CODEWITHSUNDEEP
opengllinecube
Alexander
Alexander

Reputation: 19

Draw 3D cube with line loop

I had faced the problem of using a line loop to draw out a 3D cube by using open gl.

void cube1()
{
    glBegin(GL_LINE_LOOP);

    //Cube1
    //Face1
    glColor3f(1.0, 0.0, 0.0);
    glVertex3f(-0.1, 0, 0);
    glVertex3f(0.4, 0, 0);
    glVertex3f(0.4, -0.3, 0);
    glVertex3f(-0.1, -0.3, 0);

    //Face2
    glColor3f(1.0, 1.0, 0.0);
    glVertex3f(-0.1, -0.3, 0);
    glVertex3f(-0.1, -0.3, 1);
    glVertex3f(-0.1, 0, 1);
    glVertex3f(-0.1, 0, 0);

    //Face3
    glColor3f(1.0, 0.0, 1.0);
    glVertex3f(-0.1, 0, 0);
    glVertex3f(-0.1, 0, 1);
    glVertex3f(0.4, 0, 1);
    glVertex3f(0.4, 0, 0);

    //Face4
    glColor3f(0.0, 1.0, 1.0);
    glVertex3f(0.4, 0, 0);
    glVertex3f(0.4, 0, 1);
    glVertex3f(0.4, -0.3, 1);
    glVertex3f(0.4, -0.3, 0);

    //Face5
    glColor3f(0.0, 1.0, 0.0);
    glVertex3f(0.4, -0.3, 0);
    glVertex3f(-0.1, -0.3, 0);
    glVertex3f(-0.1, -0.3, 1);
    glVertex3f(0.4, -0.3, 1);

    //Face6
    glColor3f(0.0, 0.0, 1.0);
    glVertex3f(0.4, -0.3, 1);
    glVertex3f(-0.1, -0.3, 1);
    glVertex3f(-0.1, 0, 1);
    glVertex3f(0.4, 0, 1);

    glEnd();
}

However, I still could not form the correct shape for my cube.Below are my output. Can anyone know the solution?

Cube

Upvotes: 1

Views: 588

Answers (1)

Rabbid76
Rabbid76

Reputation: 210908

A line loop is an endless primitive. It behaves differently from GL_QUADS or GL_TRIANGLES (see OpenGL - Primitive). Therefore, you must draw 6 separate line loops (or at least 4). One for each side:

//Face1
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINE_LOOP);
glVertex3f(-0.1, 0, 0);
glVertex3f(0.4, 0, 0);
glVertex3f(0.4, -0.3, 0);
glVertex3f(-0.1, -0.3, 0);
glEnd();
    
//Face2
glColor3f(1.0, 1.0, 0.0);
glBegin(GL_LINE_LOOP);
glVertex3f(-0.1, -0.3, 0);
glVertex3f(-0.1, -0.3, 1);
glVertex3f(-0.1, 0, 1);
glVertex3f(-0.1, 0, 0);
glEnd();

// [...]

Upvotes: 1

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