUSH && ea.getButtonMask()== osgGA::GUIEventAdapter::RIGHT_MOUSE_BUTTON)
           || (ea.getEventType() == osgGA::GUIEventAdapter::DRAG && ea.getButtonMask()== osgGA::GUIEventAdapter::RIGHT_MOUSE_BUTTON)
           || (ea.getEventType() == osgGA::GUIEventAdapter::RELEASE && ea.getButton()==osgGA::GUIEventAdapter::RIGHT_MOUSE_BUTTON)
           ))
        return false;

    double u=0, v=0;
    switch (ea.getEventType()){
    case osgGA::GUIEventAdapter::PUSH:
        if (this->getRaytraceCanvasIntersection(ea,aa,u,v))
            this->doStroke(u, v, 0);
        break;
    case osgGA::GUIEventAdapter::RELEASE:
        if (this->getRaytraceCanvasIntersection(ea,aa,u,v))
            this->doStroke(u, v, 2);
        break;
    case osgGA::GUIEventAdapter::DRAG:
        if (this->getRaytraceCanvasIntersection(ea,aa,u,v))
            this->doStroke(u, v, 1);
        break;
    default:
        break;
    }
    return true;
}

void EventHandler::doStroke(double u, double v, int mouse)
{
    m_canvas->doStroke(u, v, mouse);
}

bool EventHandler::getRaytraceCanvasIntersection(const osgGA::GUIEventAdapter &ea, osgGA::GUIActionAdapter &aa, double &u, double &v)
{
    double x = ea.getX();
    double y = ea.getY();

    osgViewer::View* viewer = dynamic_cast<osgViewer::View*>(&aa);
    if (!viewer){
        std::cerr << "getRaytraceCanvasIntersection(): could not read viewer" << std::endl;
        return false;
    }

    osg::Camera* camera = viewer->getCamera();
    if (!camera){
        std::cout << "getRaytraceCanvasIntersection(): could not read camera" << std::endl;
        return false;
    }

    if (!camera->getViewport()){
        std::cerr << "getRaytraceIntersection(): could not read viewport" << std::endl;
        return false;
    }

    osg::Matrix VPW = camera->getViewMatrix()
            * camera->getProjectionMatrix()
            * camera->getViewport()->computeWindowMatrix();
    osg::Matrix invVPW;
    if (!invVPW.invert(VPW)){
        std::cerr << "getRaytraceIntersection(): could not invert View-projection-world matrix for ray casting" << std::endl;
        return false;
    }

    /* Algorithm:
    *  Calcualte near and far point in global 3D.
    *  Intersect that segment with plane of canvas - 3D intersection point.
    *  Extract local 3D coords so that to create a stroke.
    */

    osg::Vec3f nearPoint = osg::Vec3f(x, y, 0.f) * invVPW;
    osg::Vec3f farPoint = osg::Vec3f(x, y, 1.f) * invVPW;

    const osg::Plane plane = m_canvas->getPlane();
    const osg::Vec3f center = m_canvas->getCenter();

    std::vector<osg::Vec3f> ray(2);
    ray[0] = nearPoint;
    ray[1] = farPoint;
    if (plane.intersect(ray)){ // 1 or -1: no intersection
        std::cerr << "getRaytraceIntersection(): no intersection with the ray." << std::endl;
        return false;
    }

    osg::Vec3f dir = farPoint-nearPoint;
    if (! plane.dotProductNormal(dir)){ // denominator
        std::cerr << "getRaytraceIntersection(): projected line is parallel to the canvas plane" << std::endl;
        return false;
    }
    if (! plane.dotProductNormal(center-nearPoint)){
        std::cerr << "getRaytraceIntersection(): plane contains the line, so no single intersection can be defined" << std::endl;
        return false;
    }

    double len = plane.dotProductNormal(center-nearPoint) / plane.dotProductNormal(dir);
    osg::Vec3f P = dir * len + nearPoint; // global 3D intersection

    osg::Matrix M =  m_canvas->getTransform()->getMatrix();
    osg::Matrix invM;
    if (!invM.invert(M)){
        std::cerr << "getRaytraceIntersection(): could not invert model matrix" << std::endl;
        return false;
    }
    osg::Vec3f p = P * invM; // local intersection

    u=p.x();
    v=p.z();
    return true;
}

EventHandler.h

#ifndef EVENTHANDLER_H
#define EVENTHANDLER_H

#include <osg/observer_ptr>
#include <osgGA/GUIEventHandler>
#include <osgGA/GUIActionAdapter>
#include <osgGA/GUIEventAdapter>

