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Embed 3D models (U3D) in PDF files using C#

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Sample C# code for using PDFTron SDK to embed U3D content (3 dimensional models) in PDF files. Learn more about our C# PDF Library.

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// Copyright (c) 2001-2021 by PDFTron Systems Inc. All Rights Reserved.

using System;
using pdftron;
using pdftron.Common;
using pdftron.Filters;
using pdftron.SDF;
using pdftron.PDF;

using NUnit.Framework;

namespace MiscellaneousSamples
	/// <summary>
	/// This example illustrates how to embed U3D content in PDF. 
	/// Some parameters used to center 3D model are assumed.
	/// </summary>
	public class U3DTest

		// Relative path to the folder containing test files.
		const string input_path =  "TestFiles/";

		public static void Sample()

				using (PDFDoc doc = new PDFDoc())
					Page page = doc.PageCreate();
					Obj annots = doc.CreateIndirectArray();
					page.GetSDFObj().Put("Annots", annots);

					Create3DAnnotation(doc, annots);
					doc.Save(Utils.CreateExternalFile("dice_u3d.pdf"), SDFDoc.SaveOptions.e_linearized);
			catch (PDFNetException e)

		static void Create3DAnnotation(PDFDoc doc, Obj annots)
			// ---------------------------------------------------------------------------------
			// Create a 3D annotation based on U3D content. PDF 1.6 introduces the capability 
			// for collections of three-dimensional objects, such as those used by CAD software, 
			// to be embedded in PDF files.
			Obj link_3D = doc.CreateIndirectDict();
			link_3D.PutName("Subtype", "3D");

			// Annotation location on the page
			Rect bbox = new Rect(25, 180, 585, 643);
			link_3D.PutRect("Rect", bbox.x1, bbox.y1, bbox.x2, bbox.y2);

			// The 3DA entry is an activation dictionary (see Table 9.34 in the PDF Reference Manual) 
			// that determines how the state of the annotation and its associated artwork can change.
			Obj activation_dict_3D = link_3D.PutDict("3DA");

			// Set the annotation so that it is activated as soon as the page containing the 
			// annotation is opened. Other options are: PV (page view) and XA (explicit) activation.
			activation_dict_3D.PutName("A", "PO");

			// Embed U3D Streams (3D Model/Artwork).
            MappedFile u3d_file = new MappedFile(Utils.GetAssetTempFile(input_path + "dice.u3d"));
			FilterReader u3d_reader = new FilterReader(u3d_file);

			Obj u3d_data_dict = doc.CreateIndirectStream(u3d_reader);
			u3d_data_dict.PutName("Subtype", "U3D");
			link_3D.Put("3DD", u3d_data_dict);

			// Set the initial view of the 3D artwork that should be used when the annotation is activated.
			Obj view3D_dict = link_3D.PutDict("3DV");			
			view3D_dict.PutString("IN", "Unnamed");
			view3D_dict.PutString("XN", "Default");
			view3D_dict.PutName("MS", "M");
			view3D_dict.PutNumber("CO", 27.5);

			// A 12-element 3D transformation matrix that specifies a position and orientation 
			// of the camera in world coordinates.
			Obj tr3d = view3D_dict.PutArray("C2W");
			tr3d.PushBackNumber(1); tr3d.PushBackNumber(0); tr3d.PushBackNumber(0); 
			tr3d.PushBackNumber(0); tr3d.PushBackNumber(0); tr3d.PushBackNumber(-1);
			tr3d.PushBackNumber(0); tr3d.PushBackNumber(1); tr3d.PushBackNumber(0); 
			tr3d.PushBackNumber(0); tr3d.PushBackNumber(-27.5); tr3d.PushBackNumber(0);			

			// Create annotation appearance stream, a thumbnail which is used during printing or
			// in PDF processors that do not understand 3D data.
			Obj ap_dict = link_3D.PutDict("AP");
			ElementBuilder builder = new ElementBuilder();
			ElementWriter writer = new ElementWriter();

				Image.Create(doc, Utils.GetAssetTempFile(input_path + "dice.jpg")), 
					   0, 0, bbox.Width(), bbox.Height()));

			Obj normal_ap_stream = writer.End();
			normal_ap_stream.PutName("Subtype", "Form");
			normal_ap_stream.PutRect("BBox", 0, 0, bbox.Width(), bbox.Height());
			ap_dict.Put("N", normal_ap_stream);