/// <summary>
        /// Create the shader program for label display in the openGL thread.
        /// This method will be called when WorldRenderManager's OnSurfaceCreated.
        /// </summary>
        /// <param name="labelBitmaps">View data indicating the plane type.</param>
        public void Init(List <Bitmap> labelBitmaps)
        {
            ShaderUtil.CheckGlError(TAG, "Init start.");
            if (labelBitmaps.Count == 0)
            {
                Log.Debug(TAG, "No bitmap.");
            }
            CreateProgram();
            int idx = 0;

            GLES20.GlGenTextures(textures.Length, textures, 0);
            foreach (Bitmap labelBitmap in labelBitmaps)
            {
                // for semantic label plane
                GLES20.GlActiveTexture(GLES20.GlTexture0 + idx);
                GLES20.GlBindTexture(GLES20.GlTexture2d, textures[idx]);

                GLES20.GlTexParameteri(
                    GLES20.GlTexture2d, GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
                GLES20.GlTexParameteri(
                    GLES20.GlTexture2d, GLES20.GlTextureMagFilter, GLES20.GlLinear);
                GLUtils.TexImage2D(GLES20.GlTexture2d, 0, labelBitmap, 0);
                GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
                GLES20.GlBindTexture(GLES20.GlTexture2d, 0);
                idx++;
                ShaderUtil.CheckGlError(TAG, "Texture loading");
            }
            ShaderUtil.CheckGlError(TAG, "Init end.");
        }
        /// <summary>
        /// Initialize the OpenGL ES rendering related to face geometry,
        /// including creating the shader program.
        /// This method is called when FaceRenderManager's OnSurfaceCreated method calling.
        /// </summary>
        /// <param name="context">Context.</param>
        public void Init(Context context)
        {
            ShaderUtil.CheckGlError(TAG, "Init start.");
            int[] texNames = new int[1];
            GLES20.GlActiveTexture(GLES20.GlTexture0);
            GLES20.GlGenTextures(1, texNames, 0);
            mTextureName = texNames[0];

            int[] buffers = new int[BUFFER_OBJECT_NUMBER];
            GLES20.GlGenBuffers(BUFFER_OBJECT_NUMBER, buffers, 0);
            mVerticeId  = buffers[0];
            mTriangleId = buffers[1];

            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, mVerticeId);
            GLES20.GlBufferData(GLES20.GlArrayBuffer, mVerticeBufferSize * BYTES_PER_POINT, null, GLES20.GlDynamicDraw);
            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, 0);

            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, mTriangleId);

            // Each floating-point number occupies 4 bytes.
            GLES20.GlBufferData(GLES20.GlElementArrayBuffer, mTriangleBufferSize * 4, null,
                                GLES20.GlDynamicDraw);
            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, 0);
            GLES20.GlBindTexture(GLES20.GlTexture2d, mTextureName);

            CreateProgram();

            //Add texture to facegeometry.
            Bitmap       textureBitmap = null;
            AssetManager assets        = context.Assets;

            try
            {
                Stream sr = assets.Open("face_geometry.png");
                textureBitmap = BitmapFactory.DecodeStream(sr);
            }
            catch (Exception e)
            {
                Log.Debug(TAG, " Open bitmap error!");
            }


            GLES20.GlTexParameteri(GLES20.GlTexture2d, GLES20.GlTextureWrapS, GLES20.GlClampToEdge);
            GLES20.GlTexParameteri(GLES20.GlTexture2d, GLES20.GlTextureWrapT, GLES20.GlClampToEdge);
            GLES20.GlTexParameteri(GLES20.GlTexture2d, GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
            GLES20.GlTexParameteri(GLES20.GlTexture2d, GLES20.GlTextureMagFilter, GLES20.GlLinear);
            GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
            GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
            GLES20.GlBindTexture(GLES20.GlTexture2d, 0);
            ShaderUtil.CheckGlError(TAG, "Init end.");
        }
        /// <summary>
        /// Allocates and initializes OpenGL resources needed by the plane renderer.  Must be
        /// called on the OpenGL thread, typically in
        /// <see cref="GLSurfaceView.IRenderer.OnSurfaceCreated(IGL10, Javax.Microedition.Khronos.Egl.EGLConfig)"/>
        /// </summary>
        /// <param name="context">Needed to access shader source and texture PNG.</param>
        /// <param name="gridDistanceTextureName">Name of the PNG file containing the grid texture.</param>
        public void CreateOnGlThread(Context context, String gridDistanceTextureName)
        {
            int vertexShader = ShaderUtil.LoadGLShader(TAG, context,
                                                       GLES20.GlVertexShader, Resource.Raw.plane_vertex);
            int passthroughShader = ShaderUtil.LoadGLShader(TAG, context,
                                                            GLES20.GlFragmentShader, Resource.Raw.plane_fragment);

