OpenGL: new window displays content of the current window opened - c++

Question

I tried to draw Bezier surface using OpenGL. My program reads an input file with number of sample points for plot, control points and color palette for surface coloring. It must output a new window with surface plot where I can manipulate properties of surface and control points.
Points generated from Bernstein polynomial are triangulated and assigned a color by color palette by mapping it from minimum and maximum height of triangles.
Unfortunately, it opens a window with a portion of the current window opened in OS without creating a new interface for surface.
Here is the code:
#include <iostream>
#include <vector>
#include <string>
#include <fstream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <cmath>
using namespace std;
struct vertex
{
float x;
float y;
float z;
};
struct RGB
{
float r;
float g;
float b;
};
int main_window;
bool TM = true;
vertex surfaceTranslate;
float surfaceRotate = 0;
vertex camera;
vertex up;
int currentPointX = 0, currentPointY = 0;
vertex toY;
int SampleR, SampleC;
int M, N;
int K;
vector < vector <vertex> > points;
vector <RGB> palette;
vector < vector <vertex> > control;
float minH, maxH;
int fact (int n)
{
if (!n || n == 1)
{
return 1;
}
return n * fact (n - 1);
}
int C (int n, int i)
{
return fact (n) / (fact (i) * fact (n - i));
}
void initialDisplay(void)
{
glClearColor (1.0, 1.0, 1.0, 1.0);
glDisable (GL_LIGHTING);
glEnable (GL_RESCALE_NORMAL);
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPerspective (60, 1, 1, 1000000);
glMatrixMode (GL_MODELVIEW);
glLoadIdentity();
}
void updateControl()
{
control.clear();
for (int i = 0; i < SampleR; ++i)
{
vector <vertex> temp;
for (int j = 0; j < SampleC; ++j)
{
float u = (float)(i) / (SampleR - 1);
float v = (float)(j) / (SampleC - 1);
vertex p;
p.x = p.y = p.z = 0;
for (int k = 0; k < M; ++k)
{
for (int m = 0; m < N; ++m)
{
float B_u = float (C (M - 1, k)) * pow (u, k) * pow (1 - u, M - 1 - k);
float B_v = float (C (N - 1, m)) * pow (v, m) * pow (1 - v, N - 1 - m);
p.x += B_u * B_v * points[k][m].x;
p.y += B_u * B_v * points[k][m].y;
p.z += B_u * B_v * points[k][m].z;
}
}
temp.push_back (p);
}
control.push_back (temp);
}
maxH = 1 << ((sizeof(float) * 8) - 1);
minH = -maxH;
for (int i = 0; i < SampleR - 1; ++i)
{
for (int j = 0; j < SampleC - 1; ++j)
{
float h = (control[i][j].y + control[i + 1][j].y + control[i][j + 1].y) / 3;
if (h > maxH)
{
maxH = h;
}
if (h < minH)
{
minH = h;
}
h = (control[i][j + 1].y + control[i + 1][j].y + control[i + 1][j + 1].y) / 3;
if (h > maxH)
{
maxH = h;
}
if (h < minH)
{
minH = h;
}
}
}
for (int i = 0; i < SampleR; ++i)
{
for (int j = 0; j < SampleC; ++j)
{
toY.x += control[i][j].x;
toY.z += control[i][j].z;
}
toY.x /= SampleR * SampleC;
toY.z /= SampleR * SampleC;
}
}
void display(void)
{
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluLookAt (camera.x, camera.y, camera.z, 0, 0, 0, up.x, up.y, up.z);
glTranslatef (surfaceTranslate.x, surfaceTranslate.y, surfaceTranslate.z);
glTranslatef (toY.x, toY.y, toY.z);
glRotatef (surfaceRotate, 0, 1, 0);
glTranslatef (- toY.x, -toY.y, -toY.z);
if (!TM)
{
glPointSize (10);
glBegin (GL_POINTS);
for (int i = 0; i < M; ++i)
{
for (int j = 0; j < N; ++j)
{
if (i == currentPointX && j == currentPointY)
{
glColor3f (1.0, 0.0, 0.0);
}
else
{
glColor3f (0.0, 0.0, 1.0);
}
glVertex3f (points[i][j].x, points[i][j].y, points[i][j].z);
}
}
glEnd();
}
glBegin (GL_TRIANGLES);
for (int i = 0; i < SampleR - 1; ++i)
{
for (int j = 0; j < SampleC - 1; ++j)
{
glVertex3f (control[i][j].x, control[i][j].y, control[i][j].z);
glVertex3f (control[i + 1][j].x, control[i + 1][j].y, control[i + 1][j].z);
glVertex3f (control[i][j + 1].x, control[i][j + 1].y, control[i][j + 1].z);
float h = (control[i][j].y + control[i + 1][j].y + control[i][j + 1].y) / 3;
int r = (palette[K - 1].r - palette[0].r) * (h - minH) / (maxH - minH);
int g = (palette[K - 1].g - palette[0].g) * (h - minH) / (maxH - minH);
int b = (palette[K - 1].b - palette[0].b) * (h - minH) / (maxH - minH);
glColor3f (palette[r].r / (palette[K - 1].r - palette[0].r), palette[g].g / (palette[K - 1].g - palette[K - 1].g), palette[b].b / (palette[K - 1].b - palette[0].b));
