C++: Removing Moire effect from openGL

Question

I draw patterns which have detailed pixels and they often face with Moire effect. I am not good at shading and I am not sure if this problem will be solved by shaders. I have not found any basic, understandable and complete example of shaders. Most of the tutorial websites start a program from the middle omitting the header file includes!

This is a MWE of my code. Is it possible to mitigate or remove the Moire effect from it?

#include <cmath>
#include <vector>

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

const int w=640,h=480;
float cam_angle=0.0f;

void init()
{
    GLfloat LightAmbient[] = { 0.2f, 0.2f, 0.2f, 1.0f };
    GLfloat LightDiffuse[] = { 0.5f, 0.5f, 0.5f, 1.0f };
    GLfloat LightPosition[] = { 5.0f, 5.0f, -10.0f, 1.0f };

    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
    glEnable(GL_DEPTH_TEST);
    glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);
    glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);
    glLightfv(GL_LIGHT1, GL_POSITION, LightPosition);
    glEnable(GL_LIGHT1);
}

void onDisplay()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective (90, float(w)/float(h), 0.01, 10000);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    const double pi=3.1415926;
    double cam_x=2.0*cos(pi/4.0)*cos(cam_angle);;
    double cam_y=2.0*sin(pi/4.0)*cos(cam_angle);;
    double cam_z=2.0*sin(cam_angle);
    gluLookAt(cam_x, cam_y, cam_z,  0, 0, 0, 0, 0, 1);

    struct Point3D
    {
        double x, y, z;
        unsigned char r, g, b, a=255;
    };

    for(double r=0.5;r<=1.0;r+=0.03)
    {
        std::vector<Point3D> points;
        for(int i=0;i<1000;i++)
        {
            double theta=double(i)/1000.0*pi*2.0;
            Point3D p;
            p.x=r*sin(theta);
            p.y=r*cos(theta);
            p.z=r;
            p.r=128;
            p.g=200;
            p.b=50;
            points.push_back(p);
        }
    // draw
        glPushMatrix();
        glColor3ub(255,255,255);
        glEnableClientState( GL_VERTEX_ARRAY );
        glEnableClientState( GL_COLOR_ARRAY );
        glVertexPointer(3, GL_DOUBLE, sizeof(Point3D), &points[0].x );
        glColorPointer( 4, GL_UNSIGNED_BYTE, sizeof(Point3D), &points[0].r );
        // glPointSize( 3.0 );
        glLineWidth(2.0);
        glDrawArrays( GL_LINE_STRIP, 0, int(points.size()) );
        glDisableClientState( GL_VERTEX_ARRAY );
        glDisableClientState( GL_COLOR_ARRAY );
        glPopMatrix();
    }

    glFlush();
    glutSwapBuffers();
}

void Timer(int /*value*/)
{
    cam_angle+=0.01f;
    glutPostRedisplay();
    // 100 milliseconds
    glutTimerFunc(100, Timer, 0);
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitWindowSize (w, h);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
    glutInitWindowPosition (100, 100);
    glutCreateWindow ("my window");
    glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_BLEND);

    init();
    glutDisplayFunc(onDisplay);
    Timer(0);
    glutMainLoop();

    return 0;
}

Answer 1

If you use Multisampling, then the result will be significantly improved:

glutSetOption(GLUT_MULTISAMPLE, 8);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE | GLUT_MULTISAMPLE);

without GLUT_MULTISAMPLE:

with GLUT_MULTISAMPLE:

See also the answer to GLUT + OpenGL multisampling anti aliasing (MSAA)