#include "Canvas.h"

class EventHandler : public osgGA::GUIEventHandler
{
public:
    EventHandler(entity::Canvas* canvas);
    virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa);

    virtual void doStroke(double u, double v, int mouse);

protected:
    bool getRaytraceCanvasIntersection(const osgGA::GUIEventAdapter& ea,
                                       osgGA::GUIActionAdapter& aa,
                                       double& u, double& v);

private:
    osg::observer_ptr<entity::Canvas> m_canvas;
};

#endif // EVENTHANDLER_H

osg-raycast.cpp

/*
 * =====================================================================================
 *
 *       Filename:  osg-raycast.cpp
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  01/12/2016 07:50:06 PM
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Victoria Rudakova, vicrucann@gmail.com
 *   Organization:  vicrucann.github.io
 *
 * =====================================================================================
 */

#include <iostream>
#include <windows.h>

#include <osg/ref_ptr>
#include <osgViewer/Viewer>

#include "Canvas.h"
#include "Stroke.h"
#include "EventHandler.h"

int main(int, char**){

    ::SetProcessDPIAware();
    osg::ref_ptr<entity::Canvas> canvas = new entity::Canvas;
    osg::ref_ptr<EventHandler> EH = new EventHandler(canvas.get());

    osgViewer::Viewer viewer;
    viewer.setSceneData(canvas.get());
    viewer.addEventHandler(EH.get());
    viewer.setUpViewInWindow(100,100,300,300);

    osg::Camera* cam = viewer.getCamera();
    cam->setClearColor(osg::Vec4(1.0f, 1.0f, 1.0f, 0.f));
    cam->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    osg::StateSet* stateset = canvas->getOrCreateStateSet();
    stateset->setMode(GL_LINE_SMOOTH, osg::StateAttribute::ON);
    stateset->setMode(GL_BLEND, osg::StateAttribute::ON);
    stateset->setMode(GL_LIGHTING,osg::StateAttribute::OFF);

    return viewer.run();
}

Stroke.cpp

#include "Stroke.h"

entity::Stroke::Stroke()
    : osg::Geometry()
{
    osg::Vec3Array* vertices = new osg::Vec3Array;
    vertices->push_back(osg::Vec3(0,0,0));
    vertices->push_back(osg::Vec3(0.5,0,0.5));

    osg::Vec4 color = osg::Vec4(1,0,0,1);
    osg::Vec4Array* colors = new osg::Vec4Array;
    colors->push_back(color);
    colors->push_back(color);

    this->setVertexArray(vertices);
    this->setColorArray(colors);
    this->setColorBinding(osg::Geometry::BIND_OVERALL);
    this->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINE_STRIP, 0, 2));

    this->setDataVariance(osg::Object::DYNAMIC);
    this->setUseDisplayList(false);
    this->setUseVertexBufferObjects(true);
}

void entity::Stroke::setColor(const osg::Vec4 &c)
{
    osg::Vec4Array* colors = static_cast<osg::Vec4Array*>(this->getColorArray());
    colors->front() = c;
    colors->dirty();
}

void entity::Stroke::setBegin(float a, float b)
{
    osg::Vec3Array* verts = static_cast<osg::Vec3Array*>(this->getVertexArray());
    (*verts)[0] = osg::Vec3(a,0,b);
    verts->dirty();
}

void entity::Stroke::setEnd(float c, float d)
{
    osg::Vec3Array* verts = static_cast<osg::Vec3Array*>(this->getVertexArray());
    (*verts)[1] = osg::Vec3(c,0,d);
    verts->dirty();
}

void entity::Stroke::setBeginEnd(float a, float b, float c, float d)
{
    osg::Vec3Array* verts = static_cast<osg::Vec3Array*>(this->getVertexArray());
    if (verts->size() == 0) {
        verts->push_back(osg::Vec3(a,0,b));
        verts->push_back(osg::Vec3(c,0,d));
    }
    else {
        (*verts)[0] = osg::Vec3(a,0,b);
        (*verts)[1] = osg::Vec3(c,0,d);
    }

    verts->dirty();
}

entity::Stroke::~Stroke()
{
}

Stroke.h

#ifndef STROKE_H
#define STROKE_H

#include <osg/Geometry>

namespace entity{
class Stroke : public osg::Geometry
{
public:
    Stroke();

    void setColor(const osg::Vec4& c);
    void setBegin(float a, float b);
    void setEnd(float c, float d);
    void setBeginEnd(float a, float b, float c, float d);
protected:
    ~Stroke();
}; // class
} // namespace

#endif // STROKE_H