I am using SharpGL library.

The following source code draws several hundred solid spheres at various locations -

// Initialization routine.
        void setup()
        {
            gl.ClearColor(0.0f, 0.0f, 0.0f, 0.0f);
            gl.Enable(OpenGL.GL_DEPTH_TEST); // Enable depth testing.

            // Turn on OpenGL lighting.
            gl.Enable(OpenGL.GL_LIGHTING);

            // Light property vectors.
            float []lightAmb = { 0.0f, 0.0f, 0.0f, 1.0f };
            float[]lightDifAndSpec0 = { 1.0f, 1.0f, 1.0f, 1.0f };
            float[]lightDifAndSpec1 = { 0.0f, 1.0f, 0.0f, 1.0f };
            float[]globAmb = { 0.2f, 0.2f, 0.2f, 1.0f };

            // Light0 properties.
            gl.Light(OpenGL.GL_LIGHT0, OpenGL.GL_AMBIENT, lightAmb);
            gl.Light(OpenGL.GL_LIGHT0, OpenGL.GL_DIFFUSE, lightDifAndSpec0);
            gl.Light(OpenGL.GL_LIGHT0, OpenGL.GL_SPECULAR, lightDifAndSpec0);

            // Light1 properties.
            gl.Light(OpenGL.GL_LIGHT1, OpenGL.GL_AMBIENT, lightAmb);
            gl.Light(OpenGL.GL_LIGHT1, OpenGL.GL_DIFFUSE, lightDifAndSpec1);
            gl.Light(OpenGL.GL_LIGHT1, OpenGL.GL_SPECULAR, lightDifAndSpec1);

            gl.Enable(OpenGL.GL_LIGHT0); // Enable particular light source.
            gl.Enable(OpenGL.GL_LIGHT1); // Enable particular light source.
            gl.LightModel(OpenGL.GL_LIGHT_MODEL_AMBIENT, globAmb); // Global ambient light.
            gl.LightModel(OpenGL.GL_LIGHT_MODEL_LOCAL_VIEWER, OpenGL.GL_TRUE); // Enable local viewpoint

            // Cull back faces.
            gl.Enable(OpenGL.GL_CULL_FACE);
            gl.CullFace(OpenGL.GL_BACK);
        }

        //http://www.java2s.com/example/java/javax.media.opengl/opengl-method-to-draw-a-sphere-in-opengl.html
        void drawSphere(Point3d c, double r, int n)
        {
            int i, j;
            double theta1, theta2, theta3;
            Point3d e = new Point3d();
            Point3d p = new Point3d();

            if (c == null)
            {
                c = new Point3d(0, 0, 0);
            }//from w ww  .j  ava2 s .  c o m

            double twoPi = Math.PI * 2;
            double piD2 = Math.PI / 2;
            if (r < 0)
                r = -r;
            if (n < 0)
                n = -n;
            if (n < 4 || r <= 0)
            {
                gl.Begin(OpenGL.GL_POINTS);
                gl.Vertex(c.X, c.Y, c.Z);
                gl.End();
                return;
            }

            for (j = 0; j < n / 2; j  )
            {
                theta1 = j * twoPi / n - piD2;
                theta2 = (j   1) * twoPi / n - piD2;

                gl.Begin(OpenGL.GL_QUAD_STRIP);
                //            gl.glBegin(GL.GL_TRIANGLE_STRIP);
                for (i = 0; i <= n; i  )
                {
                    theta3 = i * twoPi / n;

                    e.X = Math.Cos(theta2) * Math.Cos(theta3);
                    e.Y = Math.Sin(theta2);
                    e.Z = Math.Cos(theta2) * Math.Sin(theta3);
                    p.X = c.X   r * e.X;
                    p.Y = c.Y   r * e.Y;
                    p.Z = c.Z   r * e.Z;

                    gl.Normal(e.X, e.Y, e.Z);
                    gl.TexCoord(i / (double)n, 2 * (j   1) / (double)n);
                    gl.Vertex(p.X, p.Y, p.Z);

                    e.X = Math.Cos(theta1) * Math.Cos(theta3);
                    e.Y = Math.Sin(theta1);
                    e.Z = Math.Cos(theta1) * Math.Sin(theta3);
                    p.X = c.X   r * e.X;
                    p.Y = c.Y   r * e.Y;
                    p.Z = c.Z   r * e.Z;

                    gl.Normal(e.X, e.Y, e.Z);
                    gl.TexCoord(i / (double)n, 2 * j / (double)n);
                    gl.Vertex(p.X, p.Y, p.Z);
                }
                gl.End();
            }
        }

        /// <summary>
        /// Handles the OpenGLDraw event of the openGLControl control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="RenderEventArgs"/> instance containing the event data.</param>
        private void openGLControl_OpenGLDraw(object sender, RenderEventArgs e)
        {
            //  Get the OpenGL object.
            gl = openGLControl.OpenGL;

            //  Clear the color and depth buffer.
            gl.Clear(OpenGL.GL_COLOR_BUFFER_BIT | OpenGL.GL_DEPTH_BUFFER_BIT);

            //  Load the identity matrix.
            gl.LoadIdentity();

            //  Rotate around the Y axis.
            ////gl.Rotate(rotation, 0.0f, 1.0f, 0.0f);

            foreach (var item in atomsList)
            {
              //  Point3d coord = item.Coordinate;
                drawSphere(item.Coordinate, 0.75f, 20);
            }
            

            //  Nudge the rotation.
            rotation  = 30.0f;
        }

My aim is to draw something like this --

However, my output is something like the following --

Probably, the hidden surface removal is not working as expected.

• How can I obtain my expected output?

CodePudding user response：

The winding order of your primitives appears to be clockwise. The default winding order is counterclockwise (see Face Culling). Change the winding order that defines front-facing polygons:

gl.Enable(OpenGL.GL_CULL_FACE);
gl.CullFace(OpenGL.GL_BACK);
gl.FrontFace(OpenGL.GL_CW);