            mPlaneProgram = GLES20.GlCreateProgram();
            GLES20.GlAttachShader(mPlaneProgram, vertexShader);
            GLES20.GlAttachShader(mPlaneProgram, passthroughShader);
            GLES20.GlLinkProgram(mPlaneProgram);
            GLES20.GlUseProgram(mPlaneProgram);

            ShaderUtil.CheckGLError(TAG, "Program creation");

            // Read the texture.
            var textureBitmap = Android.Graphics.BitmapFactory.DecodeStream(
                context.Assets.Open(gridDistanceTextureName));

            GLES20.GlActiveTexture(GLES20.GlTexture0);
            GLES20.GlGenTextures(mTextures.Length, mTextures, 0);
            GLES20.GlBindTexture(GLES20.GlTexture2d, mTextures[0]);

            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMagFilter, GLES20.GlLinear);
            GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
            GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
            GLES20.GlBindTexture(GLES20.GlTexture2d, 0);

            ShaderUtil.CheckGLError(TAG, "Texture loading");

            mPlaneXZPositionAlphaAttribute = GLES20.GlGetAttribLocation(mPlaneProgram,
                                                                        "a_XZPositionAlpha");

            mPlaneModelUniform = GLES20.GlGetUniformLocation(mPlaneProgram, "u_Model");
            mPlaneModelViewProjectionUniform =
                GLES20.GlGetUniformLocation(mPlaneProgram, "u_ModelViewProjection");
            mTextureUniform       = GLES20.GlGetUniformLocation(mPlaneProgram, "u_Texture");
            mLineColorUniform     = GLES20.GlGetUniformLocation(mPlaneProgram, "u_lineColor");
            mDotColorUniform      = GLES20.GlGetUniformLocation(mPlaneProgram, "u_dotColor");
            mGridControlUniform   = GLES20.GlGetUniformLocation(mPlaneProgram, "u_gridControl");
            mPlaneUvMatrixUniform = GLES20.GlGetUniformLocation(mPlaneProgram, "u_PlaneUvMatrix");

            ShaderUtil.CheckGLError(TAG, "Program parameters");
        }
        private void InitGlTextureData(Context context)
        {
            ShaderUtil.CheckGlError(TAG, "Init gl texture data start.");
            Bitmap       textureBitmap = null;
            AssetManager assets        = context.Assets;

            try
            {
                var sr = assets.Open("AR_logo.png");
                textureBitmap = BitmapFactory.DecodeStream(sr);
            }
            catch (Exception e)
            {
                Log.Debug(TAG, " Open Bitmap Error! ");
                return;
            }

            ShaderUtil.CheckGlError(TAG, "bitmap error.");
            GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
            GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
            GLES20.GlBindTexture(GLES20.GlTexture2d, 0);
            textureBitmap.Recycle();
            ShaderUtil.CheckGlError(TAG, "Init gl texture data end.");
        }
        /**
         * Creates and initializes OpenGL resources needed for rendering the model.
         *
         * @param context Context for loading the shader and below-named model and texture assets.
         * @param objAssetName  Name of the OBJ file containing the model geometry.
         * @param diffuseTextureAssetName  Name of the PNG file containing the diffuse texture map.
         */
        public void CreateOnGlThread(Context context, string objAssetName, string diffuseTextureAssetName)
        {
            // Read the texture.
            var textureBitmap = BitmapFactory.DecodeStream(context.Assets.Open(diffuseTextureAssetName));

            GLES20.GlActiveTexture(GLES20.GlTexture0);
            GLES20.GlGenTextures(mTextures.Length, mTextures, 0);
            GLES20.GlBindTexture(GLES20.GlTexture2d, mTextures[0]);

            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMagFilter, GLES20.GlLinear);
            GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
            GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
            GLES20.GlBindTexture(GLES20.GlTexture2d, 0);

            textureBitmap.Recycle();

            ShaderUtil.CheckGLError(TAG, "Texture loading");

            // Read the obj file.
            var objInputStream = context.Assets.Open(objAssetName);
            var obj            = ObjReader.Read(objInputStream);

            // Prepare the Obj so that its structure is suitable for
            // rendering with OpenGL:
            // 1. Triangulate it
            // 2. Make sure that texture coordinates are not ambiguous
            // 3. Make sure that normals are not ambiguous
            // 4. Convert it to single-indexed data
            obj = ObjUtils.ConvertToRenderable(obj);

            // OpenGL does not use Java arrays. ByteBuffers are used instead to provide data in a format
            // that OpenGL understands.