glVertex3f (control[i + 1][j].x, control[i + 1][j].y, control[i + 1][j].z);
glVertex3f (control[i][j + 1].x, control[i][j + 1].y, control[i][j + 1].z);
glVertex3f (control[i + 1][j + 1].x, control[i + 1][j + 1].y, control[i + 1][j + 1].z);
h = (control[i + 1][j].y + control[i][j + 1].y + control[i + 1][j + 1].y) / 3;
r = (palette[K - 1].r - palette[0].r) * (h - minH) / (maxH - minH);
g = (palette[K - 1].g - palette[0].g) * (h - minH) / (maxH - minH);
b = (palette[K - 1].b - palette[0].b) * (h - minH) / (maxH - minH);
glColor3f (palette[r].r / (palette[K - 1].r - palette[0].r), palette[g].g / (palette[K - 1].g - palette[K - 1].g), palette[b].b / (palette[K - 1].b - palette[0].b));
}
}
glEnd();
}
void keyboardEvent (unsigned char key, int x, int y)
{
if (TM)
{
switch (key)
{
case ('2'):
TM = false;
glutSetWindowTitle ("Surface Editing Mode");
break;
case ('q'):
--surfaceTranslate.x;
break;
case ('w'):
++surfaceTranslate.x;
break;
case ('a'):
--surfaceTranslate.y;
break;
case ('s'):
++surfaceTranslate.y;
break;
case ('z'):
--surfaceTranslate.z;
break;
case ('x'):
++surfaceTranslate.z;
break;
case ('r'):
++surfaceRotate;
break;
case ('t'):
--surfaceRotate;
break;
}
}
else
{
switch (key)
{
case ('1'):
TM = true;
glutSetWindowTitle ("Transformation Mode");
break;
case ('q'):
--points[currentPointX][currentPointY].x;
updateControl();
break;
case ('w'):
++points[currentPointX][currentPointY].x;
updateControl();
break;
case ('a'):
--points[currentPointX][currentPointY].y;
updateControl();
break;
case ('s'):
++points[currentPointX][currentPointY].y;
updateControl();
break;
case ('z'):
--points[currentPointX][currentPointY].z;
updateControl();
break;
case ('x'):
++points[currentPointX][currentPointY].z;
updateControl();
break;
case ('i'):
if (!(SampleR % 2))
{
SampleR /= 2;
updateControl();
}
break;
case ('o'):
SampleR *= 2;
updateControl();
break;
case ('k'):
if (!(SampleC % 2))
{
SampleC /= 2;
updateControl();
}
break;
case ('l'):
SampleC *= 2;
updateControl();
break;
case (GLUT_KEY_UP):
if (currentPointY < N - 1)
{
++currentPointY;
}
break;
case (GLUT_KEY_DOWN):
if (currentPointY)
{
--currentPointY;
}
break;
case (GLUT_KEY_LEFT):
if (currentPointX)
{
--currentPointX;
}
break;
case (GLUT_KEY_RIGHT):
if (currentPointX < M - 1)
{
++currentPointX;
}
break;
}
}
glutPostRedisplay();
}
void changeDirection (int x, int y)
{
float dist = sqrt (pow (camera.x, 2) + pow (camera.y, 2) + pow (camera.z, 2));
camera.x = dist * sin (360.0 / 800 * x * 0.0174532) * sin (360.0 / 800 * y * 0.0174532);
camera.y = dist * cos (360.0 / 800 * y * 0.0174532);
camera.z = dist * cos (360.0 / 800 * x * 0.0174532) * sin (360.0 / 800 * y * 0.0174532);
up.x = dist * sin (360.0 / 800 * x * 0.0174532) * sin (360.0 / 800 * y * 0.0174532 - 1) - camera.x;
up.y = dist * cos (360.0 / 800 * y * 0.0174532 - 1) - camera.y;
up.z = dist * cos (360.0 / 800 * x * 0.0174532) * sin (360.0 / 800 * y * 0.0174532 - 1) - camera.z;
glutPostRedisplay();
}
void mouseEvent (int key, int state, int x, int y)
{
if (key == GLUT_KEY_LEFT)
{
changeDirection (x, y);
}
}
void readFile (char *fname)
{
ifstream file (fname);
if (file.is_open())
{
file >> SampleR >> SampleC;
file >> M >> N;
for (int i = 0; i < M; ++i)
{
vector <vertex> tempv;
for (int j = 0; j < N; ++j)
{
vertex temp;
file >> temp.x >> temp.y >> temp.z;
tempv.push_back (temp);
}
points.push_back (tempv);
}
file >> K;
for (int i = 0; i < K; ++i)
{
RGB temp;
file >> temp.r >> temp.g >> temp.b;
palette.push_back (temp);
}
}
file.close();
}
int main (int argc, char *argv[])
{
surfaceTranslate.x = surfaceTranslate.y = surfaceTranslate.z = toY.x = toY.y = toY.z = up.x = up.z = 0;
up.y = 1;
camera.x = camera.y = camera.z = 100;
readFile (argv[1]);
updateControl();
glutInit (&argc,argv);
glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowPosition (50, 50);
glutInitWindowSize (800, 800);
main_window = glutCreateWindow ("Transformation Mode");
glutDisplayFunc (display);
glutKeyboardFunc (keyboardEvent);
glutMouseFunc (mouseEvent);
glutMotionFunc (changeDirection);
initialDisplay();
glutMainLoop();
}

Answer 1

You're missing the call to glutSwapBuffers() at the end of your display() function. This is needed to display the frame when using double buffered rendering.