camera flickers during move

#include <iostream>
#include <osgViewer/Viewer>
#include <osg/Node>
#include <osgDB/ReadFile>
#include <osgUtil/LineSegmentIntersector>
#include <osgGA/TrackballManipulator> // Added header
#include <osgGA/FirstPersonManipulator> // Added header

#include <SDL2/SDL.h>

//g++ main.cpp -lSDL2 -lSDL2_image -lSDL2_ttf -losg -losgUtil -losgDB -losgViewer -losgGA -lGL -losgText

osg::Node* createModel(const std::string& filename) {
    osg::ref_ptr<osg::Node> loadedModel = osgDB::readNodeFile(filename);
    if (!loadedModel) {
        std::cerr << "Failed to load model file: " << filename << std::endl;
        return nullptr;
    }
    return loadedModel.release();
}

int main(int argc, char** argv) {
    // Initialize SDL
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        std::cerr << "SDL could not initialize! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    // Create an SDL window
    SDL_Window* window = SDL_CreateWindow("OpenSceneGraph with SDL2", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 800, 600, SDL_WINDOW_OPENGL);
    if (!window) {
        std::cerr << "Window could not be created! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    // Create an SDL OpenGL context
    SDL_GLContext gl_context = SDL_GL_CreateContext(window);
    if (!gl_context) {
        std::cerr << "OpenGL context could not be created! SDL_Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    // Load COLLADA model
    osg::Node* modelNode = createModel("test.3ds");
    if (!modelNode) {
        std::cerr << "Failed to load model!" << std::endl;
        return 1;
    }

    // Initialize OpenSceneGraph viewer
    osgViewer::Viewer viewer;

    // Create a root node
    osg::ref_ptr<osg::Group> root = new osg::Group;
    root->addChild(modelNode);

    // Set up the viewer
    viewer.setSceneData(root);
    viewer.setCameraManipulator(new osgGA::FirstPersonManipulator);
     viewer.realize();
    // Main loop
    while (!viewer.done()) {
           glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

       // osg::Vec3d moveDirection = keyboardEventHandler->getMoveDirection();
      osg::Vec3d moveDirection = osg::Vec3d(0,0,0.1);
      osg::Matrixd viewMatrix = viewer.getCameraManipulator()->getInverseMatrix();
      osg::Vec3d forwardVector = -osg::Matrixd::transform3x3(osg::Vec3d(0.0, 0.0, -1.0), viewMatrix);
      osg::Vec3d strafeVector = osg::Matrixd::transform3x3(osg::Vec3d(1.0, 0.0, 0.0), viewMatrix);

      osg::Vec3d eye = viewer.getCameraManipulator()->getMatrix().getTrans();
      eye += forwardVector * moveDirection.z() * 0.1; // Move forward/backward
      eye += strafeVector * moveDirection.x() * 0.1; // Move left/right

      osg::Vec3d center = eye + forwardVector;
      osg::Vec3d up = osg::Vec3d(0.0, 0.0, 1.0);
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

      osg::Matrixd viewMatrixNew;
      viewMatrixNew.makeLookAt(eye, center, up);

      viewer.getCameraManipulator()->setByMatrix(viewMatrixNew);
    //  viewer.getCameraManipulator()->setHomePosition(viewMatrixNew);
        // Render the scene
        viewer.frame();
        // Swap buffers
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

           SDL_GL_SwapWindow(window);

        // Handle SDL events
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
                case SDL_QUIT:
                    viewer.setDone(true);
                    break;
                case SDL_MOUSEBUTTONDOWN:
                    if (event.button.button == SDL_BUTTON_LEFT) {
                        int mouseX = event.button.x;
                        int mouseY = event.button.y;

                        // Perform collision detection with mouse
                        osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector = new osgUtil::LineSegmentIntersector(osgUtil::Intersector::WINDOW, mouseX, mouseY);
                        osgUtil::IntersectionVisitor iv(intersector);
                        viewer.getCamera()->accept(iv);

                        if (intersector->containsIntersections()) {
                            osgUtil::LineSegmentIntersector::Intersection intersection = *(intersector->getIntersections().begin());
                         //   std::cout << "Collision detected at point: " << intersection.getWorldIntersectPoint() << std::endl;
                        } else {
                            std::cout << "No collision detected." << std::endl;
                        }
                    }
                    break;
            case SDL_KEYDOWN:
                // Camera movement with WASD keys
                switch (event.key.keysym.sym) {
                    case SDLK_w: // Move forward
                    //    viewer.getCameraManipulator()->forward(0.1);
                        break;
                    case SDLK_s: // Move backward
                    //    viewer.getCameraManipulator()->backward(0.1);
                        break;
                    case SDLK_a: // Strafe left
                    //    viewer.getCameraManipulator()->left(0.1);
                        break;
                    case SDLK_d: // Strafe right
                    //    viewer.getCameraManipulator()->right(0.1);
                        break;
                    default:
                        break;
                }
                break;
                default:
                    break;
            }
        }

        SDL_Delay(10);

    }

    // Cleanup
    SDL_GL_DeleteContext(gl_context);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}
openscenegraph / OpenSceneGraph

camera flickers during move #1318