            // Obtain the data from the OBJ, as direct buffers:
            IntBuffer   wideIndices = ObjData.GetFaceVertexIndices(obj, 3);
            FloatBuffer vertices    = ObjData.GetVertices(obj);
            FloatBuffer texCoords   = ObjData.GetTexCoords(obj, 2);
            FloatBuffer normals     = ObjData.GetNormals(obj);

            // Convert int indices to shorts for GL ES 2.0 compatibility
            ShortBuffer indices = ByteBuffer.AllocateDirect(2 * wideIndices.Limit())
                                  .Order(ByteOrder.NativeOrder()).AsShortBuffer();

            while (wideIndices.HasRemaining)
            {
                indices.Put((short)wideIndices.Get());
            }
            indices.Rewind();

            var buffers = new int[2];

            GLES20.GlGenBuffers(2, buffers, 0);
            mVertexBufferId = buffers[0];
            mIndexBufferId  = buffers[1];

            // Load vertex buffer
            mVerticesBaseAddress  = 0;
            mTexCoordsBaseAddress = mVerticesBaseAddress + 4 * vertices.Limit();
            mNormalsBaseAddress   = mTexCoordsBaseAddress + 4 * texCoords.Limit();
            int totalBytes = mNormalsBaseAddress + 4 * normals.Limit();

            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, mVertexBufferId);
            GLES20.GlBufferData(GLES20.GlArrayBuffer, totalBytes, null, GLES20.GlStaticDraw);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mVerticesBaseAddress, 4 * vertices.Limit(), vertices);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mTexCoordsBaseAddress, 4 * texCoords.Limit(), texCoords);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mNormalsBaseAddress, 4 * normals.Limit(), normals);
            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, 0);

            // Load index buffer
            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, mIndexBufferId);
            mIndexCount = indices.Limit();
            GLES20.GlBufferData(
                GLES20.GlElementArrayBuffer, 2 * mIndexCount, indices, GLES20.GlStaticDraw);
            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, 0);

            ShaderUtil.CheckGLError(TAG, "OBJ buffer load");

            int vertexShader = ShaderUtil.LoadGLShader(TAG, context,
                                                       GLES20.GlVertexShader, Resource.Raw.object_vertex);
            int fragmentShader = ShaderUtil.LoadGLShader(TAG, context,
                                                         GLES20.GlFragmentShader, Resource.Raw.object_fragment);

            mProgram = GLES20.GlCreateProgram();
            GLES20.GlAttachShader(mProgram, vertexShader);
            GLES20.GlAttachShader(mProgram, fragmentShader);
            GLES20.GlLinkProgram(mProgram);
            GLES20.GlUseProgram(mProgram);

            ShaderUtil.CheckGLError(TAG, "Program creation");

            mModelViewUniform           = GLES20.GlGetUniformLocation(mProgram, "u_ModelView");
            mModelViewProjectionUniform =
                GLES20.GlGetUniformLocation(mProgram, "u_ModelViewProjection");

            mPositionAttribute = GLES20.GlGetAttribLocation(mProgram, "a_Position");
            mNormalAttribute   = GLES20.GlGetAttribLocation(mProgram, "a_Normal");
            mTexCoordAttribute = GLES20.GlGetAttribLocation(mProgram, "a_TexCoord");

            mTextureUniform = GLES20.GlGetUniformLocation(mProgram, "u_Texture");

            mLightingParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_LightingParameters");
            mMaterialParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_MaterialParameters");

            ShaderUtil.CheckGLError(TAG, "Program parameters");

            Android.Opengl.Matrix.SetIdentityM(mModelMatrix, 0);
        }
        public void CreateOnGlThread(Context context, string objAssetName, string diffuseTextureAssetName)
        {
            // Read the texture.
            var textureBitmap = BitmapFactory.DecodeStream(context.Assets.Open(diffuseTextureAssetName));

