OpenGL/GLUT cylinder and cone

This is a discussion on OpenGL/GLUT cylinder and cone within the Game Programming forums, part of the General Programming Boards category; I have been playing around with a piece of code for a cylinder in GLUT or OpenGL and using Vertices ...

  1. #1
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    OpenGL/GLUT cylinder and cone

    I have been playing around with a piece of code for a cylinder in GLUT or OpenGL and using Vertices instead of pre-forms and the resulting code is below.

    It is also capable of producing a cone and an offset cone with a small amount of modification. I hope that it will be of help to someone.

    I apologise in advance if my identation is out but I cut and pasted various bits and changed other bits some many times that all correct layout went completely by the end.

    I'm not sure how useful it will be for texture mapping as I haven't learnt that yet.


    Code:
    glBegin( GL_TRIANGLE_FAN );
        glNormal3f(0.0f,1.0f,0.0f);
        //change y value here and in the vertex below to move the end up or
        // down to seal the top end of the cylinder
        glVertex3f(0.0f,6,0.0f);
        for(i=0;i<=300;i++)
        {
            glVertex3f(2*cos(-i),6,2*sin(-i));
        }
    
        glEnd();
    // bottom end of cylinder
        glBegin( GL_TRIANGLE_FAN );
        glNormal3f(0.0f,-1.0f,0.0f);
        //change y value here and in the vertex below to move the end up or
        // down to seal the bottom end of the cylinder. Delete for a cone
        glVertex3f(0.0f,-0,0.0f);
        for(i=0;i<=300;i++)
        {
            glVertex3f(2*cos(i),0,2*sin(i));
        }
    
        glEnd();
    
    //side of cylinder, y-values are used for the length of the cylinder
    //x and z values are used for the radius.
    // for a cone change y values to integers for the length.
        for(j=0;j<=45;j++){
                            glBegin(GL_QUAD_STRIP);
                            for(i=0;i<300;i++){
    
                            glNormal3f(2*cos(i), 0.0f, 2*sin(i));
    
    //  for a cone change the x and z values to 0 for a central cone or other integers for an offset cone
    // don't forget to delete the bottom end circle above.
    
                            glVertex3f(2*cos(i), (j)/7, 2*sin(i));
                            glVertex3f(2*cos(i), (j+1)/7, 2*sin(i));
                            }
        }
        glEnd();

  2. #2
    Programming Wraith GReaper's Avatar
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    GLU with its optimized support for quadrics can be very useful at drawing various shapes. Look it up.
    Devoted my life to programming...

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    I tried it and eventually got it to work with quadrics and not crashing out codeblocks but I also tried this an alternative for more flexibility and no quadrics. Also for some reason I can't draw a cylinder in OpenGL without having the sphere in it as well. I must of done something wrong somewhere.
    Also OpenGL won't draw an offset cone.

    I'm trying to work on a sphere after I complete a ball bearing clock in GLUT.

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    Programming Wraith GReaper's Avatar
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    Quote Originally Posted by software tester View Post
    Also for some reason I can't draw a cylinder in OpenGL without having the sphere in it as well.
    What do you mean by that?
    Devoted my life to programming...

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    Quote Originally Posted by Sipher View Post
    What do you mean by that?
    Not entirely sure yet but I set up the quadrics etc and when I enter
    gluSphere(quadric*, radius, stacks, slices); I get a sphere.

    However if I change this to gluCylinder(quadric*, base, top, hieght, stacks, slices);

    It compiles but doesn't show a cylinder when running.

    I'll have a look at it again later.

    Also the above method should with a couple of changes bend the cylinder form into a partial torus without using Clip Planes.

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