// Demonstrate buffer feedback AND geo shader add vertex/dump vertex

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            Closed += ShaderTest_Closed;

            gl3dcontroller = new Controller3D();
            gl3dcontroller.PaintObjects = ControllerDraw;
            gl3dcontroller.ZoomDistance = 100F;
            gl3dcontroller.MatrixCalc.PerspectiveNearZDistance = 0.1f;
            glwfc.BackColor = Color.FromArgb(0, 0, 60);
            gl3dcontroller.Start(glwfc, new Vector3(0, 0, 0), new Vector3(120f, 0, 0f), 1F);

            gl3dcontroller.KeyboardTravelSpeed = (ms, eyedist) =>
            {
                return((float)ms / 20.0f);
            };

            IGLTexture array2d = items.Add(new GLTexture2DArray(new Bitmap[] { Properties.Resources.mipmap, Properties.Resources.mipmap2,
                                                                               Properties.Resources.mipmap3, Properties.Resources.mipmap4 }, SizedInternalFormat.Rgba8, 9), "2DArray2");

            if (true)
            {
                items.Add(new GLMultipleTexturedBlended(false, 2), "ShaderPos");
                items.Shader("ShaderPos").StartAction += (s, m) =>
                {
                    array2d.Bind(1);
                };

                Vector4[] instancepositions = new Vector4[4];
                instancepositions[0] = new Vector4(-25, 0, -40, 0);      // last is image index..
                instancepositions[1] = new Vector4(-25, 0, 0, 0);
                instancepositions[2] = new Vector4(-25, 0, 40, 2);
                instancepositions[3] = new Vector4(-25, 0, 80, 2);

                GLRenderState rt = GLRenderState.Tri(cullface: false);
                rObjects.Add(items.Shader("ShaderPos"),
                             GLRenderableItem.CreateVector4Vector2Vector4(items, PrimitiveType.Triangles, rt,
                                                                          GLSphereObjectFactory.CreateTexturedSphereFromTriangles(3, 20.0f),
                                                                          instancepositions, ic: 4, separbuf: true
                                                                          ));
            }

            // Shader MAT

            if (true)
            {
                IGLProgramShader smat = items.Add(new GLMultipleTexturedBlended(true, 2), "ShaderMat");
                smat.StartAction += (s, m) =>
                {
                    array2d.Bind(1);
                };

                Matrix4[] pos2 = new Matrix4[3];
                pos2[0]     = Matrix4.CreateRotationY(-80f.Radians());
                pos2[0]    *= Matrix4.CreateTranslation(new Vector3(25, 0, -40));
                pos2[0].M44 = 0;        // this is the image number

                pos2[1]     = Matrix4.CreateRotationY(-70f.Radians());
                pos2[1]    *= Matrix4.CreateTranslation(new Vector3(25, 0, 0));
                pos2[1].M44 = 2;        // this is the image number

                pos2[2]     = Matrix4.CreateRotationZ(-60f.Radians());
                pos2[2]    *= Matrix4.CreateTranslation(new Vector3(25, 0, 40));
                pos2[2].M44 = 0;        // this is the image number

                GLRenderState rq = GLRenderState.Quads(cullface: false);
                rObjects.Add(items.Shader("ShaderMat"),
                             GLRenderableItem.CreateVector4Vector2Matrix4(items, PrimitiveType.Quads, rq,
                                                                          GLShapeObjectFactory.CreateQuad(20.0f, 20.0f, new Vector3(-90f.Radians(), 0, 0)), GLShapeObjectFactory.TexQuadCW,
                                                                          pos2, ic: 3, separbuf: false
                                                                          ));
            }

            items.Add(new GLMatrixCalcUniformBlock(), "MCUB");      // def binding of 0
        }