            GLES20.GlActiveTexture(GLES20.GlTexture0);
            GLES20.GlGenTextures(mTextures.Length, mTextures, 0);
            GLES20.GlBindTexture(GLES20.GlTexture2d, mTextures[0]);

            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
            GLES20.GlTexParameteri(GLES20.GlTexture2d,
                                   GLES20.GlTextureMagFilter, GLES20.GlLinear);
            GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
            GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
            GLES20.GlBindTexture(GLES20.GlTexture2d, 0);

            textureBitmap.Recycle();

            ShaderUtil.CheckGLError(TAG, "Texture loading");

            // Read the obj file.
            var objInputStream = context.Assets.Open(objAssetName);
            var obj            = JavaGl.Obj.ObjReader.Read(objInputStream);

            obj = JavaGl.Obj.ObjUtils.ConvertToRenderable(obj);

            IntBuffer   wideIndices = JavaGl.Obj.ObjData.GetFaceVertexIndices(obj, 3);
            FloatBuffer vertices    = JavaGl.Obj.ObjData.GetVertices(obj);
            FloatBuffer texCoords   = JavaGl.Obj.ObjData.GetTexCoords(obj, 2);
            FloatBuffer normals     = JavaGl.Obj.ObjData.GetNormals(obj);

            ShortBuffer indices = ByteBuffer.AllocateDirect(2 * wideIndices.Limit())
                                  .Order(ByteOrder.NativeOrder()).AsShortBuffer();

            while (wideIndices.HasRemaining)
            {
                indices.Put((short)wideIndices.Get());
            }
            indices.Rewind();

            var buffers = new int[2];

            GLES20.GlGenBuffers(2, buffers, 0);
            mVertexBufferId = buffers[0];
            mIndexBufferId  = buffers[1];

            mVerticesBaseAddress  = 0;
            mTexCoordsBaseAddress = mVerticesBaseAddress + 4 * vertices.Limit();
            mNormalsBaseAddress   = mTexCoordsBaseAddress + 4 * texCoords.Limit();
            int totalBytes = mNormalsBaseAddress + 4 * normals.Limit();

            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, mVertexBufferId);
            GLES20.GlBufferData(GLES20.GlArrayBuffer, totalBytes, null, GLES20.GlStaticDraw);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mVerticesBaseAddress, 4 * vertices.Limit(), vertices);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mTexCoordsBaseAddress, 4 * texCoords.Limit(), texCoords);
            GLES20.GlBufferSubData(
                GLES20.GlArrayBuffer, mNormalsBaseAddress, 4 * normals.Limit(), normals);
            GLES20.GlBindBuffer(GLES20.GlArrayBuffer, 0);

            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, mIndexBufferId);
            mIndexCount = indices.Limit();
            GLES20.GlBufferData(
                GLES20.GlElementArrayBuffer, 2 * mIndexCount, indices, GLES20.GlStaticDraw);
            GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, 0);

            ShaderUtil.CheckGLError(TAG, "OBJ buffer load");

            int vertexShader = ShaderUtil.LoadGLShader(TAG, context,
                                                       GLES20.GlVertexShader, Resource.Raw.object_vertex);
            int fragmentShader = ShaderUtil.LoadGLShader(TAG, context,
                                                         GLES20.GlFragmentShader, Resource.Raw.object_fragment);

            mProgram = GLES20.GlCreateProgram();
            GLES20.GlAttachShader(mProgram, vertexShader);
            GLES20.GlAttachShader(mProgram, fragmentShader);
            GLES20.GlLinkProgram(mProgram);
            GLES20.GlUseProgram(mProgram);

            ShaderUtil.CheckGLError(TAG, "Program creation");

            mModelViewUniform           = GLES20.GlGetUniformLocation(mProgram, "u_ModelView");
            mModelViewProjectionUniform =
                GLES20.GlGetUniformLocation(mProgram, "u_ModelViewProjection");

            mPositionAttribute = GLES20.GlGetAttribLocation(mProgram, "a_Position");
            mNormalAttribute   = GLES20.GlGetAttribLocation(mProgram, "a_Normal");
            mTexCoordAttribute = GLES20.GlGetAttribLocation(mProgram, "a_TexCoord");

            mTextureUniform = GLES20.GlGetUniformLocation(mProgram, "u_Texture");

            mLightingParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_LightingParameters");
            mMaterialParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_MaterialParameters");

            ShaderUtil.CheckGLError(TAG, "Program parameters");

            Android.Opengl.Matrix.SetIdentityM(mModelMatrix, 0);
        }