private void InitOpengl(int width, int height)
    {
      m_vpWidth  = width;
      m_vpHeight = height;
      float ratio = (float)width / height;

      m_projMatrix = Matrix4.CreateOrthographicOffCenter(-1, 1, -1, 1, 1f, 100f);
      m_viewMatrix = Matrix4.LookAt(Vector3.UnitZ, Vector3.Zero, Vector3.UnitY);
      m_mvpMatrix  = m_projMatrix * m_viewMatrix;// Matrix4.Mult(m_viewMatrix, m_projMatrix);

      m_shaderPrograms = new ArrayList();

      string vertexLineShaderSrc =
        @"attribute vec3 vertex_position;
        uniform mat4 mvp;
        void main()
        {
          gl_Position = mvp * vec4(vertex_position, 1.0);
        }";
      string fragLineShaderSrc =
        @"void main()
        {
          gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
        }";

      ShaderProgram lineShader = ShaderProgram.CreateShaderProgram(vertexLineShaderSrc, fragLineShaderSrc, () => { GL.DrawArrays(BeginMode.Lines, 0, verts.Length); });
      if (lineShader != null)
      {
        lineShader.AddAttributeLocationData(new AttributeLocationData(lineShader.ShaderProgramId,
          "vertex_position",
          () =>
          {
            int vertexPosAttrib = GL.GetAttribLocation(lineShader.ShaderProgramId, "vertex_position");
            GL.EnableVertexAttribArray(vertexPosAttrib);
            GL.VertexAttribPointer(vertexPosAttrib, 3, VertexAttribPointerType.Float, false, 0, verts);
          }));
        lineShader.AddUniformLocationData(new UniformLocationData(lineShader.ShaderProgramId,
          "mvp",
          () =>
          {
            int mvpUniform = GL.GetUniformLocation(lineShader.ShaderProgramId, "mvp");
            GL.UniformMatrix4(mvpUniform, false, ref m_mvpMatrix);
          }));
        m_shaderPrograms.Add(lineShader);
      }
    }