With the release last month of HDX 3D for Professional Graphics as a feature of XenDesktop, Citrix now offers two alternatives for delivering high-end 3D graphics from hosted applications. Let's compare these two solutions.

HDX 3D Pro Graphics on XenDesktop

Our premier solution for 3D professional graphics is based on hosted Windows desktops and works with either the XenDesktop 3 or XenDesktop 4 Desktop Delivery Controller. HDX 3D Pro Graphics features our most advanced technologies for data compression, making XenDesktop the best solution on the market for delivering 3D graphics to remote workers. For top level performance, we offer GPU-based compression, leveraging NVIDIA graphics processors with 96 or more CUDA cores. The compression level is automatically adjusted based on bandwidth. Just below that is CPU-based JPEG XR compression (no special GPU required). JPEG XR (the 'XR' stands for 'Extended Range'), formerly known as HD Photo, is an ISO/IEC standard for high dynamic range image encoding. These compression options are supported by the HDX 3D online plug-in for Windows, a special version of the ICA client. With advanced compression and other clever innovations, HDX 3D Pro Graphics delivers a good experience even at 2 Mbps and 200 ms roundtrip latency. And, of course, it delivers a high definition "like local" experience on high bandwidth, low latency connections.

Application compatibility is excellent with HDX 3D Pro Graphics because the applications run on a standard Windows XP operating system (and Windows 7 support is in development). It doesn't matter whether the applications use DirectX/Direct3D or OpenGL or whatever. HDX 3D supports True Color, important when a very large number of colors, shades, and hues need to be displayed, as with high quality photographic images or complex graphics. Customers are already using HDX 3D to work with models with more than a million parts, and 64-bit OS support is coming soon, which will enable huge amounts of memory to be addressed.

These comments from our customers sum it up best:
• So far this is the only product to have anywhere near acceptable performance
• Everyone is loving it
• 50 to 75% better than our existing solution
• In pure Swedish, it is "sh$@#ing good"!
• At 1.5 Mbps it is still very usable
• We have been extremely impressed

HDX 3D on XenApp for Windows Server 2008

For many organizations, HDX 3D on XenApp provides a great solution for delivering professional graphics, since Windows Server 2008 now enables a graphics card to be used for 3D rendering on Terminal Services / Remote Desktop Services. While hardware acceleration is limited to DirectX/Direct3D-based applications, that may be all you need depending on the specific applications your end users require. OpenGL based applications are CPU-rendered but they perform much faster on 64-bit Windows than on 32-bit so you may find that to be adequate. Of course, if you really need hardware acceleration for your OpenGL applications, go with HDX 3D Pro Graphics on XenDesktop.

Compression options with HDX 3D on XenApp are not quite as extensive as on XenDesktop but are generally sufficient for intracontinental WAN access. The highest level of compression is obtained by selecting Heavyweight JPEG, a special variant of JPEG that uses arithmetic encoding instead of the normal Huffman encoding. It gives a further reduction in bandwidth of around 10 to 20% without changing the pixel quality at all (compared to standard JPEG), at the cost of higher CPU consumption. With Progressive Display, users get a responsive experience even over WAN/Internet connections because images are delivered with lossier compression while being moved and quickly resolve to full resolution when motion stops.

A single graphics card in the server can support multiple concurrent users, depending on their usage characteristics. I spoke with a customer using an entry-level NVIDIA FX 370 GPU and they support four concurrent users on an HP 360 G5 server with a dual-core Xeon processor and 4 GB of memory running 32-bit Windows Server. They estimate that they will be able to support 12 to 16 simultaneous users on a dual quad-core server with 64-bit Windows Server and 32 GB of memory. Again, it depends on the application and the work profile of the users. A more powerful GPU, like the NVIDIA FX 5600 or 5800, will help with scalability, too.

HDX 3D on XenApp supports lossless compression (important in Healthcare), but color depth with DirectX hardware acceleration is currently limited to 16-bit High Color. True Color support (16 million colors) is offered with CPU-based rendering, and True Color with GPU hardware acceleration is planned for the near future, making HDX 3D on XenApp a great option for delivering PACS applications over hospital campus networks.

A Look Ahead

How will these technologies evolve in the future? 64-bit Windows XP and Windows 7 support is planned for HDX 3D Pro Graphics on XenDesktop, and True Color support is coming soon for HDX 3D on XenApp. Windows Server 2008 R2 is likely to bring some benefits, too. And as the graphics and hypervisor vendors introduce GPU virtualization, we expect to leverage that on both XenApp and XenDesktop; some exciting progress in this area is already happening in the lab. Expanding the VM Hosted Apps feature of XenApp to encompass 3D graphics apps would be a natural step.

Tell Us about Your Experience with HDX 3D

If you're using either of the HDX 3D technologies described above, I'm sure other customers would like to hear your story. Please tell us about the 3D applications you deliver, your data center and network, and how your users are benefiting.

Derek Thorslund
Citrix Product Strategist, HDX

    Three years ago, one of our premier customers came to us and asked us to build a platform that would allow them to deliver 3D applications remotely. There were a few products in the market at that time, both software and hardware based, that could support remote access for 3D graphics. But all of them required at least 5Mbps and latencies below 75 milliseconds. The customer's requirement was for us to build a solution that provided a usable experience with 2Mbps of bandwidth and tolerate up to 150ms round trip latency.    Thus began our journey to create the best 3D virtualization platform. The project has had many names over the years:  Pictor, Apollo and Prism. We have invested hundreds of man-years of effort and filed multiple patents. Today I am proud to say that we have accomplished what we set out to do three years ago. We have created XenDesktop 4 - a breakthrough desktop virtualization platform for 3D graphics.

    3D graphical applications, like CATIA, Pro/ENGINEER, Autodesk, etc. are used daily by CAD/CAM designers in the manufacturing sector. Research scientists use 3D graphical applications for oil exploration in Oil and Natural Gas companies. These are computationally challenging applications that need high end GPUs (graphical processing units) manufactured by companies like nVIDIA and AMD. These applications often require the most advanced workstations - fastest possible CPU and GPU and the largest amount of memory.

    3D applications are difficult to virtualize because performance is key in these applications. The CPU-GPU interaction has been designed to optimally deliver the highest number of frames per second (fps). Any software that is inserted in the middle can reduce the fps delivered to the user and cause a poor user experience. For example, for some complex models with hundreds of thousands of rendering triangles the workstation may create 2-3 frames per second. If the virtualization platform reduces the display rate to 1-2 fps, the difference is perceptible, and the end user will not want to use the application.

    In XenDesktop 4, we have extended the latency tolerance optimizations already presented in our HDX technology and added a few new compression algorithms, including some that use the GPU itself to do compression. The result is a 3D virtualization platform that meets the market requirements and delivers the best possible user experience. On the LAN, our solution can perform even better than locally installed applications, because server side GPUs can be more powerful than desktop GPUs. On the WAN there is no other solution that can deliver a usable experience at 2Mbps with 150 ms round trip latency.

    You will see this technology platform bear fruit in other areas that affect larger numbers of users. The new Microsoft OS - Windows 7  - leverages the GPU to deliver cool 3D graphical user interfaces. Our experience with high-end 3D graphics will help us effectively solve these problems for millions of users as they migrate to Windows 7. Stay tuned.