Trying to draw a lot of points. But the problem is that I do not know how to draw the points so that at the initial moment of time they all fall on the screen. Another problem with the approximation and rotation, I do not understand how to do this relative to the center of the bounding box or screen. I ask for your help.

BoundingBox.h

#include "vector3d.h" class BoundingBox { public: BoundingBox() : valid(false) {} void add(Vector3D aPoint) { if (valid) { if (aPoint.x < minCorner.x) minCorner.x = aPoint.x; else if (aPoint.x > maxCorner.x) maxCorner.x = aPoint.x; if (aPoint.y < minCorner.y) minCorner.y = aPoint.y; else if (aPoint.y > maxCorner.y) maxCorner.y = aPoint.y; if (aPoint.z < minCorner.z) minCorner.z = aPoint.z; else if (aPoint.z > maxCorner.z) maxCorner.z = aPoint.z; } else { maxCorner = minCorner = aPoint; valid = true; } } void clear() { valid = false; minCorner = maxCorner = Vector3D(0,0,0); } Vector3D getCenter() { return Vector3D((minCorner.x + maxCorner.x) * 0.5, (minCorner.y + maxCorner.y) * 0.5, (minCorner.z + maxCorner.z) * 0.5); } public: Vector3D minCorner; Vector3D maxCorner; bool valid; };

Vector3D.h

 class Vector3D { public: Vector3D(double x1 = 0, double y1 = 0, double z1 = 0) : x(x1), y(y1), z(z1) {} double x, y, z; };

glwidget.h

 #include <QGLWidget> #include <vector> #include "vector3d.h" class GLWidget : public QGLWidget { public: GLWidget(QWidget* parent = NULL); ~GLWidget() {} protected: void initializeGL(); void paintGL(); void resizeGL( int w, int h ); public slots: void mousePressEvent( QMouseEvent* event ); void mouseMoveEvent( QMouseEvent* event ); void wheelEvent(QWheelEvent* pe) ; private: GLfloat xRot, yRot, zRot, scale, xTrans, yTrans, zTrans; QPoint lastPos; std::vector<Vector3D> m_points; };

glwidget.cpp

 #include "glwidget.h" #include "boundingbox.h" #include <cstdlib> #include <ctime> #include <cmath> #include <QMouseEvent> double random(double min, double max) { return (double)(rand())/RAND_MAX*(max - min) + min; } GLWidget::GLWidget(QWidget *parent) : QGLWidget(parent) { std::srand(std::time(NULL)); for(int i = 0; i < 1024; i++) { Vector3D V; Vx = random(1000.0,10000.0); Vy = random(1000.0,10000.0); Vz = random(1000.0,10000.0); m_points.push_back(V); } xRot = yRot = zRot = xTrans = yTrans = zTrans = 0.0; scale = 1.0; } void GLWidget::initializeGL() { glClearColor( 0.0, 0.0, 0.0, 0.0); glShadeModel( GL_SMOOTH ); glEnable(GL_DEPTH_TEST); } void GLWidget::paintGL() { BoundingBox bbox; for(int i = 0; i < m_points.size(); i++) bbox.add(m_points[i]); Vector3D boxC = bbox.getCenter(); glClearColor(0, 0, 0, 1); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); double dL = 100; glOrtho(bbox.minCorner.x - dL, bbox.maxCorner.x + dL, bbox.minCorner.y - dL, bbox.maxCorner.y + dL, bbox.minCorner.z - dL, bbox.maxCorner.z + dL); glScalef( scale, scale, scale ); glTranslatef(-boxC.x, 0, 0); glTranslatef(0, -boxC.y, 0); glTranslatef(0, 0, -boxC.z); glRotatef( xRot, 1.0, 0.0, 0.0 ); glRotatef( yRot, 0.0, 1.0, 0.0 ); glRotatef( zRot, 0.0, 0.0, 1.0 ); glTranslatef( -xTrans, 0.0, 0.0 ); glTranslatef( 0.0, yTrans, 0.0 ); glTranslatef( 0.0, 0.0, zTrans ); glBegin(GL_POINTS); glColor3f(1,1,1); for(unsigned i = 0; i < m_points.size(); i++) { Vector3D P = m_points[i]; glVertex3d(Px, Py, Pz); } glEnd(); } void GLWidget::resizeGL(int w, int h) { glViewport( 0, 0, (GLint)w, (GLint)h ); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 15.0 ); glMatrixMode( GL_MODELVIEW ); } void GLWidget::mousePressEvent(QMouseEvent *event) { lastPos = event->pos(); updateGL(); } void GLWidget::mouseMoveEvent( QMouseEvent* event ) { float dx = (event->pos().x()-lastPos.x()); float dy = (event->pos().y()-lastPos.y()); if(event->buttons() == Qt::LeftButton) { xRot += dy; yRot += dx; } else if(event->buttons() == Qt::RightButton) { xTrans -= dx/(1.0); yTrans -= dy/(1.0); } lastPos = event->pos(); updateGL(); } void GLWidget::wheelEvent(QWheelEvent* pe) { if ((pe->delta())>0) scale*=1.1; else if ((pe->delta())<0) scale/=1.1; updateGL(); }

    1 answer 1

    Possible solution obtained by the "finger to the sky" method

     void GLWidget::paintGL() { BoundingBox bbox; for(int i = 0; i < m_points.size(); i++) bbox.add(m_points[i]); Vector3D boxC = bbox.getCenter(); glClearColor(0, 0, 0, 1); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); double dL = 1000; double maxLen = std::max(std::max(bbox.maxCorner.x-bbox.minCorner.x, bbox.maxCorner.y-bbox.minCorner.y), bbox.maxCorner.z-bbox.minCorner.z); double f_scale = scale; if(scale < 1) f_scale = 1/scale; glOrtho(boxC.x-maxLen/1 - dL, boxC.x + maxLen/1 + dL, boxC.y-maxLen/1 - dL, boxC.y + maxLen/1 + dL, -(f_scale)*std::fabs(boxC.z-maxLen/1 - dL), f_scale*std::fabs(boxC.z + maxLen/1 + dL)); glTranslated(boxC.x, 0, 0); glTranslated(0, boxC.y, 0); glTranslated(0, 0, boxC.z); glScalef( scale, scale, scale ); glTranslated(-boxC.x, 0, 0); glTranslated(0, -boxC.y, 0); glTranslated(0, 0, -boxC.z); glTranslated(boxC.x-xTrans, 0, 0); glTranslated(0, boxC.y+yTrans, 0); glTranslated(0, 0, boxC.z+zTrans); glRotated( xRot, 1.0, 0.0, 0.0 ); glRotated( yRot, 0.0, 1.0, 0.0 ); glRotated( zRot, 0.0, 0.0, 1.0 ); glTranslated(-boxC.x+xTrans, 0, 0); glTranslated(0, -boxC.y-yTrans, 0); glTranslated(0, 0, -boxC.z-zTrans); glTranslated( -xTrans, 0.0, 0.0 ); glTranslated( 0.0, yTrans, 0.0 ); glTranslated( 0.0, 0.0, zTrans ); glBegin(GL_POINTS); glColor3f(1,1,1); for(unsigned i = 0; i < m_points.size(); i++) { Vector3D P = m_points[i]; glVertex3d(Px, Py, Pz); } glEnd(); }