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hadichko
08-16-2017, 07:34 AM
Hi,

I am trying to display an extruded circle using OpenGL and the glut library under Windows and Visual C++. The final surface should look like a perfectly round tube. However, what I see on the display is rather a jagged "tube", see attached. The code, I am using for this purpose, is attached. I appreciate any hint to solve this issue.

Thank you!

Hadi

2452


#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <GL/freeglut.h>
#include <cstdio>
#include <iostream>
using namespace std;

#define S_NUMPOINTS 9
#define S_ORDER 3
#define S_NUMKNOTS (S_NUMPOINTS + S_ORDER)
#define T_NUMPOINTS 2
#define T_ORDER 2
#define T_NUMKNOTS (T_NUMPOINTS + T_ORDER)
#define SQRT2 1.414213
#define SQRT2HALF 0.707107


/* initialized local data */

GLfloat sknots[S_NUMKNOTS] =
{ 0., 0., 0., 1., 1., 2., 2., 3., 3., 4., 4., 4. };
GLfloat tknots[T_NUMKNOTS] =
{ 0.0, 0.0, 1.0, 1.0 };

GLfloat ctlpoints[S_NUMPOINTS][T_NUMPOINTS][4] =
{
{ { 1.0, 0.0, 1.0, 1.0 }, { 1.0, 0.0, 0.0, 1.0 } },
{ { 1.0, 1.0, 1.0, SQRT2HALF },{ 1.0, 1.0, 0.0, SQRT2HALF } },
{ { 0.0, 1.0, 1.0, 1.0 },{ 0.0, 1.0, 0.0, 1.0 } },
{ { -1.0, 1.0, 1.0, SQRT2HALF },{ -1.0, 1.0, 0.0, SQRT2HALF } },
{ { -1.0, 0.0, 1.0, 1.0 },{ -1.0, 0.0, 0.0, 1.0 } },
{ { -1.0, -1.0, 1.0, SQRT2HALF },{ -1.0, -1.0, 0.0, SQRT2HALF } },
{ { 0.0, -1.0, 1.0, 1.0 },{ 0.0, -1.0, 0.0, 1.0 } },
{ { 1.0, -1.0, 1.0, SQRT2HALF },{ 1.0, -1.0, 0.0, SQRT2HALF } },
{ { 1.0, 0.0, 1.0, 1.0 },{ 1.0, 0.0, 0.0, 1.0 } },
};

GLUnurbsObj *theNurb;

/* Initialize material property, light source, lighting model,
* and depth buffer.
*/
void myinit(void)
{
GLfloat mat_ambient[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_diffuse[] = { 1.0, 0.2, 1.0, 1.0 };
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_shininess[] = { 50.0 };

GLfloat light0_position[] = { 1.0, 0.1, 1.0, 0.0 };
GLfloat light1_position[] = { -1.0, 0.1, 1.0, 0.0 };

GLfloat lmodel_ambient[] = { 0.3, 0.3, 0.3, 1.0 };

glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
glLightfv(GL_LIGHT0, GL_POSITION, light0_position);
glLightfv(GL_LIGHT1, GL_POSITION, light1_position);
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);

glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHT1);
glDepthFunc(GL_LESS);
glEnable(GL_DEPTH_TEST);
glEnable(GL_AUTO_NORMAL);

theNurb = gluNewNurbsRenderer();

gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 25.0);
gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_FILL);
}

void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glPushMatrix();
glTranslatef(4., 4.5, 2.5);
glRotatef(220.0, 1., 0., 0.);
glRotatef(115.0, 0., 1., 0.);
glTranslatef(-4., -4.5, -2.5);

gluBeginSurface(theNurb);
gluNurbsSurface(theNurb,
S_NUMKNOTS, sknots,
T_NUMKNOTS, tknots,
4 * T_NUMPOINTS,
4,
&ctlpoints[0][0][0],
S_ORDER, T_ORDER,
GL_MAP2_VERTEX_4);
gluEndSurface(theNurb);

glPopMatrix();
glFlush();
}

void myReshape(int w, int h)
{
w = 400;
h = 400;
glViewport(100, 100, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-1.0, 1.0, -1.5, 0.5, 0.8, 10.0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(7.0, 4.5, 4.0, 4.5, 4.5, 2.0, 6.0, -3.0, 2.0);
}

/* Main Loop
* Open window with initial window size, title bar,
* RGBA display mode, and handle input events.
*/
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow(argv[0]);
myinit();
glutReshapeFunc(myReshape);
glutDisplayFunc(display);
glutMainLoop();

return 0; /* ANSI C requires main to return int. */
}